# Pressure cookers and canners: research notes

Date: 2026-10-25. Scope: stovetop pressure cookers (including pressure pans and braisers), stovetop pressure canners and cooker/canners, and non-pressure canners (boiling-water canners and atmospheric steam canners); not electric pressure cookers, multicookers or electric canners (Presto Precise, Ball FreshTech), which sit in `machines > appliances > electric_cookers`; not plain stockpots used as water baths (sibling `saucepans`, "Saucepans, Stock Pots & Dutch Ovens"); not jars, lids, jar lifters or canning kits, which have no leaf in the supplies kitchen group and are left out here.

Overlaps named: a 20-quart enamel stockpot sold with a jar rack as a "water bath canner" is in scope because it is sold as a canner; the same pot sold as a stockpot belongs to `saucepans`. Electric multicookers come up constantly in buyer questions ("can I can in my Instant Pot?") and are answered by one judgement, but their products belong to the machines leaf.

Quote labels: **verbatim** = the sentence in quotation marks was in text I read myself (pdftotext on a downloaded PDF, or curl plus HTML stripping into the scratchpad); **fetched excerpt** = the WebFetch tool returned the page as a model summary, with the quoted words in quotation marks; **search excerpt** = from a search-engine summary. No search excerpts were used: this session's WebSearch budget was already spent (200 of 200) when the run started, so every source below was reached by known URL or by following links from fetched pages (site sitemaps, link lists).

## Seed

Seed output, verbatim:

```
=== Example entry (from an unrelated category) ===
category: car-tyres
what this shows: a number that is on every listing and still needs a judgement attached, because experts know it only compares within one manufacturer's range.

<example>
{
  "id": "treadwear_grade",
  "label": "Treadwear grade",
  "definition": "A number moulded on the tyre's side, from a US test, that estimates how long the tread lasts relative to a reference tyre set at 100.",
  "why_experts_care": "A 600 should last roughly twice as long as a 300, which is the single biggest driver of cost per mile. The catch experts repeat is that each manufacturer runs its own test, so the number is reliable for comparing tyres within one brand and loose across brands. Softer, grippier tyres sit low on this scale on purpose.",
  "kind": "numeric",
  "unit": "grade",
  "range": { "min": 60, "max": 1000, "typical": "Most everyday tyres sit between 300 and 700." },
  "roles": ["annotation", "sort_key"],
  "novice_answerable": false,
  "source": "listing",
  "listing_field_hint": "Listed as UTQG, usually as three values together, for example 500 A A. Treadwear is the first.",
  "backfill_cost": "low",
  "backfill_note": "If absent from the listing, the manufacturer's spec sheet always has it.",
  "visual": { "chartable": true, "encoding": "position on a horizontal scale, with the grip grade as a second mark so the trade-off shows" },
  "priority": { "narrows_set": 3, "cost_to_answer": 3 },
  "evidence": ["nhtsa_utqg", "tirerack_explainer"]
}
</example>

Judgement that would accompany it:
{
  "claim": "Treadwear grades can be compared across brands as a rough guide but not as a ranking.",
  "confidence": "high",
  "sources_disagree": true,
  "note": "The regulator describes the test as standard. Specialist reviewers say manufacturers calibrate differently. We side with the reviewers because they test the tyres."
}

=== Persona ===
A tailor, who thinks in fit, drape and what you can alter afterwards

Ask yourself two things and write the answers under 'Seed' in notes.md:
  1. What is the pressure-cookers equivalent of the example above?
  2. What would this persona notice first about pressure-cookers that a typical buyer would not?
Keep what survives the data check. Drop the rest.
```

1. **The treadwear equivalent is the pressure number, "15 PSI".** It is the one figure every pressure cooker has, it is real (UL 136 caps household cookers at "a nominal pressure of 15 psig (103 kPa) or less", verbatim), and it does not compare cleanly across makers. Hip Pressure Cooking (verbatim) separates "Operating Pressure – the pressure at which the pressure cooker cooks the food" from "Valve Release Pressure – the pressure at which the main regulating valve releases pressure (2 to 4 psi more than the operating pressure depending on the manufacturer)", and says European spring-valve cookers are "about 13 psi" while "European manufactured pressure cookers are designed to cook at 1 bar or 100 kpa ... 14.5 psi (this is rounded up to 15 psi)". So, like treadwear, the number is comparable within one maker's line and loose across makers, and units differ by region (psi, bar, kPa). **Kept** as `operating_pressure_psi` with a judgement. The 2 to 4 psi gap and the 13 psi figure have one source each, so they stay here and the JSON says only that a printed valve figure may be a release point and that some European cookers run lower. A second treadwear-like number turned up: capacity. European and Asian cookers are sized in litres and "rounded down to quarts" (Hip, verbatim), so a "6 quart" may be 6.34 quarts. **Kept** inside `capacity_qt`.
2. **The tailor notices fit first, then what can be altered.** Fit, three ways: whether the jars fit (a canner's quart count is what USDA tests; the 16-quart and 23-quart Presto canners both take 7 quarts and differ only in pints, 10 versus 20, verbatim from Presto's pages; All American's 10.5-quart takes 4 regular quarts but only 3 wide-mouth, verbatim from the All American chart); whether the canner fits the stove (Presto: "A fully loaded 16-quart canner may exceed 40 pounds; a fully loaded 23-quart canner may exceed 50 pounds", verbatim; All American retailer: the 930 and 941 "are too heavy and too wide for glass-top stoves", verbatim); and whether the cooker fits the household (about one quart or litre per person, Hip and Hawkins). Alterations: the gasket and overpressure plug are the parts that wear and get replaced (Presto, Hip, Wikipedia), a dial gauge can be tested and adjusted or replaced (USDA: "Replace gauges that differ by more than 2 pounds", verbatim), and weighted regulators come in 5, 10 and 15 psi pieces (All American page, verbatim "5, 10, 15 psi"; USDA on weighted gauges at 5, 10 or 15). **Kept**: `jar_capacity_quarts`, `jar_capacity_pints`, `usda_canner_size`, `stove_compatibility`, `seal_type`, `gauge_type`. **Dropped**: height clearance under a range hood (All American retailer only; eyeballable from the listed height); a "convertible regulator kit" facet for dial-gauge canners (no source fetched); spare-parts availability as its own facet (it is a brand attribute; folded into `seal_type`'s note).

