Estimates years remaining until vinegar syndrome onset (D reaches 0.5%) from your cel's current AD strip reading, structural damage state (D), age, and storage environment — compared against a textbook Arrhenius benchmark.
Sets Pint directly (Table 3 PPM band) and gives a floor estimate for D via titratable acidity.
An A-D level is not a diagnosis of vinegar syndrome. The strip reads acetic acid in the air around the cel right now. VS onset in this framework is defined by structural damage — D reaching 0.5% — which is what the estimate is built on. The two usually move together, but not always: a high reading with low measured D means the acid is coming from somewhere other than this cel, and the fix is the enclosure, not the artwork.
How you test decides what the reading means. Sealed alone with one cel, it reflects that cel. Left in a binder or box with others, it reflects the whole enclosure.
Used to estimate D via the 0.01%/yr baseline clock (70°F/40%RH IPI reference) if you don't have a measured value. That clock is linear — it is IPI's own assumption that the rate never changes — so it is a neutral prior about storage you cannot see, not a framework result.
A lab-measured deacetylation value, if you have one. It overrides the age and A-D estimates entirely and anchors the result at today, since a measured D already accounts for the aging so far.
No lab result? Use the handbook's baseline clock: 0.01%/yr under general storage, so D ≈ 0.01% × the cel's age. Leave this field on “Unknown” and the tool applies that clock for you.
Pristine-cel benchmark: R = R0(T) · aw — Arrhenius in temperature, times a first-order water-activity term, because deacetylation is a hydrolysis and needs moisture to proceed. Strict Arrhenius is temperature only; the RH factor sits alongside it, not inside it. D=0, Pint=0, no autocatalytic feedback. This is the "textbook" number, calibrated to reproduce the IPI's 50-year guideline exactly at the framework reference condition of 70°F/40%RH.
Applies the framework's relative penalty — (1 + κ·D)·(1 + Φ·Pint) — to the Arrhenius benchmark. It depends only on this cel's state (damage D and vapor Pint), not on the environment, which cancels. A pristine cel has penalty ×1.00, so at the reference (70°F/40%) Cel Nexus equals IPI Baseline exactly.
Depends only on the measured D and Pint state — not on temperature or RH, which cancel in the ratio. Environmental sensitivity is carried by the Arrhenius benchmark, so the same state gives the same penalty at any T/RH.
Two readings of the same cel, both counted from today. IPI Baseline knows only the calendar — it assumes reference-rate aging since production. Cel Nexus starts from the cel's measured state. Where they disagree is the useful part: if the state-aware figure is the higher one, this cel has aged more slowly than its years suggest.
Predicted onset window — this cel
IPI Baseline (benchmark). Arrhenius supplies the temperature dependence only; the water-activity factor aw = RH/100 is a separate first-order moisture term, since deacetylation is hydrolytic. A pristine cel's rate is R = R0(T) · aw with onset at D = 0.5%. R0 = 0.025 %/yr is the Intrinsic Thermal Velocity at the framework reference of 70°F / 40% RH (aw = 0.40): 0.025 × 0.40 = 0.010 %/yr → 0.5 / 0.010 = 50 yrs, reproducing the IPI 50-year guideline exactly. Temperature scales R0 by the Arrhenius factor exp[(−Ea/R)(1/T − 1/T_ref)].
Cel Nexus (relative penalty, Eq. 16). Comparing a degraded cel to the same cel pristine, the environmental terms (β, R0, aw) cancel, leaving a dimensionless state penalty: Relative Penalty = (1 + κ·D) · (1 + Φ·Pint). This cel's effective lifetime = Arrhenius lifetime ÷ penalty. Pristine (D=0, Pint=0) → ×1.00, so Cel Nexus equals IPI Baseline at the reference. The penalty depends only on the cel's state — accumulated damage D and internal vapor Pint — not on storage geometry or scavengers.
Scope: pre-autocatalytic only. Everything here models the induction phase, D < 0.5%. At or past the 0.5% brink the tool reports “at/past onset” rather than projecting a date, because post-brink degradation follows a different rate law. Ea = 105 kJ/mol (IPI/Adelstein induction-phase fit) sets the benchmark's temperature sensitivity; κ = 2.0 standard / 1.0 low / 4.0 heavy-paint; Φ = 0.5 PPM⁻¹.
Strip level vs. damage state. Pint (from the strip) and D are different quantities: Pint is free acid present in the enclosure now and is reversible — ventilate or scavenge and it falls. D is accumulated deacetylation and is not. That is why a high strip level on a cel with low measured D still returns healthy remaining life: the model treats the acid as an accelerant acting on the material, not as the damage itself. Onset is defined at D = 0.5%, never at a strip level.
Why the two cards diverge on the same cel. The age clock is linear at 0.01%/yr, which is IPI's assumption that the rate is constant for life. The framework's rate law is not constant: R = R0·aw·(1 + κD) rises as damage accumulates. The two agree exactly at D = 0 and separate from there. Seeding D from the linear clock is deliberate — it is the neutral prior for a cel whose storage history you do not know — and the gap between the cards is the framework's actual claim: once D is high, IPI's constant-rate figure is optimistic.
D is estimated as the larger of: (a) age × 0.01%/yr baseline clock, or (b) the AD strip's titratable-acidity band — unless you supply a measured value directly. Pint comes straight from the AD strip's PPM band (Table 3).