Welcome to the BrickWood forums, and sorry for the circumstances.
Are you saying this happened during your curing fires? Or by heat are you talking about the ambient temperature where you are?
If this is the silicone adhesive that comes with the Duratech kit, it’s rated for 500°F+ steady and shorter periods at 600°F. If you have not yet had a fire in your oven, or even if it was a curing fire, I don’t think it would be the heat.
The adhesive has an acetic acid (vinegar) component that cures the silicone by exposure to atmospheric moisture. Once it is fully cured it should have a consistency similar to rubber.
Is the adhesive that was left behind an elastic, or is it more rigid and brittle? I’m guessing that it’s the latter from what you’re describing.
If mechanical methods (scraping/prying with a putty knife) do not work, I’m not sure what else will. You may have to keep peeling.
Two suggestions for replacing the cap base when you get there:
- Get a fresh tube of the silicone adhesive (high heat like the original). The manufacturer recommends that it be used within 18 months of packaging—and I’m hoping you did not get a tube of old product. When you apply the adhesive, use plenty of it, bring it up over the edges of the base plate, and seal it over the edges.
- There are holes at the four corners of the base plate. Use four Tap-Con screws and anchors to fasten it mechanically at the four corners. In most cases the adhesive should be enough, but you want to be really sure this time that your plate is fastened, and that it stays fastened.
Again, I’m sorry to hear you had an issue, and I hope these suggestions are helpful. Please let us know how it all turns out!
PS: There are a lot of builders who don’t get this done in the minimum time frame—you’re in good company!