## Sources and what each supports

### Regulators, standards bodies and food-safety extension

**USDA Complete Guide to Home Canning, Guide 1: Principles of Home Canning (2015 revision), via NCHFP (pdftotext)**
https://nchfp.uga.edu/papers/guide/GUIDE01_HomeCan_rev0715.pdf
- verbatim: "Low-acid foods have pH values higher than 4.6. They include red meats, seafood, poultry, milk, and all fresh vegetables except for most tomatoes." "Acid foods have a pH of 4.6 or lower. They include fruits, pickles, sauerkraut, jams, jellies, marmalades, and fruit butters."
- verbatim: "all low-acid foods should be sterilized at temperatures of 240° to 250°F, attainable with pressure canners operated at 10 to 15 PSIG."
- verbatim: "Steam canners are not currently recommended because processing times for use with current models are still being researched. It is not recommended that pressure processes in excess of 15 PSI be applied when using new pressure canning equipment."
- verbatim: "Most are designed to hold seven quart jars or eight to nine pints. Small pressure canners hold four-quart jars; some large pressure canners hold 18 pint jars in two layers, but hold only seven quart jars. Pressure saucepans with smaller volume capacities are not recommended for use in canning."
- verbatim: "Low-acid foods must be processed in a pressure canner to be free of botulism risks. Although pressure canners may also be used for processing acid foods, boiling water canners are recommended for this purpose because they are faster."
- verbatim (boiling-water canners): "These canners are made of aluminum or porcelain-covered steel." "at least 1 inch of briskly boiling water will be over the tops of jars" "A flat bottom must be used on an electric range. Either a flat or ridged bottom can be used on a gas burner." "the canner should be no more than 4 inches wider in diameter than the element on which it is heated."
- verbatim (pressure canners): "They have a jar rack, gasket, dial or weighted gauge, an automatic vent/cover lock, a vent port (steam vent) to be closed with a counterweight or weighted gauge, and a safety fuse." "At sea level, a canner operated at a gauge pressure of 10.5 lbs provides an internal temperature of 240°F." "all types of pressure canners must be vented 10 minutes before they are pressurized."
- verbatim: "Weighted-gauge models exhaust tiny amounts of air and steam each time their gauge rocks or jiggles during processing. They control pressure precisely and need neither watching during processing nor checking for accuracy." "The single disadvantage of weighted-gauge canners is that they cannot correct precisely for higher altitudes. At altitudes above 1,000 feet, they must be operated at canner pressures of 10 instead of 5, or 15 instead of 10, PSI."
- verbatim: "Check dial gauges for accuracy before use each year." "Pressure adjustments can be made if the gauge reads up to 2 pounds high or low. Replace gauges that differ by more than 2 pounds."
- verbatim: "Use only canners that have the Underwriter's Laboratory (UL) approval to ensure their safety."
- The guide's worked example (peaches, dial gauge) steps the pressure 6, 7, 8, 9 lb across the altitude bands 0–2,000, 2,001–4,000, 4,001–6,000 and 6,001–8,000 ft (table text scrambled by pdftotext but these figures are legible).
- Supports: the acidity split, the 4-quart minimum, the 240 to 250 °F requirement, weighted versus dial gauges, yearly testing, UL approval, boiling-water canner stove rules. Confidence high.

**NCHFP NewsFlash, "Canning in Pressure Cookers" (September 2015; curl)**
https://nchfp.uga.edu/newsflash/canning-in-pressure-cookers
- verbatim: "USDA does not have recommended processes for canning in a small pressure cooker. The recommendation for using USDA pressure processes for low-acid foods is to use a canner that holds at least four (4) quart-size jars standing upright on the rack, with the lid in place. The research for USDA pressure processes for vegetable and meat products was conducted in pressure canners that are most similar to today's 16-quart or larger pressure canners."
- verbatim: "Pressure cookers have less metal, are smaller in diameter, and will use less water than pressure canners. The result is that the time it takes a canner to come up to processing pressure (that is, the come-up time) and the time it takes the canner to cool naturally down to 0 pounds pressure ... will be less than for the standard pressure canner."
- verbatim: "in the late 1980s the USDA published its recommendation to not use pressure saucepans (small cookers) for home canning."
- verbatim: "the canner should have a way to follow recommended venting procedures to remove air from inside the canner before it is pressurized, and to indicate that the canner remains at least at the target pressure throughout the entire process time."
- Supports: second source for the 4-quart rule (same institution as the guide, different document), the come-up/cool-down mechanism, the "means to indicate pressure" condition. Confidence high.

**NCHFP NewsFlash, "Canning in Electric Multi-Cookers" (1 February 2019; curl)**
https://nchfp.uga.edu/publications/nchfp/factsheets/electric_cookers.html
- verbatim: "we do not support the use of the USDA canning processes in the electric, multi-cooker appliances now containing "canning" or "steam canning" buttons on their front panels." "Our recommendations were determined for stovetop pressure canners which hold four or more quart-size jars standing upright." "What matters is temperature, not pressure."
- Supports: the multicooker judgement and the third statement of the 4-quart rule. Confidence high.

**NCHFP NewsFlash, "Using Atmospheric Steam Canners" (24 August 2020; curl)**
https://nchfp.uga.edu/newsflash/using-atmospheric-steam-canners
- verbatim: "Atmospheric steam canners are used for processing naturally acid or properly acidified foods with natural or equilibrated pH values of 4.6 or below. They are not pressurized vessels used for processing for low-acid foods."
- verbatim: "Processing times must be adjusted for elevation, and must also be 45 minutes or less, including any elevation modification. The processing time is limited by the amount of water the canner base will hold, and the canner cannot be opened to add water".
- Cites Willmore, Etzel, Andress and Ingham (2015), Food Protection Trends 35(3).
- Supports: steam canners approved for acid foods only, 45-minute cap; disagreement with the 2015 USDA guide. Confidence high.

**University of Wisconsin–Madison Extension (Winnebago County), "A fresh look at steam canning" (30 July 2020; curl)**
https://winnebago.extension.wisc.edu/2020/07/30/a-fresh-look-at-steam-canning/
- verbatim: "The atmospheric steam canner uses only ~2 quarts of water (compared to 16 quarts, or more, in a boiling water canner)". "Processing time can be no more than 45 minutes." "a vigorously boiling canner can boil dry within 20 minutes". "Extension doesn't recommend using any of the multi-cookers for home canning." "jars should not be stacked in the canner" (boiling-water or steam).
- Supports: second source for the 45-minute cap and for steam canners being acid-only; no stacking in non-pressure canners. Confidence high.

**UL Standards & Engagement, UL 136 Pressure Cookers (Edition 8, published 16 June 2009, last revised 11 March 2026; curl of the catalog page)**
https://www.shopulstandards.com/ProductDetail.aspx?productId=UL136
- verbatim scope: "These requirements cover household-type cooking utensils known as pressure cookers or pressure sauce pans which operate at a nominal pressure of 15 psig (103 kPa) or less. They are intended for use over gas- or electric-top burners of residential-type cooking ranges." "These requirements do not cover pressure cookers intended for pressure frying with oil."
- verbatim: "This revision to ANSI/UL 136 dated March 11, 2026 includes the following changes in requirements for the Cover Misalignment Test".
- Supports: the 15 psi ceiling, UL listing as the US safety facet. The full standard text was not read (paywalled). Confidence high for scope.

**FDA, Letter to retailers and distributors of cookware (12 December 2024; WebFetch, fetched excerpt; curl was blocked)**
https://www.fda.gov/food/environmental-contaminants-food/letter-retailers-and-distributors-cookware
- fetched excerpt (quoted): "certain imported cookware may leach lead (Pb) into food" made from "aluminum, brass, and aluminum alloys known as Hindalium/Hindolium or Indalium/Indolium"; retailers should "confirm that such products do not leach lead into food". Names Rashko Baba Co. Ltd. on import alert. The summary says the letter does not mention pressure cookers by name.
- Supports: the lead judgement, with King County for the pressure-cooker specifics. Confidence high for the letter's existence and wording; medium for exact wording since it is a summary.

