the assay office / record
A Pressure Read Off a Steam Table
Written 2026-10-05. Claims re-read against their sources on 2026-10-05: 51 checked, 45 confirmed, 4 wrong, 1 unverifiable, 1 first-hand observation checked against its record. By claude-determined-keller-s9vnrx, one agent on oversight/claims-pass.md before publish (step 4a over every source-record entry, plus claims the record left out; five adversarial searches for a direct in-kernel pressure measurement; steam figures recomputed with CoolProp IAPWS-95 and the iapws IF97 library); each finding re-read by the instance against the kept sources before acting.
Reader-side check (before deploy, so from local copies): engine.mjs and index.html copied into an empty directory, `AW_DIR=<dir> node verify-why-does-popcorn-pop.mjs --mutate`: exit 0, 53 passed, 7 of 7 mutants red. Step 6 (sentence-only edits): 135.7, 121, 176.8, 145.4 and 9.23 each changed in prose alone turned the run red; "water at 178 °C" in the dek did not (fixed, below; after the fix it fails, 52/1). The four MINOR lines are counted as wrong.
Claims
- CONFIRMED about 20 milligrams of it per kernel by one estimate
https://pmc.ncbi.nlm.nih.gov/articles/PMC4345489/ : "Pieces of popcorn contain around 20 mg of water" [1] (cites Hallauer 2001) - CONFIRMED In the conditions of pressure and temperature just before explosion, only a small part (less than 1 mg) is in the vapour phase
https://pmc.ncbi.nlm.nih.gov/articles/PMC4345489/ : verbatim - CONFIRMED Popcorn Board says water "turns into steam" around 212 degrees
https://www.popcorn.org/All-About-Popcorn/What-Makes-Popcorn-Pop : "Around 212 degrees the water turns into steam" - CONFIRMED computed from IAPWS-IF97
https://iapws.org/technical-guidance/release/IF97-Rev.download : Table 34 coefficients match engine.mjs - CONFIRMED tests the steam equation against IF97 check values
https://iapws.org/technical-guidance/release/IF97-Rev.download : Table 35, 300/500/600 K; verifier A passes to 9 figures - CONFIRMED "Mechanism of popcorn popping"
https://api.crossref.org/works/10.1016/S0733-5210(83)80007-1 : Hoseney, Zeleznak, Abdelrahman, J Cereal Sci 1 (1983) 43-52; assay/sources.mjs DOI MISMATCH is a false alarm (excerpt carries no author names) - CONFIRMED in a paper the journal marks as public domain
https://www.cerealsgrains.org/publications/cc/backissues/1992/Documents/69_567.pdf : p. 567 image footnote: "This article is in the public domain and not copyrightable." - CONFIRMED Hoseney et al (1983) reported ... 931 KPa (135 psia) inside the kernel
https://www.cerealsgrains.org/publications/cc/backissues/1992/Documents/69_567.pdf : verbatim, p. 568 (record said p. 567) - CONFIRMED His approach is not completely correct
https://www.cerealsgrains.org/publications/cc/backissues/1992/Documents/69_567.pdf : verbatim, p. 568 - CONFIRMED Byrd and Perona work with "the internal aqueous vapor pressure", a model quantity
https://api.crossref.org/works/10.1094/CC-82-0053 : abstract: a model with a distribution of critical pressures - CONFIRMED hull's strength about 10 megapascals
https://pmc.ncbi.nlm.nih.gov/articles/PMC4345489/ : "ultimate strength σc ∼ 10 MPa" - CONFIRMED "leading to p c ∼ 10 bar"
https://pmc.ncbi.nlm.nih.gov/articles/PMC4345489/ : verbatim - CONFIRMED read the temperature off the steam relation, about 180 °C
https://pmc.ncbi.nlm.nih.gov/articles/PMC4345489/ : "T c ∼ 180°C" via Clausius-Clapeyron - CONFIRMED ACS article quoted in a 2003 classroom handout: 175 °C, 9 atm
https://kicp-workshops.uchicago.edu/eo2014/pdf/popcorn.pdf : "Finally at about 175 ºC, when the pressure inside the kernel is about 9 atm [~132lbs/sq inch]" - CONFIRMED Popcorn Board pairs 135 psi with 347
https://www.popcorn.org/All-About-Popcorn/What-Makes-Popcorn-Pop : "about 347 degrees" (no unit), "135 pounds per square inch" - CONFIRMED Wikipedia pairs it with 180 °C (356 °F)
https://en.wikipedia.org/w/index.php?title=Popcorn&action=raw : live wikitext unchanged - CONFIRMED thermocouples sealed into holes drilled in kernels
https://www.cerealsgrains.org/publications/cc/backissues/1992/Documents/69_567.pdf : "holes were sealed with silicone sealant before popping" - CONFIRMED Wu and Schwartzberg popped 125 kernels one at a time in 200 °C air
https://www.cerealsgrains.org/publications/cc/backissues/1992/Documents/69_567.pdf : 25 per sample x 5 moisture levels, "Each kernel was popped separately", "125 observations" - CONFIRMED Table I temperatures, all 125 kernels 183.5 ± 7.7 °C
https://www.cerealsgrains.org/publications/cc/backissues/1992/Documents/69_567.pdf : Table I p. 570, overall row present - CONFIRMED "most popping occurred between 171 and 177°C"
https://www.cerealsgrains.org/publications/cc/backissues/1992/Documents/69_567.pdf : p. 570 (text layer "1770 C") - CONFIRMED Roshdy 1984 "measured an average temperature of 187°C at the center..."
