Replies

1. 
   joeleonetti | Aug 08, 2023 02:04pm | #1

   You might want to call the Bondo company and ask them. Their technical folks will likely have an idea.

2. 
   _mj_ | Aug 08, 2023 04:02pm | #2

   See if you can find a slow-cure product. My first car was a 1974 Ventura where soft spots had to be chopped out where it just NEVER hardened up. Too much will make it set up fast, too little is dicey. I still don't know if it was short on hardener or I did a bad job mixing it. Odd things can get stuck in your head...

3. 
   john_c2 | Aug 08, 2023 06:01pm | #3

   Yeah, it really needs to be mixed at the correct ratio. Less hardener is not going to get the results you want. The only alternatives I've used is a slow curing epoxy mixed with the proper filler to get the kind of results it seems you're looking for.

1. 
   [email protected] | Aug 09, 2023 11:01am | #4

   Agreed, there are no short cuts to quality work.
   There are plenty of slow curing products available.

4. 
   pantalones868 | Aug 09, 2023 02:58pm | #5

   I'm a woodworker so consequently I have had a lot of old cars and live by the beach so a lot of rust to go with them. I have way more experience with bondo than I ever would have wanted. There is no " slow" with bondo but it is fairly forgiving as to ratios to hardener. Too much hardener and it goes off faster than you can use it. In use, you take a dollop of bondo and a squeeze of hardener and experience using it tells you what is correct , it's not very scientific. You can reduce the set up time by reducing hardener. When your mix is red it's probably too much hardener,too fast, for practical use. A solid salmon color is probably ideal but is still sometimes to fast for a larger area. You can reduce the hardener to a pale pink and it will still set up but give you a little more time, and its just a little. In mixing, each time you mix always use a clean,unused container . Even when you clean out the container,like the lid that comes with it for mixing, somehow the set up time is faster if it had been used for mixing before. I don't know why that is but it seems to be the case.
   I know bondo is widely used for wood situations, painters use it all the time for repair work, as have I, but in truth bondo really sucks for wood applications. Its sets too hard and expansion and contraction of the wood eventually leads to compression and likely failure eventually.

5. 
   eddo234 | Aug 09, 2023 03:56pm | #6

   Since this is a woodworking forum, can we assume your project involves wood? As others have said, don't do it. There are many slow cure epoxies out there, perfect for woodworking. I've always used West System (but there are lots of brands to choose from), their 206 slow hardener has a 90-110 minute working time at 72 degrees!

6. 
   mitch912 | Aug 11, 2023 07:57pm | #7

   One point that never seems to be mentioned is that the hardener is benzoyl peroxide. This is an oxidizer and can cause skin sensitization.

   It also bleaches fabrics, including carpets. It only requires a very small amount to cause bleaching on nylon. Gloves, and be careful where you get it.