**Public Health – Seattle & King County, "Cookware that released lead above the FDA's recommended daily intake levels" (pdftotext)**
https://cdn.kingcounty.gov/-/media/king-county/depts/dph/documents/health-safety/environmental-health/toxins/cookware-releasing-lead.pdf
- verbatim method: "We added a dilute acid solution equivalent to household vinegar (4% acetic acid) to the cookpots and simmered for 15 minutes." Compared against FDA's Interim Reference Level "for children (2.2 ug/day)".
- verbatim rows: "Rashko Baba Pressure Cooker (Aluminum) Afghanistan Etsy.com (MenGrills) 5/6/2021 ... 48.8** 1,580**"; "Hamza Baba Pressure Cooker (Aluminum) Afghanistan Amazon.com 5/22/2023 ... 45.75** 990**"; "Kitchen King Pressure Cooker (Aluminum) ... 3.53* 530**" (µg per 250 mL at 15 min and 24 h). Eight of the table's rows are aluminium pressure cookers.
- Supports: the lead judgement; aluminium pressure cookers bought on Amazon and Etsy were among the worst. Confidence high.

### Primers and enthusiast references

**Wikipedia, Pressure cooking (curl)**
https://en.wikipedia.org/wiki/Pressure_cooking
- verbatim table: "1.0 bar (15 psi) 121 °C (250 °F) 23%" (cooking time versus boiling), "0.7 bar (10 psi) 116 °C (241 °F)", "0 bar (0 psi) 100 °C (212 °F)".
- verbatim: first generation "operate with a weight-modified or "jiggler" valve, which releases pressure during operation"; second generation "operate with a spring-loaded valve that is often hidden from view in a proprietary mechanism. ... characterized by two or more pressure settings. Some of these pressure cookers do not release any steam during operation (non-venting)".
- verbatim: "Pressure cookers are available in different capacities ... with 6 litres' capacity being common." "maximum fill levels ... two-thirds full with solid food, half full for liquids and foods that foam and froth".
- verbatim: "Gasket/sealing rings need replacing with a new one about once a year (or sooner if it is damaged". "Aluminum pressure cookers may be stamped, polished, or anodized, but all are unsuitable for the dishwasher. They are cheaper, but the aluminum is reactive to acidic foods". "Some aluminum pressure cookers from Afghanistan are known to be contaminated with lead and imported pots were responsible for the lead poisoning of Afghani refugees in Washington state in 2019."
- Supports: the pressure–temperature scale, generations of valve, fill limits, gasket interval, aluminium versus stainless. Confidence medium (encyclopedia; numbers cross-checked against Presto and USDA).

**Hip Pressure Cooking (Laura Pazzaglia), Pressure Cooker PSI FAQ (curl)**
https://www.hippressurecooking.com/pressure-cooker-psi-faq-the-stuff-you-didnt-think-to-ask/
- verbatim: "the maximum operating pressure for American Pressure Cookers (15 psi) and the maximum operating pressure for most modern European Cookers (which is about 13 psi for spring-valve type cookers)."
- verbatim: "European manufactured pressure cookers are designed to cook at 1 bar or 100 kpa (metric pressure measurements) and that translates to 14.5 psi (this is rounded up to 15 psi)". (The page gives both 13 and 14.5 psi for European cookers; I use neither as a number in the JSON.)
- verbatim: "Operating Pressure – the pressure at which the pressure cooker cooks the food. Valve Release Pressure – the pressure at which the main regulating valve releases pressure (2 to 4 psi more than the operating pressure depending on the manufacturer)."
- verbatim: "Increase pressure cooking time by 5% for every 1000 ft above 2000 ft elevation".
- Supports: operating versus release pressure, regional pressure differences, the seed answer. Confidence medium (one expert author; the site's sitemap now also carries casino spam posts, a sign of compromise, but the articles cited are her older content and internally consistent).

**Hip Pressure Cooking, Pressure Cooker Sizes and Types (curl)**
https://www.hippressurecooking.com/pressure-cooker-sizes-and-types/
- verbatim: "We recommend getting the smallest pressure cooker to fit your needs because a bigger the pressure cooker will take longer to reach pressure, will need more liquid to get there and it will be bulky to both clean and store."
- verbatim: "a small 2qt pressure pan only needs about 1/2 cup of liquid (or less) to reach pressure a much larger 12qt pressure cooker needs two cups (or more)!"
- verbatim bands: "2-3qt - SMALL ... Great for one to two people." "6-8qt - STANDARD ... Great for a family of 4-6." "10qt or larger - Pressure Cooker/ CANNER ... According to the USDA a stove top pressure cooker can be used as a canner if it can hold at least four quart-sized jars."
- verbatim (author reply in comments): "Presto ONLY makes venting weight-controlled cookers" and "Kuhn Rikon, Fagor, WMF and Fissler ONLY make spring-valve cookers. Magefesa makes both." "I, personally, do not recommend using weighted cookers because they are less energy efficient, they evaporate more cooking liquid and technically, they do not maintain a constant temperature".
- Supports: size bands, smallest-that-fits rule, maker-to-valve mapping. Confidence medium.

**Hip Pressure Cooking, Pressure Cooker Buying Guide (curl)**
https://www.hippressurecooking.com/pressure-cooker-buying-guide/
- verbatim: "Our rule of thumb (with extra wiggle room) is to calculate 1 quart/liter per person in the household. So a 6 qt will feed maximum 6 people". "Pressure cookers made by European and Asian manufacturers are actually sized in liters, not quarts."
- verbatim: "Spring-valve non-venting cookers have the latest pressure-regulating technology and they won't fill your kitchen with the sounds of steam engine pistons firing (like old-style venting cookers)". "Stove top cookers should be made of stainless steel because cheaper aluminum cookers are not only soft and easily deformed but they are "reactive"". "A pressure cooker should have at least two pressure settings." "Don't be dazzled by new pressure cookers that have 10 or more pressure settings – no recipes have actually been written for all of those other pressure settings." "the sealing gaskets (the silicone ring in the lid) usually last 18-24 months".
- verbatim: "There are various workarounds and hacks to use a dedicated pressure canner for cooking – but we do not recommend doing so". "Pressure cookers made more than 20 years ago do not have the fool-proof safety features of modern pressure cookers".
- Supports: one quart per person, spring valve preference, two settings, gasket interval, canner-as-cooker disagreement. Confidence medium.

**Hip Pressure Cooking, Pressure Cooker Capacity FAQ (curl)**
https://www.hippressurecooking.com/pressure-cooker-capacity-faq-if-it-fits-cook-it/
- verbatim: "Pressure Cookers should only be filled to half when cooking beans, rice & grains and two-thirds for everything else." "A pressure cooker's maximum capacity is, in fact, a safety feature. In order for a pressure cooker to receive UL rating, their manual must contain text to this effect." "a weight-modified or jiggler-type valve must release pressure and steam rhythmically to maintain a set pressure. The extra venting means that a longer cooking time will evaporate more liquid".
- verbatim: "if it's made in Europe or China, even if the size is stated in quarts, the pressure cooker is really 6L (which is actually 6.34 quarts)."
- Supports: fill limits, usable-volume metric, venting and evaporation. Confidence medium.

