We are looking for a filler for maple mitered frames to fill small seams in miters prior to finishing with pre cat primers and top coats with both solvent and waterborne. The key issue is the frames are cured in a PrimeHeat batch tunnel and the miter is sometimes sinking slightly. We think we need a putty that will stretch when going through the heat. Any help would be appreciated.

have you tried nitrostan glazing putty?

I have been using 3M Acryl-White Glazing Putty. It fills nicely, you can get it in white, green, red, etc. Dries fast and i've not noticed much in the way of shrinkage.

Bondo is a polyester resin based filler. It would be the worst choice. It takes a very long time to cure under normal conditions and shrinks considerably. Often people will apply it, wait a few hours for it to harden, sand it, and paint it. It then continues to shrink over the next week, which leads to telegraphing thru the finish. The only way to repair it is another coat of a stable filler and a repaint.

Bondo is a great product for fixing many things. We often get away with it when burying it with house paint. In the shop it works okay if a lump of its left to cure for a few days and then buried under plenty of primer.

I would expect your heating process to shrink the bondo very fast. Its brittle and will crack in the miter.

I would likewise try the 3m Acryl marine putty. It fills much larger defects than nitrostan(pin holes). Its often used on wooden boats which move around. It has almost zero shrinkage due to its high flash off solvent base.

Which glue are you using in the miters? Anything other than a TB1 glue will shrink.

Thanks for your help. I will be trying these products.
I do have one question for Adam:
What is TB1? Is this a product or a type of
putty?

its glue. TiteBond1

Leslie,

Please post a closeup pic of the problem. Describe the glue and reinforcing of the miter.

I have found that whatever vehicle of solvent I am using for topcoat we use the opposite for filler. Which for us means solvent based finishes and waterbased fillers. Otherwise we get the smallest of reactions if we use the same as you are basically softening the putty and get some telegraphing. For us Elmers interior is the go to putty we use and it is widely available.

ProH20 water based putty isn't easy to find, but I have found it to be the most useful putty in the shop. It also doesn't shrink much.

Timbermate makes a product very similar that we use if I can't find the ProH20. For some reason the ProH20 seems to hop from vendor to vendor in the quart can sizes. One week I can get it, the other, I can't.

Durham Rock Hard Putty is a water based putty that can be tinted with any water soluble tint. It comes in powder form and it has a good holdout on small type dents as well as gaping gaps. It wont shrink or crack. Sands real nice when dry and can be bought at a Hardware Store for a reasonable price. I highly recommend it.

I 2nd the ProH20 Great product. I get it from Baer.