Rot Doctor

[Miscellaneous Q&A Index]

Subject: CPES vs S-1 (cure chart)

Date: Wednesday, March 18, 2020

Do you have a chart for the S-1 similar to this one for the CPES*?


  Warm Weather Formula Cold Weather Formula
Pot Life At Temperature
86°F/30°C 4 hours NR
68°F/20°C 8 hours 2 hours
50°F/10°C 16 hours 4 hours
32°F/0°C NR 8 hours
Full Cure Time Required
86°F/30°C 2 days NR
68°F/20°C 4 days 2 days
50°F/10°C 8 days 2 days
32°F/0°C NR 4 days
NR = Not Recommended
The different temperature formulations are only applicable during application and for a few days while it is curing.

When will the CPES* be back in stock?



The very short answer is no… on the cure time chart.

The much longer answer is that for all epoxies, the pot life and cure rate is dependent on temperature, and other factors. They are usually rated at room temperature. So a fast setting, 5 minute epoxy (at room temperature) becomes a 2.5 minute epoxy when you go up 10–12 degrees. Or a 10 minute epoxy when you go down in temperature the same amount. And a 20 minute epoxy when you go down another 10–12 degrees.

Then there is the heat that gets added when you mix large batches and keep them together in a lump. In a lump, a large batch of epoxy, or even a small batch, if it is a fast setting formula, will produce enough heat from the chemical reaction to raise the temperature. Which shortens the pot life. Which accelerates the chemical reaction. Which produces even more heat. Under the right conditions, you can get a runaway overheat.

When you add solvents into the mix, you complicate things as well. Solvents keep the epoxy molecules separated, so there is little chance of the runaway heat effect. But it also makes it difficult to make a useful chart. For example, we have taken some of the CPES*, which has the chart you desire, and put a small amount in a liquor shot glass. It took over a month to fully cure. Which is well outside the figures on the chart. The reason for this long period is that the solvents didn’t have a way to gas off quickly. In normal use, however, some of the solvents gas off from the surface, the rest dissipate through the back side of the wood that you are applying it to. So the cure time in normal use is much shorter than the the shot glass example.

To put it a little more succinctly, as a primer on good wood, the cure time is relatively short. Usually 1–2 days. Used to saturate a rotted piece of wood encapsulated in fiberglass, the full cure time could be a month. So making a chart such as the CPES* has really needs to come with a caveat that the chart is only accurate under most conditions.

If you are mainly interested in pot life, rather than cure times, then I would tell you to mix only what you are likely to use in 30–60 minutes. The pot life at any temperature you are likely to work at should be fine then. When you run out, if you still have more work to do, make another batch. It is easy to do so.

There is one other thing that I would like to mention. Given what I have said about temperature affecting pot life and cure time, as you get near to freezing, the pot life and cure time of any epoxy gets longer. If it is a slower setting epoxy, it can be quite long. If you are expecting to work in temperatures around freezing, keep in mind that the cure time gets quite long, and if the temperatures get below freezing for long enough, the epoxy will stop curing.

At this time, it is looking more likely that the CPES* will not be back in stock.

As you have noticed that we are selling S-1 Sealer instead. It is every bit as good as CPES* at strengthening and waterproofing wood, including deteriorated wood, as CPES*. It is a close second in its ability to penetrate, only because it is slower to soak in. So, as long as you keep that in mind, and make sure it saturates what you need it to saturate, you will have excellent results.

There are two other differences worth noting. First, S-1 Sealer doesn’t come in a cold weather version. So it is best used at temperatures between 50 and 95 deg. F. Second, it is significantly cheaper that CPES*.

I hope all this helps. We would be happy to discuss your particular situation via the phone, so that you are using the correct product in the correct manner. Please let us know if we can help further.


* This product is unavailable, we are selling comparable product that will perform these same tasks. Feel free to contact us if you need assistance with which products to use.

[Miscellaneous Q&A Index]

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