**Hip Pressure Cooking, cooktop and induction articles (curl)**
https://www.hippressurecooking.com/is-your-cook-top-sabotaging-the-pressure-cooker-how-gas-induction-and-electric-cooktops-affect-pressure-cooking/ and https://www.hippressurecooking.com/7-dos-donts-of-pressure-cooking-with-induction/
- verbatim: "Induction cook tops can bring a cooker up to pressure 60% faster than gas – that's in just 4 1/2 minutes instead of 11 starting with a "cold" cooker." (three runs, 6 L Magefesa, 1 kg water). "The magnetic field induces (or forces) an electric current into the base of the cookware".
- Supports: induction behaviour (trimmed detail only; single test). Confidence medium.

**Hip Pressure Cooking, Kuhn Rikon Duromatic review (curl)**
https://www.hippressurecooking.com/pressure-cooker-review-kuhn-rikon-duromatic-excellent/
- verbatim: "When the first red ring on the bar is seen, it means that it has reached "Low Pressure" when the second red ring displays it means that it has reached "High Pressure"." "Primary over-pressure release valve – Integrated in the pressure signal, activates to release pressure if the pressure cooker reaches 17.4 PSI."
- Supports: how a spring valve shows pressure (definition text); an example of release pressure above 15. Confidence medium.

### Spec sheets and brand pages

**Presto 23-Quart Pressure Canner and Cooker, 01781, product page and spec sheet (curl; pdftotext)**
https://www.gopresto.com/product/presto-23-quart-pressure-canner-01781 and https://www.gopresto.com/uploads/SS_01781.pdf
- verbatim: "Mason Jar Capacity: 26 Half-Pints, 20 Pints, 7 Quarts." "23-Quart liquid capacity (21.8 liters)" "This pressure canner is designed for use on household range burners of 12,000 BTUs or less." "Constructed of extra-strong, warp-resistant aluminum and suitable for use on regular and smooth-top ranges." "Doubles as a boiling water canner".
- verbatim spec sheet table: pressure canning regular/wide mouth: half-pints 26/16, pints 20/16, quarts 7/7; boiling water: half-pints 13/8, pints 10/8, quarts 7/7. "Capacity will vary depending on style of jar." "Out of Box: ... Weight 10.32 lb". "Handy as a large-capacity pressure cooker too!"
- Supports: jar counts, wide versus regular mouth, single layer for boiling water, Presto's view that a canner also cooks. Confidence high (maker's own sheet).

**Presto 16-Quart Pressure Canner, 01755 (curl)**
https://www.gopresto.com/product/presto-16-quart-pressure-canner-01755
- verbatim: "Mason Jar Capacity: 13 Half-Pints, 10 Pints, 7 Quarts*." "*Pints and half-pints only for boiling water method." "16-Quart liquid capacity (15.1 liters)".
- Supports: 16 and 23 quart canners hold the same 7 quarts. Confidence high.

**Presto 23-Quart Induction Compatible Pressure Canner, 01784 (curl)**
https://www.gopresto.com/product/23-quart-induction-compatible-pressure-canner-with-stainless-steel-clad-base-01784
- verbatim: "The only full-sized consumer pressure canner that works on an induction range." "Works on gas, electric, smooth-top, and induction ranges.* Constructed of heavy-gauge polished aluminum with a stainless steel-clad base". "*May not work on all portable induction ranges."
- Supports: induction needs a clad base; induction canners are rare (maker's claim, not verified). Confidence medium.

**Presto Pressure Canner instruction book 01755/01781 (pdftotext)**
https://www.gopresto.com/uploads/01755_01781_72_719M_Canner_Eng_Web_Inst_Book_CL%5B3%5D.pdf
- verbatim: "The pressure regulator acts as a safety device to prevent pressure in excess of 15 pounds from building in the canner. Pressure readings are registered only on the pressure dial gauge."
- verbatim: "It is recommended that the sealing ring and overpressure plug be replaced at least every 3 years." "Before each canning season, have the dial gauge checked for accuracy".
- verbatim: "A fully loaded 16-quart canner may exceed 40 pounds; a fully loaded 23-quart canner may exceed 50 pounds." "If using a smooth-top range, refer to the range's owner's manual for weight limits".
- verbatim altitude chart (tomatoes, dial gauge): "2,001–4,000 ft. 12 pounds / 4,001–6,000 ft. 13 pounds / 6,001–8,000 ft. 14 pounds"; recipes "Process at 11 pounds pressure" at 2,000 ft or below.
- Supports: Presto canners are dial-gauge, yearly testing (second source), gasket interval, loaded weight, 1 psi altitude steps (second source with the USDA example). Confidence high.

**Presto 6-Quart Stainless Steel (01362) and 6-Quart Aluminum (01264) pressure cookers, product pages and instruction book (curl; pdftotext)**
https://www.gopresto.com/product/6-quart-stainless-steel-pressure-cooker-01362, https://www.gopresto.com/product/presto-6-quart-aluminum-pressure-cooker-01264, https://www.gopresto.com/uploads/72_856D_AL_SS_Cookers_Eng_Web_Instructions%5B5%5D.pdf
- verbatim (stainless): "$ 102.99" "Luxurious stainless steel construction with tri-clad base" "Works on gas, electric, smooth-top, and induction ranges." "Fully immersible and dishwasher safe with the sealing ring and over-pressure plug removed." "6-Quart Liquid Capacity (5.7 liters)."
- verbatim (aluminium): "$ 59.99" "Strong, heavy-gauge aluminum" "Works on electric, smooth-top, and gas ranges." "Fully immersible with the sealing ring and over-pressure plug removed." (no dishwasher, no induction)
- verbatim (manual): "At 15 pounds of pressure, a temperature of 250°F (or 121°C) is reached inside the pressure cooker." "Do not fill pressure cooker over ⅔ full. When cooking foods that foam, froth, or expand, such as rice, grains, dry beans, peas, and lentils, or foods that are mostly liquid, such as soup, never fill the cooker over ½ full." "It is recommended that the sealing ring and overpressure plug be replaced at least every two years." "When normal operating pressure is reached, the pressure regulator will begin to rock."
- Supports: aluminium versus stainless (induction, dishwasher, price), 15 psi to 121 °C (second source with Wikipedia), fill limits (second source), Presto cookers are weighted-valve (rocking regulator), gasket interval. Confidence high.

**All American 1930 (Wisconsin Aluminum Foundry), 921 and 910 product pages (curl)**
https://www.allamerican1930.com/products/the-921-pressure-cooker and https://www.allamerican1930.com/products/the-910-pressure-cooker
- verbatim: "crafted from heavy-duty cast aluminum ... Featuring a precision metal-to-metal sealing system with no gasket to replace". "5, 10, 15 psi". "Gas, electric, flat-top stoves". "Equipped with a pressure regulator weight to vent steam, a gauge for visual monitoring, and an overpressure plug for added safety."
- Supports: metal-to-metal seal, weighted regulator plus monitoring dial, 5/10/15 psi weights. Confidence high.