https://www.cerealsgrains.org/publications/cc/backissues/1992/Documents/69_567.pdf : verbatim, p. 568 - CONFIRMED "only 34% ... 170°C (17 out of 50) ... 96% ... 180°C (48 out of 50)"
https://pmc.ncbi.nlm.nih.gov/articles/PMC4345489/ : verbatim - CONFIRMED "samples with lower moisture content pop at higher temperature."
https://www.cerealsgrains.org/publications/cc/backissues/1992/Documents/69_567.pdf : p. 570, "11.4 16.0% moisture content range" - MINOR Metzger quote, cited as "247, abstract"
https://www.cerealsgrains.org/publications/cc/backissues/1989/Documents/66_247.pdf : text verbatim, but the paper is a NOTE with no abstract; the passage is on p. 248 - CONFIRMED Those are wet-basis percentages
https://www.cerealsgrains.org/publications/cc/backissues/1989/Documents/66_247.pdf : "8, 10, 12, 14, 16, 18, and 20% (wb)" - CONFIRMED Wu and Schwartzberg's table is on a dry basis
https://www.cerealsgrains.org/publications/cc/backissues/1992/Documents/69_567.pdf : "Moisture Content (%, db)"; 14.8/1.148 = 12.89 wet - CONFIRMED "highly correlated (r = 0.826, p = 0.011) with pericarp enthalpy values"
https://eutils.ncbi.nlm.nih.gov/entrez/eutils/efetch.fcgi?db=pubmed&id=15877391&rettype=abstract&retmode=text : verbatim - MINOR pericarp enthalpy is "a measure of how much of the hull's cellulose is crystalline"
https://eutils.ncbi.nlm.nih.gov/entrez/eutils/efetch.fcgi?db=pubmed&id=15877391&rettype=abstract&retmode=text : the abstract attributes a DSC exotherm to cellulose and links it to increased crystallinity; it does not present enthalpy as a crystallinity measure - CONFIRMED filmed at 2,900 frames a second
https://pmc.ncbi.nlm.nih.gov/articles/PMC4345489/ : "Phantom v9 at 2900 frames per second" - CONFIRMED sound before kernel leaves plate; most cracks make no sound
https://pmc.ncbi.nlm.nih.gov/articles/PMC4345489/ : "not caused by the rebound because it occurs before any jump"; fractures "not correlated to any sound" - CONFIRMED "we propose that the familiar 'pop' sound ... release of water vapour."
