Epoxy pour temperature and timing helper

What this helper does, and what it refuses to do

Data sheets print times such as pot life, working time, time between pours, demold time and full cure. Each one was measured under stated conditions: a temperature, and often a mass or thickness of mixed resin. Gougeon Brothers, for example, bases its WEST SYSTEM cure times on 72 °F and notes that the epoxy cures faster when it is warmer (Epoxyworks).

The helper does two things with that data:

1. It compares your shop temperature with the temperature range the manufacturer publishes, and says whether you are inside, below or above it.
2. It lists every published time for the product with its conditions, and, if you enter the time you mix, turns each one into a clock time.

It does not stretch or shrink the times for your temperature. There is no single rule that holds across products, and a number we invented would look as authoritative as the manufacturer’s. When your shop is outside the published range, the helper shows what the manufacturer says to do instead, with a link to where it says it.

Formula and assumptions

clock time of a stage = mixing time + published time

• A published range (for example 24 to 72 hours) becomes a window with a start and an end.
• Pot life is usually measured on a small mass in a cup. Resin spread thin on a surface stays workable longer; resin left in a bucket gets hot and sets sooner. West System notes that a larger or thicker mass generates more heat (West System).
• Your temperature is compared with the published bounds exactly; the range is never widened. When a data sheet prints a range in both °F and °C and the two do not convert exactly (data sheets round when they convert), the helper says so and checks the unit the value was recorded in.
• If a product publishes no temperature range, the helper says so and does not check.

Worked example

A deep-pour product publishes a working time of 4 to 6 hours, at least 36 hours between pours, a demold time of 48 to 72 hours and full cure in 5 to 7 days, with a recommended application range of 60 to 80 °F. Your shop is at 68 °F and you mix at 9:00 on Saturday. These figures are for illustration; choose a product in the helper to use its data.

1. Temperature: 68 °F is inside 60 to 80 °F.
2. Working time ends between 13:00 and 15:00 on Saturday.
3. The next pour can start from 21:00 on Sunday (36 hours).
4. Demold between 09:00 Monday and 09:00 Tuesday.
5. Full cure between the following Thursday and Saturday.

Using the result

• Below the range: warm the space, the resin and the surface before mixing, as the manufacturer directs. The cold and warm shops guide collects what manufacturers publish about this.
• Above the range: expect shorter working time and more heat in thick pours. For warm conditions Gougeon Brothers suggests mixing batches you can use within about half the pot life and spreading the resin out of the mixing pot quickly (Epoxyworks).
• Layered pours: use the time between pours with the layer planner to see the whole schedule.