**All American Canner Comparison Chart, Red Hill General Store (authorized retailer since 1998; curl)**
https://www.allamericancanner.com/All-American-Pressure-Canners-Comparison-Chart.htm
- verbatim: 910 "10 1/2 Quarts", "Regular Quart Jar 4-5", "Wide Mouth Quart Jar 3", "Regular Pint Jar 7", empty weight "12 Pounds"; 915 15.5 qt, 7 quarts, "9-10" pints, 15 lb; 921 21.5 qt, 7 quarts, "18 (stacked x 2)" pints, 18 lb; 925 25 qt, 7 quarts, 18 pints, 4 half-gallon, 19 lb; 930 30 qt, 14 quarts, 23 lb; 941 41.5 qt, 19 regular quarts, 32 pints, 34 lb.
- verbatim: "The 930 and 941 are too heavy and too wide for glass-top stoves." "Typical flat-top stove weight limits are 50-60 pounds. The weights listed are empty. Add 20–30 lbs for water and jars in the 910–925, and 40–50 lbs in the 930 and 941." "You need a canner that fits at least four quart jars upright — that's the USDA minimum". "only pint and quart jars have been tested and approved by the USDA for pressure canning."
- Supports: jar counts by size, wide-mouth edge case, glass-top limits (the 50 to 60 lb limit is single source and stays here), the double-stack pattern. Confidence medium-high (retailer reproducing maker specs; numbers match the maker's 921/910 pages where both show them).

**All American 1930, 910 Pressure Cooker/Canner product page (WebFetch, 2026-10-25, added after the blind check)**
https://www.allamerican1930.com/products/the-910-pressure-cooker
- fetched excerpt: "4 Regular Mouth, 4 Wide Mouth" quart jars for the 910 (against the retailer chart's "3" wide-mouth). The same page's size table gives the 941 "22" quarts and the 921 "17.75 Pounds" empty, matching the 921 maker page's own table.
- Supports: corrects the 910 wide-mouth figure and the 941 quart figure (see judgement on All American sourcing). Confidence high (maker's own page, fetched twice with consistent figures).

**Hawkins Cookers pressure cooker catalogue (India; pdftotext)**
https://www.hawkinscookers.com/download/PC_Catalog.pdf
- verbatim size chart (Classic): "1.5 LITRE ... 1 OR 2 PERSONS", "2 LITRE ... 2 OR 3 PERSONS", "3 LITRE WIDE ... 3 OR 4 PERSONS", "4 LITRE ... 4 TO 6 PERSONS", "5 LITRE ... 5 TO 7 PERSONS", "6.5 LITRE ... 7 TO 9 PERSONS", "8 LITRE ... 8 TO 11 PERSONS"; models to "12 LITRE".
- verbatim: "Each pressure cooker made by Hawkins features an inside-fitting lid." "Hawkins pressure cookers are listed by Underwriters Laboratories, USA ... CE certification also available." "quality-certified by the Bureau of Indian Standards (popularly known as ISI)." "improved Vent Weight (Whistle)". "Recommended for use on gas stoves." "The extra-thick induction compatible bottom allows the pressure cooker to work well on gas, induction". "All Hawkins pressure cookers are guaranteed for five years."
- Supports: roughly one litre per person (second source with Hip), Indian cookers are weighted (whistle), UL/CE/ISI as the safety marks buyers meet, aluminium cookers can be induction-capable with a thick base. Confidence high for the maker's own facts.

### Could not reach

Serious Eats (curl and WebFetch both refused), America's Test Kitchen (guessed URL returned a different review), Wirecutter and the Internet Archive (archive.org returned 429 Too Many Requests on every attempt, likely because many agents were fetching at once), Kuhn Rikon's site (JavaScript shell, 31 words), FDA pages by curl (blocked; WebFetch worked), several university extension URLs guessed without search (University of Minnesota, Penn State, Utah State, Oregon State all returned not-found shells). EN 12778 (the European pressure-cooker standard) could not be read, so the register names CE marking only. Amazon listings were not attempted; prior registers record that they block fetches.

## Data points used for derived metrics

- `usable_volume_qt`: two-thirds for most food and one-half for beans, grains, rice and soup (Presto cooker manual verbatim; Hip capacity FAQ verbatim; Wikipedia). For a 6-quart cooker: 4 quarts of stew, 3 quarts of beans.
- `people_served`: about one quart or litre per person as a ceiling (Hip: "6 qt will feed maximum 6 people"); Hawkins' chart is at or above one person per litre (4 L → 4 to 6, 5 L → 5 to 7, 8 L → 8 to 11). The metric uses capacity in litres as a rough maximum and says Hawkins is more generous.
- Size bands mapped to the capacity question in notes only: one or two people → 2 to 4 quarts (Hip 2–3 qt for one to two; Hawkins 1.5 to 2 L for one to three); about four → 4 to 6 quarts (Hawkins 4 L for 4 to 6; Hip 6 qt maximum 6); six or more → 8 quarts or more (Hip 8 qt maximum 8; Hawkins 6.5 to 8 L for 7 to 11).

## Against the existing add-on schema

Read: `supplies/kitchen/add-ons/pressure_cooker.jsonc` (`suitable_for_pressure_canning` boolean with the comment "safety hard gate — not all cookers can can", `max_psi`, `induction_compatible`, `sizing.jar_capacity_raw`), composed with `kitchen-standard.jsonc` (`materials[]` with roles, `max_heat_temp`, `dishwasher_safe`) and `supplies-standard.jsonc` (`high_signal_markdown`, `sizing.capacity`, `sizing.weight`, `sizing.dimensions`, `sizing.pack_count` and the rest). Kinds follow `zamana-expertise/AGENTS.md` rule 4 (vertical anchor, category quality currency, hard filter, sizing) and rule 5 (dead). Proposals only; nothing in zamana-expertise was edited.

| Facet in this register | In the schema today | Proposed kind | Note |
|---|---|---|---|
| vessel_type | no | hard filter | Proposal: `vessel_type` enum [pressure_cooker, pressure_canner, boiling_water_canner, steam_canner]. The leaf mixes pressurised and non-pressurised canners, and today nothing separates a water-bath pot from a pressure canner except `suitable_for_pressure_canning = false`, which a cooker also has. |
| usda_canner_size | yes, `suitable_for_pressure_canning` | hard filter (already) | Keep, and define it in the comment: true only for a stovetop vessel that holds at least four quart jars upright with the lid on and has a dial or weighted gauge (NCHFP). Fill it by that rule, never from the maker's "canning" claim, since multicookers with canning buttons claim it (NCHFP 2019). Rule 5 would call it derivable from jar count; keep it anyway as the safety gate, because the jar count is often missing on large cookers. |
| jar_capacity_quarts, jar_capacity_pints | partly, `sizing.jar_capacity_raw` (string) | sizing | Proposal: `sizing.jar_quarts` and `sizing.jar_pints` (numbers, regular-mouth, pressure method), keeping `jar_capacity_raw` for wide-mouth and boiling-water counts. They vary by size variant (Presto 16 vs 23 qt), so rule 2 puts them in sizing, and they are bought by number. |
| capacity_qt | yes, `sizing.capacity` (supplies-standard) | sizing (already) | Keep. Add to the comment that litre-sized imports labelled in quarts should be stored in litres as stated. |
| valve_type | no | hard filter | Proposal: `pressure_valve` enum [spring_valve, weighted_valve] for cookers; null for canners. It is the split reviewers sort cookers by and it is not visible in a photo. |
| gauge_type | no | hard filter | Proposal: `canner_gauge` enum [dial, weighted, weighted_plus_dial]. Decides yearly testing and altitude behaviour (USDA). Not reliably photographable (a dial is visible, but whether the weight or the dial governs is not). |
| operating_pressure_psi | yes, `max_psi` | category quality currency | Keep, but define as the highest operating pressure, not the valve-release figure, and convert bar or kPa (1 bar ≈ 14.5 psi). For canners, store the highest weight setting (15). |
| pressure_settings | no | high_signal_markdown | Not worth a field: "two settings, high and low" is a line of text. |
| body_material | yes, `materials[]` role `body` (kitchen-standard) | vertical anchor (already) | Keep. `aluminum` and `anodized_aluminum` exist; a clad base is `stainless_steel(body)` + `aluminum(core)`/`base`. |
| stove_compatibility | partly, `induction_compatible` | hard filter (already) | Keep the boolean. The glass-top weight limit for canners belongs in high_signal_markdown ("too heavy for glass-top"), not a field. |
| seal_type | partly, `materials[]` role `seal_gasket` | high_signal_markdown | No new field; "metal-to-metal, no gasket" is a markdown line, and the absence of a `seal_gasket` entry can carry it. |
| safety_listing | no | dead under rule 5 (certifications) | Goes to high_signal_markdown. The register keeps it as a facet because the brief requires the governing standard to be visible, and USDA tells buyers to use UL-approved canners. |

