Building a Hot Box

[pintopete]

I’m planning on building a hot box for the curing of stock finishes. I was thinking of using foil faced rigid urethane foam board with a removable top from which the stock would be hung. I could use a light bulb as a heat source in a porcelain socket. It won’t take much heat inside the foam box though. I also thought of building in a small computer fan to circulate the hot air.

Any ideas or suggestions? What temperature seems appropriate?

Thanks, Peter.

 

[Dusty Stevens]

I’m planning on building a hot box for the curing of stock finishes. I was thinking of using foil faced rigid urethane foam board with a removable top from which the stock would be hung. I could use a light bulb as a heat source in a porcelain socket. It won’t take much heat inside the foam box though. I also thought of building in a small computer fan to circulate the hot air.

Any ideas or suggestions? What temperature seems appropriate?

Thanks, Peter.

120deg is what cures car paint

 

[DaveTooley]

I wouldn't worry about a fan. It will cause to many problems. Put your heat source in the bottom.

 

[Twdmar]

I have done several bows and one gun stock finish in a hot box. Make it bigger than you think by a bit. Use thicker foam and stick it on a wood base. Reinforce the corners or make the whole thing out of wood and line with rigid foam.
I wired in several lights and put incandescent lights in the lid but you could do them in bottom too but you'll need a wider base so the lights are not so close to your parts.
I could get 180-200 fahrenheit for curing epoxy by throwing a blanket over the top. I used 1/2" foam, if i do it again, I'd do thicker. You can get a rheostat that will shut it off once you get it to temp so it doesn't get too hot but I just left a small gap at the lid to adjust the temp.
A kitchen thermometer with a probe can be jammed in through the side. You won't need the fan if you use a few lights. I did park a smoke detector nearby when i used it inside but it was never an issue.
One final thing, make sure you finish has flashed off the solvent before you cook it. It you heat it too soon the other layer can harden and the solvent trapped underneath can cause problems.

 

[Alex Wheeler]

We bake them up to 140 degrees. But not wood. Unless you like a million air bubbles.

 

[pintopete]

All great ideas and suggestions. I may start at a low temp such as the 120* suggested by Dusty. Can always go hotter if that is too low. Thank you.

 

[pintopete]

Back to this project. Rainy Saturday. Measured a couple stocks on hand. Need a minimum of 7”depth, x 33” length. Width doesn’t matter so much because I plan the box to be square. Down to the basement to check on leftover building materials on hand; rigid foil faced foam board. Found that I have 1” thickness 7’ + long, and some pieces. After evaluating what I have, and quick planning, my external dimensions will be 42-1/4” x 16” x 14”. That nets an interior of 14” x 12” x less than 42-1/4”. Right out of the gate, I feel what I will end up with will be on the small side ideally, but will likely work. Being a scrounger, this is what I’m going with. I can’t find Gorilla glue in my scatter, so a trip out will be necessary. I’ll keep you posted…

 

[stavey]

I use a digital smoker for cerakote . Works perfect.

 

[tobnpr]

Company I buy rust blueing solution from suggests a U-Haul cardboard wardrobe box- cheap and big enough, plus you don't need to "build" anything.

 

[pintopete]

Company I buy rust blueing solution from suggests a U-Haul cardboard wardrobe box- cheap and big enough, plus you don't need to "build" anything.

I like that garment box idea. Especially if the need for a hot box is infrequent. Thanks!

 

[tobnpr]

^^^
Yep. Just fold it back up and put it away when not needed.

 

[pintopete]

Enough for today.

 

[pintopete]

Well, hot box is finished. If anyone wants to build something similar, I have some suggestions learned while constructing mine. First is that if you only need it for one or two stocks, use the garment box idea that @tobnpr suggested. Very smart, and cost effective. Plus you can always fold it up, recycle it, or use the cardboard box for something else.

If you want something more permanent like mine, anticipate storage when not in use, and I would suggest a larger size than mine. I used scrap foam board that I had in the basement. If building new, buy a 4x8’ sheet, and make the box 16x16x48”. That way you can more comfortably fit stocks that are longer.

In my hot box, so far I have used an old 40W GE tubular bulb that I found in my collection. It will heat the box to 95-100*. That has been hot enough for my purposes. The tubular bulb created more heat than a conventional bulb of the same wattage in my experience. I did not try a 60W bulb, but I’m sure that would create at least 120*.

I’m looking forward to finishing a couple stocks, and go shooting!

Peter.

 

[pintopete]

Views of top & unfinished bottom. Use a hex box for mounting the ceramic bulb base to the plywood. Not pictured here.