Duratech Cap Fell Off

Hi,
First post. First off, Kudos to those who are able to finish their ovens quickly. I’ve been working since May and still haven’t finished

However I recently bumped the Duratech Cap lightly and it fell off. Furthermore it looks like the glue on the inside was either not fully cured or that it melted due to the heat. I used the glue that came with the kit and followed the directions for gluing the vent cap. Note that I started peeling away the glue in the below pic.
image

Has anyone ever seen this?
Is there a easy way to get that glue off the brick?

Thanks for the help.

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:

  1. 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.
  2. 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!

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Thanks for the reply.
The oven has gone through the curing process and about half a dozen cooking fires. I put in three layers of insulation and can get the dome up to approx 900 degrees according to Mr. IR Thermometer.

As far as your question about the glue: Looking at the picture on the top and right, the glue nearest the chimney hole is elastic and sticky, kind of like chewed gum. The part where you see the brick was rubbery and peeled off with a putty knife and some moderate effort. The bottom of the flange had no glue stuck to it, just a thin layer of white somewhat greasy residue.

To get the glue off I used a putty knife and a small wire brush in my drill. This cleaned up the glue, roughed up the brick a little but required a very light touch on the mortar joints.

To re-attach the flange I decided to overkill. I used JB Weld Extreme Heat metal glue. It is advertised to survive 2400 degrees. I first tested on a spare fire brick to make sure it would bond and not damage the bricks. After a successful trial I glued the flange back on and it is currently curing.

Good hint about the tap cons. I’ll do that and test fire the oven this weekend and post the results.

Here is a pic of the progress so far:

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That sounds like the adhesive didn’t cure properly, or even separated. (Thinking of the white greasy residue.) I’m glad you were able to remove all of it.

After a little research, I’m a bit concerned. Extreme Heat is an epoxy designed for metal repairs (like holes and cracks), not an adhesive. I know that JB Weld mentions outdoor grills and fireplaces, but I think that refers to sheet metal and iron components like heat exchangers. It will cure as a rigid mass rather than a flexible seal, like the silicone was intended to do.

I definitely understand your skepticism about trying silicone adhesive again, when the result the first time looked like neither silicone nor adhesive. I’m also, again, concerned that JB Weld introduces its own set of problems.

See how it works for you; let us know. Tapcons might be even more important here.

Best of luck!

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You bring up a very good point which I did not consider when I did it. I had one fire this weekend before the rain set in with no ill effects. However it was a small fire just for cooking burgers.
I have reached out to the brick manufacturer to see what the coefficient of thermal expansion is for their bricks. I’m guessing the repeated thermal cycling will eventually strain the joint enough to cause the glue (or bricks) to crack, though the smaller the difference in expansion the less critical it’ll be.
I’ll post when I know more.

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Thanks for keeping us posted on this. It’s the kind of question that may help others down the road, and I appreciate it.

Wow…love the curved wood Pergola? I wanted to do curved…but just couldn’t add to my workload. How did you curve such thick wood?

Dwayne

Thanks. I really like it but it’s a lot of work.

The pergola beams (qty 2) are actually three layers of 1/2" pressure treated plywood. I built a form using 2x4s on top of the curved cabinet structure using the two 4x4s as the basis to make sure the curve was correct. I then used construction glue and every clamp I owned plus some more that I bought to bend the plywood around the forms. Then I used screws, mainly on the inside where you can’t seen them, to add additional strength. I would have loved to laminate solid wood but I couldn’t find any 3/4" or 1/2" thick 8" wide pressure treated and I don’t have a planer.

When I removed the clamps the beams relaxed a bit. I secured one side of the beams to one of the 4x4s, dry fit the rafters to make the curve consistent and then used some clamps to get the beam in the exact position on the other 4x4, then more screws.

-K