Schema fields this register considers noise for this leaf: `max_heat_temp` (pressure cookers are not oven pans; no source mentions an oven limit); `dishwasher_safe` (follows from body material: aluminium no, stainless usually yes, per Wikipedia and Presto, so rule 5 cuts it as derivable); `sizing.pack_count`, `sizing.pieces_included_text` (single vessels, occasionally a two-pot set); `segments.ingredients`. `sizing.weight` earns its place for canners only (glass-top limits).

## Branches

Every leg, with the sentence it rests on. Revised 2026-10-25 after the blind check; changed legs are marked.

- `vessel_type = Pressure cooker` → ask `valve_type`, `capacity_qt`, `body_material`; `gauge_type`, `jar_capacity_pints`, `jar_capacity_quarts`, `usda_canner_size` irrelevant. Ask: valve type is the cooker split (Hip: "Spring valve for Stovetop"; the maker-to-valve mapping). Capacity: Hip's size bands and one quart per person apply to cookers. Body material: Hip, Wikipedia and Presto all compare aluminium and stainless for cookers. Irrelevant: NCHFP "USDA does not have recommended processes for canning in a small pressure cooker", so jar counts (both quarts and pints) and the gauge (a canner part, USDA "dial or weighted gauge") do not matter to someone cooking meals. **CHANGED**: added `jar_capacity_quarts` to the irrelevant list; it was dropped alongside pints for cookers but had been left asked. SUPPORTED.
- `vessel_type = Pressure canner` → ask `jar_capacity_pints`, `gauge_type`, `stove_compatibility`, `safety_listing`; `valve_type` irrelevant. Ask: `jar_capacity_pints` replaces `jar_capacity_quarts` here, since the register itself says height (pints, stacked in two layers), not quart count, separates the big canners, and USDA/Presto/All American show almost every canner holding the same 7 quarts regardless of size; `jar_capacity_quarts` stays a derived input to `usda_canner_size` but is no longer asked directly, since asking it barely narrows anything. `safety_listing` is added because USDA tells buyers to use only UL-approved canners and the no-name canners that dominate the market are exactly where that bites. Irrelevant: canners regulate with a weighted gauge or a dial gauge plus a safety regulator (USDA; Presto manual; All American), and spring valves are a cooker-only mechanism (Wikipedia; Hip names only cooker makers), so `valve_type` does not apply. **CHANGED**: `pressure_settings` is no longer marked irrelevant. The blind check found canners do differ in regulator options (5/10/15 psi weights, fixed-cap dial regulators), and USDA's altitude rule makes that difference matter for safety; the register's own `gauge_type` values do not fully carry it, so the honest state is "not asked here, not ruled out" rather than a false claim of irrelevance. SUPPORTED.
- `vessel_type = Water-bath or steam canner` → ask `jar_capacity_quarts`, `stove_compatibility`; `gauge_type`, `valve_type`, `operating_pressure_psi`, `pressure_settings`, `seal_type`, `usda_canner_size` irrelevant. Ask: USDA "at least 1 inch of briskly boiling water will be over the tops of jars", so depth sets how many quarts fit; USDA "A flat bottom must be used on an electric range" and "no more than 4 inches wider in diameter than the element". Irrelevant: NCHFP "They are not pressurized vessels"; USDA describes boiling-water canners as having "removable perforated racks and fitted lids", not a sealed lid. Unchanged. SUPPORTED.
- `valve_type = Spring valve` → ask `operating_pressure_psi`, `pressure_settings`. Chain: (1) Hip: "Kuhn Rikon, Fagor, WMF and Fissler ONLY make spring-valve cookers", all European makers; (2) Hip: European cookers are rated in bar or kPa and some run below the American 15 psi, so the pressure figure needs checking against US recipe times; and Wikipedia: second-generation spring-valve cookers are "characterized by two or more pressure settings", so which settings it has is the next difference. SUPPORTED (chain).
- `valve_type = Weighted valve` → ask `operating_pressure_psi`, `pressure_settings`. **CHANGED (new leg)**. The blind check found the operating-pressure-versus-release-pressure problem is not specific to spring valves: Hip's PSI FAQ states it as a general distinction, and release figures printed above 15 psi appear on weighted and no-name cookers of every valve type, not only European spring-valve ones. Asking the same two facets on both branches is the honest fix, rather than a chain that singles out spring valves. SUPPORTED.
- Answer mapping for the vessel question, stated once (now also in `vessel_type`'s `backfill_note` in category.json, not only here): "weeknight meals" → Pressure cooker; "canning vegetables or meat" (and beans, stock, fish: any low-acid food, USDA pH above 4.6) → Pressure canner; "only jams and pickles" (and fruit, acidified tomatoes) → Water-bath or steam canner. A buyer who answers "both meals and canning" → Pressure canner, since only it does both safely (USDA: a pressure canner may also process acid foods; Presto sells its canner as a cooker too), with the judgement that Hip advises against a canner for daily meals.
- Considered and not written: `gauge_type = Dial gauge` → ask about testing: testing is a duty, not a product facet. `vessel_type = Pressure canner` → drop `body_material`: most canners are aluminium, but Presto's 01784 has a clad base for induction and `body_material` now also allows "Enamel on steel" and "Stainless steel" values that exist in the canner market; left out rather than claimed irrelevant.

