Vessel pressure
Model trapped-air heating and CO2 pressure in a fixed headspace.
Pressure landscape
Temperature × free headspace · every cell calculated independently
What drives the estimate?
+10% free gas space ⇒ -5.98 PSI gauge difference
+10°C at fixed conversion ⇒ 2.19 PSI gauge difference
Exact model recalculations, not uncertainty intervals or safety margins.Equation
Not a worst-case estimate: evaporation, changing volume, partial CO2 dissolution, thermal gradients, leakage, and vessel mechanics can shift the actual pressure in either direction. Do not use this calculation to certify or select a sealed vessel.
Calculation method Equation, inputs and limitations
How vessel pressure is modeled
Two contributions are summed. First, the trapped air sealed inside the vessel at room temperature is heated to process temperature — ideal-gas law gives its new absolute pressure. Second, CO2 produced by the THCa → THC + CO2 reaction occupies the headspace volume at process temperature, contributing an additional partial pressure.
Gauge pressure is total absolute pressure minus the reference ambient pressure. Model assumptions are now editable: sealing temperature (70°F default), initial sealing/ambient absolute pressure (1 atm default), and the fraction of THCa converted (100% default). The entered volume is the free gas headspace at the modeled conditions, not the nominal vessel size. The pressure landscape evaluates a centered ±30 K temperature sweep at seven headspace-volume multipliers, with exact values recalculated for each cell.
The model assumes a constant, rigid free-gas volume and a dry ideal gas mixture. Vapor pressure, material displacement, changing headspace, gas dissolution, vents or leaks, wall compliance, other released volatiles, non-ideal phases, and unequal gas and sample temperatures are omitted. The calculation is neither a guaranteed upper bound nor evidence that a sealed vessel is safe at any predicted pressure; relative heat-map coloration never represents a safety threshold.
Mean molar masses: THCa = 358.47 g/mol; CO2 ≈ 44.01 g/mol. Molar gas constant R = 8.314462618 J/(mol·K). Reference values: PubChem CID 98523 and 280, NIST CODATA. Gas pressure follows nRT/V.
Questions & limitations 3 answers
Does the pressure result include solvent or terpene vapor?
No. The model adds the pressure from heated trapped air and CO2 released by THCa. It omits vapor pressure, material displacement and changing gas volume, so the number is not a guaranteed maximum.
Why are gauge and absolute pressure different?
Absolute pressure is referenced to vacuum. Gauge pressure subtracts the assumed surrounding atmospheric pressure. The same gas state can therefore have two different numerical pressure readings.
Can a jar be considered safe because the predicted pressure is low?
No. The equation does not evaluate glass strength, closures, temperature gradients or failure modes. Ordinary jars are not pressure-rated processing equipment.