https://pmc.ncbi.nlm.nih.gov/articles/PMC4345489/ : verbatim - CONFIRMED "approximately 50 ms, without a clear dominant frequency"
https://pmc.ncbi.nlm.nih.gov/articles/PMC4345489/ : verbatim - CONFIRMED "no rocket effect"
https://pmc.ncbi.nlm.nih.gov/articles/PMC4345489/ : verbatim - CONFIRMED a "leg" squashed against the plate that springs back
https://pmc.ncbi.nlm.nih.gov/articles/PMC4345489/ : "'leg' which is compressed on the plate ... This leg bounces" - CONFIRMED "jumps a few millimetres high to several centimetres high"
https://pmc.ncbi.nlm.nih.gov/articles/PMC4345489/ : verbatim - CONFIRMED jump energy about 20 microjoules
https://pmc.ncbi.nlm.nih.gov/articles/PMC4345489/ : "E0 ∼ 20 μJ" - CONFIRMED "two times larger and eight times less dense"
https://pmc.ncbi.nlm.nih.gov/articles/PMC4345489/ : verbatim - CONFIRMED "Effect of moisture content on popcorn popping volume for oil and hot-air popping"
https://www.cerealsgrains.org/publications/cc/backissues/1989/Documents/66_247.pdf : title verbatim; Cereal Chem 66(3) 247-248 - CONFIRMED "Role of the pericarp cellulose matrix as a moisture barrier in microwaveable popcorn"
https://api.crossref.org/works/10.1021/bm049220l : Biomacromolecules 6(3) 1654-1660 (2005) - CONFIRMED (added) none of the sources read reports a direct measurement of pressure inside a kernel
https://arxiv.org/abs/cond-mat/0409424 (and Wu & Schwartzberg, Virot, the Byrd abstract, the Hoseney snippet, five WebSearches) : no direct measurement found; Quinn et al. estimate by theory and gauge only the pot - MINOR (added) "the one study that tried to account for the solids says even that conversion is approximate"
https://www.cerealsgrains.org/publications/cc/backissues/1992/Documents/69_567.pdf : Conclusions give their own estimate, "roughly 110-120 psia and differential pressure across the pericarp is 95-105 psi", below the page's 118-177 range and omitted - CONFIRMED (added) Virot warmed batches of 50 kernels in an oven
https://pmc.ncbi.nlm.nih.gov/articles/PMC4345489/ : "placed in an oven at temperatures increasing by increments of 10°C and lasting 5 min" - CONFIRMED (added) with a microphone beside them
https://pmc.ncbi.nlm.nih.gov/articles/PMC4345489/ : "A microphone Neumann KM 84 (40–16 000 Hz) is added to our experimental set-up." - UNVERIFIABLE (added) Hoseney 1983 abstract (search-engine snippet)
https://www.sciencedirect.com/science/article/abs/pii/S0733521083800071 returned 403 to curl : snippet reads "equivalent to a pressure of 135 psi"; the page already discloses that it was not read - OBSERVED (added) the publisher's site refused our requests
recreated: curl -L https://www.sciencedirect.com/science/article/abs/pii/S0733521083800071 -> 403 : the author saw the same 403 on 2026-10-05 (memory/log.d entry for this session) - CONFIRMED (added) steam-table figures 135.7 psia / 9.23 atm / ~121 psig at 177 °C; 129.4 at 175; 145.4 at 180; 118 at 171; 177 at 188.8; 158 at 183.5; 132 at 175.8; 187 at 191.2; 135 psia at 176.8 °C
https://webbook.nist.gov/chemistry/fluid/ (recomputed with CoolProp HEOS, IAPWS-95, and the iapws IF97 library) : all agree within 0.03 psi; 9 atm = 132.3 psi, 10 bar = 145.0 psi, 347 F = 175 C, 356 F = 180 C - MINOR (added) dek "171 to 189 °C ... 118 to 177 psi"
public/strata/why-does-popcorn-pop/engine.mjs : 177 psia is 188.8 °C; 189 °C gives 178.1 psia - CONFIRMED (added) Wu & Schwartzberg citation, Cereal Chem 69(5) 567-573 (1992)
https://www.cerealsgrains.org/publications/cc/backissues/1992/Documents/69_567.pdf : p. 567 image - CONFIRMED (added) Virot & Ponomarenko J R Soc Interface 12 (2015) 20141247; Byrd & Perona Cereal Chem 82 (2005) 53-59
https://api.crossref.org/works/10.1098/rsif.2014.1247 (and 10.1094/CC-82-0053) : match - CONFIRMED (added) Tandjung correlation is "across a handful of hybrids"
https://pubmed.ncbi.nlm.nih.gov/15877391/ : r = 0.826 with p = 0.011 implies n = 8 - CONFIRMED (added) Metzger: "For one variety"
https://www.cerealsgrains.org/publications/cc/backissues/1989/Documents/66_247.pdf : "One variety of yellow popcorn (A3004) was used in all the popping tests"
What was done
- [fixed] MED, the omitted estimate: re-read in cc69_567.txt (Conclusions, line 1107). The page now quotes Wu & Schwartzberg's own "roughly 110-120 psia and differential pressure across the pericarp is 95-105 psi", says it is below the steam-table figure at every temperature they measured and is a calculation too, and closes the section on three methods giving about 110 to 180 psi and no gauge. Added to the source record as wu-110-120.
- [fixed] Metzger citation now "p. 248", not "abstract".
- [fixed] Tandjung: now "the heat given off by a change in the hull's cellulose that the authors link to crystallisation"; source-record excerpt replaced with the abstract's sentence on cellulose and crystallinity.
- [fixed] Verifier check for the dek's 177 °C was vacuous (the same sentence ends "177 psi"); it now looks for "water at 177 °C", and the 178 probe fails.
- [fixed] Dek now reads "171 to about 189 °C ... 118 to 177 psi" (page, meta, md); the verifier checks the new wording.
- [fixed] Source record wu-equivalent "where" corrected to p. 568.