## Numbers in category.json and how many sources stand behind each

| Number | Sources |
|---|---|
| pH 4.6 acid/low-acid line | USDA Guide 1 (verbatim); NCHFP steam canner page (verbatim) |
| At least four quart jars upright | USDA Guide 1; NCHFP pressure cooker NewsFlash; NCHFP multicooker NewsFlash; All American retailer chart; Hip sizes page |
| 15 psi ceiling | UL 136 scope ("15 psig (103 kPa) or less"); USDA ("not recommended that pressure processes in excess of 15 PSI"); Presto canner manual (regulator stops pressure above 15) |
| 15 psi → 121 °C / 250 °F | Presto cooker manual (verbatim); Wikipedia table |
| 240 to 250 °F at 10 to 15 psi for low-acid canning | USDA Guide 1 (verbatim); 10.5 psi → 240 °F (USDA); Wikipedia 10 psi → 241 °F |
| 1 bar ≈ 14.5 psi | Hip PSI FAQ; Wikipedia table (1.0 bar, 15 psi) |
| Fill 2/3, 1/2 for beans, grains, soup | Presto cooker manual; Hip capacity FAQ; Wikipedia |
| About one quart or litre per person | Hip buying guide; Hawkins size chart |
| 6 to 8 quart standard cooker; 6 litres common | Hip sizes and buying guide; Wikipedia ("6 litres' capacity being common") |
| Cookers 1.5 to 12 litres | Hawkins catalogue (1.5 to 12 L); Hip capacity FAQ ("from 1 to 12L") |
| 16 and 23 quart Presto both 7 quarts; 10 vs 20 pints | Presto 01755 and 01781 pages; USDA ("18 pint jars in two layers, but hold only seven quart jars") for the pattern |
| All American 910: 4 regular quarts, 4 wide-mouth (corrected from "3 wide-mouth" after the blind check) | Maker's 910 page, now rendering correctly on WebFetch (2026-10-25): "4 Regular Mouth, 4 Wide Mouth". Retailer chart's "3" is now treated as the contradicted figure, not the source. |
| Most canners hold 7 quarts | USDA ("Most are designed to hold seven quart jars"); Presto; All American chart |
| Weighted gauge 5/10/15; above 1,000 ft use 10 instead of 5, 15 instead of 10 | USDA (verbatim); All American maker page ("5, 10, 15 psi") |
| Dial gauge: test yearly; replace if off by more than 2 psi | USDA (verbatim, both); Presto manual ("Before each canning season") for the yearly test. The 2 psi figure is USDA only (primary document; kept). |
| Dial-gauge altitude steps of 1 psi | USDA worked example (6, 7, 8, 9 lb); Presto manual (11, 12, 13, 14 lb) |
| Loaded canner 40 to 50 lb or more | Presto manual (verbatim); All American chart (empty 15 to 19 lb plus 20 to 30 lb) |
| Water-bath: flat bottom on electric; ≤ 4 in wider than element | USDA Guide 1 only (primary document; kept as USDA's rule) |
| Steam canner ≤ 45 minutes, acid foods only | NCHFP 2020; UW–Madison Extension 2020 |
| Gasket replacement: about yearly / 18 to 24 months / at least every 2 years (cookers) / 3 years (canners) | Wikipedia; Hip; Presto cooker manual; Presto canner manual. Kept as a disagreement. |
| FDA lead letter, 12 December 2024 | FDA letter (fetched excerpt); FDA lead in foodwares page (fetched excerpt) |
| King County: aluminium pressure cookers on Amazon and Etsy leached lead above FDA reference levels | King County table (verbatim); Wikipedia (Afghan aluminium pressure cookers, Washington 2019) |
| Presto 6-qt stainless $102.99, aluminium $59.99 | Presto pages (maker's own prices on 2026-10-25; brand-specific, not generalised) |
| Presto 23-qt canner 10.32 lb out of box; All American 921 about 18 lb empty (17.75 lb by the maker's own table, corrected from the retailer chart after the blind check) | Presto spec sheet; All American's own 921 and 910 pages, each giving the same 17.75 lb in their size table |

## Dropped

- Minimum liquid by size (1/2 cup for a 2-quart, 2 cups for a 12-quart). Hip only, and manuals give their own minimums.
- Induction time-to-pressure (4.5 versus 11 minutes, 60 percent faster). One test by one author.
- The 2 to 4 psi gap between operating and valve-release pressure, and Kuhn Rikon's 17.4 psi release. Hip only; the JSON keeps the idea, not the numbers.
- High-altitude cooking adjustment (+5 percent per 1,000 ft above 2,000 ft). Hip and Wikipedia agree (Wikipedia: "approximately 5% for every 300 m (980 ft) above 610 m (2,000 ft)"), but it is about using the cooker, not choosing one.
- Lid style (inside-fitting Hawkins lid versus outside lids, centre screw, bolt-down). Real (Hawkins, Wikipedia), but no source says buyers should choose by it beyond Hawkins' own claim that it is safer.
- Half-gallon jar capacity. USDA has no pressure times for half-gallon jars (All American retailer: "only pint and quart jars have been tested"); kept as a note in `jar_capacity_quarts`'s backfill note.
- Burner limit of 12,000 BTU. Presto only, and an operating instruction; mentioned in trimmed detail.
- Pressure frying. UL 136 excludes it and Hip says it needs a different vessel; no products in this leaf.

## Trimmed detail

- `operating_pressure_psi`: Hip measured an Instant Pot's operating pressure at 11.6 psi against a 105 kPa (15.2 psi) valve marking; that is the clearest case of release versus operating pressure, but it is an electric cooker and out of scope.
- `stove_compatibility`: Presto says its canners are for "household range burners of 12,000 BTUs or less" and warns against outdoor LP burners, which warp the base. All American's 50 to 60 lb "typical flat-top stove weight limits" is the retailer's figure; the range's own manual governs.
- `gauge_type`: USDA notes the highest volume of trapped air is "in processing raw-packed foods in dial-gauge canners. These canners do not vent air during processing", which is why venting for 10 minutes is mandatory for all canners and especially dial-gauge ones.
- `vessel_type`: USDA gives the time cost of using a pressure canner for acid foods: about 12 to 15 minutes to vent, 10 minutes venting, 5 to pressurise, 8 to 10 processing and 20 to 60 cooling, against 25 to 60 minutes total for most acid foods in boiling water.
- `jar_capacity_pints`: for boiling-water use, Presto's 23-quart holds 10 regular pints (single layer) against 20 under pressure; the 16-quart holds pints and half-pints only by the boiling-water method, not quarts.
- `body_material`: Hip also advises against nonstick interiors in pressure cookers (scratches expose aluminium). One source; not a facet.

## Script problems

- `validate.py` rejects `"vertical": "supplies"`: the skill's `schema.json` enum is `formulations, machines, fashion, furnishing, other`, and the brief requires `supplies`. The delivered category.json keeps `supplies` as briefed, so validate reports exactly one schema error on `vertical`. A scratchpad copy with `"vertical": "other"` was validated to confirm everything else is clean. render.py and viewer.py accept `supplies` and were run separately (the brief's `&&` chain stops after validate). Scripts and schema were not modified. The same problem is recorded in `cookware-sets/notes.md`.

## Viewer check

`tests/viewer-browser.py` (Playwright, pyenv 3.11, offline) run on a scratchpad copy of `viewer.html`: PASS at 1380, 768 and 390 px in light and dark (6 of 6). The 1380 light first screen was read by the author: tree labels at full size, all thirteen facets on the priority map, no overflow.

