Question about Bondo...NEED ANSWERS PLEASE

[angib]

Dale,

I would suggest heating the soft stuff up to see if you can kick off the reaction that makes it set, but it sounds like it's quite warm where you are. You could play a hot-air gun over one bit until it's still just touch-bearable - you will then need to leave it alone to cool down before you know if it's worked.

You certainly want to leave it a day before you do anything rash - it may set if left to itself overnight.

As to why, is the second application wafer-thin? It sounds like you're making slow mixes (I'm with vairman, I mix mine so it goes off in 10-15 mins) so they take some time to build up the heat to make the setting reaction happen. If your second application is very thin, it may not be able to generate enough heat to go off (big surface area, but small volume) - though with air temps in the 80s, I doubt it.

Andrew

[cracker39]

I thought about the heat treatment, and if it isn't set up by morning, I'll try it on a couple of small places where I covered screw heads. All of my mixes were getting pretty thick by the time I was finishing up the batch. I had to scrape the final bits off the mixing board with a putty knife as it hardened by the time I got most of it off and onto the wood. None of it stayed soft the whole time.

The first area I tried to sand off has hardened, and I think the heat fromt he sanding did it. Of course, it loaded up the sanding belt and disks badly.

Did you know that in a pinch, the crepe sole on an old shoe will clean up a sanding belt and do a fair job? I have such an old shoe that I'm using to keep my sanding belt clean. I only use the belt sander to partly sand down the long runs on a joint where two pieces meet. Then, it is the orbital to finish of the sanding to a smooth finish.

[mudgepondexpress]

I don't usually add much to the mix but....

Depending on humidity/mix/temp a lot of "mud" ends up with a sticky/rubbery topcoat. The stuff underneath is usually quite hard, but the surface feels soft. The outer layer traps the heat to harden the inner layers, but the outer layer doesn't get the same benefit. I usually keep some cheap sandpaper to scuff off the rubbery stuff before I try to do any shaping, etc. I also like to start sanding before it gets too hard, get the rough shape while it is still generally soft, then finish sand it when it gets hard. It saves a lot of time!

For what it is worth...
Kenny

[Chris C]

Dale,

"Did you know that in a pinch, the crepe sole on an old shoe will clean up a sanding belt and do a fair job? I have such an old shoe that I'm using to keep my sanding belt clean."

Yup! I buy 2x2x12 sticks of gum rubber for just that purpose. It's in all the catalogs. It's really better to buy the sticks, Dale. Saves making you limp when you walk in those shoes.

[cracker39]

I have part of one stick here somewhere. I saw it in a box recently, but didn't get it out and now, can't find the box. So, I just picked up an old mocasin with crepe soles and used it today. I'll find the gum stick sometime when I'm not needing it.

[seahorse]

Doing lots of bodywok over the years, if you increase the amount of hardner your using your cure time will be reduced... Mine usally is ready to sand in 10min., but you have to work fast. Less hardner longer dry times and more working time...


Greg

Like Greg said

[Ira]

Dale, I know this is a stupid question, but:

What are you using the Bondo for right now? Maybe I missed it in one of your other threads.

[cracker39]

Ira, I'm using it as a wood filler. The first application worked beautifully and sanded very smooth...better than any wood filler I've used.

[cracker39]

I guess all's well that ends well. I found what Kenny was talking about. I loaded up a couple of sanding belts and disks getting the rubbery top part off. I think the friction heat helped harden the underlayers, as I was then able to use my orbital with 100 grit to smooth down the rest. I still have a few minor imperfections and think I'll use wood filler to finish these. On the next side, I'll mix the bondo hotter in smaller batches and test a 2nd applicaton on just one small area first.

Thanks for all of the advice, suggestions, and comments.