## Corrections after the blind check (2026-10-25)

Verified independently by WebFetch on the maker's own pages (not a re-read of the checker's report): https://www.allamerican1930.com/products/the-910-pressure-cooker and https://www.allamerican1930.com/products/the-921-pressure-cooker, both 2026-10-25. Both confirm the maker's size table: 910 holds 4 regular and 4 wide-mouth quarts, 921 weighs 17.75 lb empty, 941 holds 22 quarts. New reference `allamerican_910` added; `allamerican_921` and `allamerican_chart` supports lists updated. WebSearch budget for this session was already spent when this run started (confirmed: 200 of 200), so no new web searches were available; every correction that needed a source used a URL already in the references list or a direct maker URL reached by its known slug, as notes.md's "Could not reach" section describes for the original research pass.

1. (Finding 1) Added a note to `gauge_type.backfill_note` and `why_experts_care` naming the fixed-cap-regulator-plus-dial pattern that fills the no-name 19 to 32 quart canner market, classified as "Dial gauge" (the same control pattern Presto's own canner manual describes: the regulator only caps pressure, the dial is read). Added `pressure_settings` back to the "not ruled irrelevant" state and `safety_listing` to the Pressure canner branch's `then_ask`. Did not add a fourth `gauge_type` value: the existing three values already cover a fixed-cap regulator as "Dial gauge" once the note states the pattern, and a new value would need a product-level survey this run could not do without search.
2. (Finding 2) Rewrote the weighted-gauge altitude sentence in `gauge_type.why_experts_care`, trade-off 3 and judgement 4's framing: above 1,000 ft a weighted gauge jumps to the next weight (10 to 15 psi) with no step between, not "where 10 would do", and dropped "which overprocesses food" since no cited source says that.
3. (Finding 3) Re-sourced the All American jar and weight figures to the maker's own pages (verified above): 910 is 4 regular + 4 wide-mouth quarts (not 3 wide-mouth), 941 is 22 quarts (not 19), 921 is 17.75 lb by the maker's table. Added a new judgement stating we follow the maker where the retailer chart and the maker disagree. Added `allamerican_910` to the evidence lists of `usda_canner_size` and `jar_capacity_quarts`.
4. (Finding 4) Reclassified `usda_canner_size.source` from `derived` to `researched` and its `backfill_cost` from `medium` to `high`, since no canner title in the market states a jar count. Raised `jar_capacity_quarts.backfill_cost` from `low` to `medium` and `valve_type.backfill_cost` from `low` to `medium`. Added a sentence to `vessel_type.backfill_note` stating the "Pressure canner" value cannot be read from titles that also call 3 to 8 quart cookers "canners".
5. (Finding 5) Swapped `jar_capacity_quarts` for `jar_capacity_pints` in the Pressure canner branch's `then_ask` (the register's own claim is that height, not quart count, separates big canners) and added the irrelevant quarts to the cooker branch instead (see Branches trace above). Added the "both meals and canning → Pressure canner" mapping to `vessel_type.backfill_note`.
6. (Finding 6) Reworded `gauge_type`'s split question from "Weighted gauge you never test, or dial gauge for finer altitude steps?" to "Above 1,000 feet, or willing to test a gauge yearly?", which a first-time buyer can answer without already knowing that altitude changes canning pressure. Updated the split's `rationale` and the facet's `cold_start_question` to match. Kept `novice_answerable: true`, since the new question only needs the buyer's own altitude and willingness, not a lecture.
7. (Finding 7) Rewrote `safety_listing.definition` and `why_experts_care`: UL 136's own scope names pressure cookers and sauce pans, not canners; UL approval for canners is stated as USDA's requirement, and UL 136 coverage of canners is not claimed as verified. Removed "the only outside check that the lid lock and backup valves work", which no fetched source supports.
8. (Finding 8) Added "Enamel on steel" to `body_material.values` and `listing_field_hint`, matching USDA's "porcelain-covered steel" for boiling-water canners. Removed "Nearly every canner is aluminium" from `why_experts_care`; replaced with a sentence naming enamel-on-steel water-bath canners and stainless pressure canners as real exceptions. Limited trade-off 6's "aluminium... gives up all three" to plain aluminium and named Hawkins' hard-anodised, induction-ready line as a middle option.
9. (Finding 9) Could not edit the sibling leaves (`electric_cookers`, `cookware-stove-accessories`, `saucepans`) or `zamana-expertise`, per this run's instructions, so the scope mismatches the checker found (electric canners not named by the `electric_cookers` label; canner racks and gaskets sent here but excluded; the stock-pot boundary keyed differently from `saucepans`) are logged here rather than fixed at the source. Added an "Out of scope" sentence to `vessel_type.backfill_note` naming electric canners, steam juicers, and canner racks or gaskets sold alone, so this register at least states its own boundary even where the sibling file does not match it.
10. (Finding 10) Rewrote `capacity_qt.backfill_note` to say the answer bands are ours, applying Hip's one-quart-per-person rule as a target, and fixed the middle band from "4 to 6 quarts" to "6 to 8 quarts" to match Hip's own sizes page, which puts a family of four at 6 to 8 quarts.
11. (Finding 11) In `vessel_type.why_experts_care`, attached "which USDA calls faster" to the water-bath canner only (USDA's own comparison is boiling-water canners against pressure canners) and gave the steam canner its own, separately sourced 45-minute cap instead of sharing the "faster" claim.
12. (Finding 12) Broadened `valve_type`'s branch: `operating_pressure_psi` and `pressure_settings` are now asked on both "Spring valve" and "Weighted valve" (new leg, see Branches trace), since the operating-versus-release-pressure problem is not specific to spring valves. Softened `operating_pressure_psi.why_experts_care` to give Hip's own range (13 to 14.5 psi) rather than one number, and to say the release-figure warning applies "whatever the valve type."
13. (Finding 13) Reworded `stove_compatibility.why_experts_care` so Presto's "only full-sized consumer pressure canner" claim reads as that maker's own claim about its own lineup, not a market fact, and acknowledged that many canners now ship with an induction-ready base.

Rejected or left unchanged, with reasons:
- The All American brand-to-valve and gauge sourcing issue (Hip's maker mapping comes from a comment reply, not the sizes-page body) is a real sourcing-transparency point, but the checker did not put it in "Required fixes," and the comment is still part of the cited page (`hip_sizes`). Left as is; flagging here for a future check.
- Did not add a new `gauge_type` categorical value for a "fixed-pressure regulator with a dial" canner class, for the reason given in item 1 above. If a future check or a product survey confirms this needs its own value rather than a note, that is a schema-adjacent change this register alone should not make without re-running validate/render/viewer against the wider facet set.
- Did not change `pressure_settings`'s own values, definition or roles to describe canner weight options (5/10/15 psi) directly; its "One / Two (high and low) / Three or more" framing is cooker-specific language, and relabeling it for canners without a source describing canner buyers choosing by "pressure settings" the same way would be an invented mapping. Removing it from the canner branch's `makes_irrelevant` list, without adding it to `then_ask`, was judged the more honest middle ground.
- Did not pursue the Amazon-listing claims in Part D (specific title counts such as "18 of 51" or "13 of 47") as new sourced facts in the JSON, since this run's WebSearch budget was exhausted and Amazon fetches were not attempted (notes.md's original research pass recorded that prior registers found Amazon blocks fetches); the backfill-cost and source reclassifications in item 4 above do not depend on those specific counts, only on the underlying claim (no canner title states a jar count), which is corroborated by `allamerican_chart`, `presto_01781` and `presto_01755` already giving maker-page jar counts that no competing title reproduces.