robalo01 Posted July 16, 2014 Report Share Posted July 16, 2014 Hi, I have made quite a few bondo molds for lead pouring in my days and they work, but they don't last very long. Is there anything that could be added to it to make it more heat resistant? Silica sand, iron oxide, etc? Is POP or Durams Water Putty more heat resistant than bondo? Stephen Quote Link to comment Share on other sites More sharing options...
Anglinarcher Posted July 16, 2014 Report Share Posted July 16, 2014 I don't think that Bondo can be made heat proof. Adding Silica might help, but the Bondo itself is the problem. The chemical bonds break down when it gets hot. POP initially is very poor with heat, but if you bake it to remove water, or let it cure for weeks in a warm place, then it handles heat better...... but it is not real strong. POP is cheap, not strong. Water Putty, sorry, never tried it so hopefully someone else can chime in here. HELP all you experienced guys? Quote Link to comment Share on other sites More sharing options...
jcool3 Posted July 17, 2014 Report Share Posted July 17, 2014 Problem with my bondo molds is that they eventually warp and start leaking lead. Switched to rtv silicone molds, more expensive, but way easier to work with and better results. Quote Link to comment Share on other sites More sharing options...
robalo01 Posted July 18, 2014 Author Report Share Posted July 18, 2014 I've never used silicon molds for lead before. 1. Where do you buy your silicon? 2. About how many castings do you get out of a silicon mold? Say a 1/2 jig mold. using 75ml of silicon. Stephen Quote Link to comment Share on other sites More sharing options...
Vodkaman Posted July 18, 2014 Report Share Posted July 18, 2014 I know about the warping problem as the mold gets hot, from when I was developing a ballast pouring system. The solution that was suggested to me by Sagacious, here on Here is a write-up I did on the subject. I could not find the original Sagacious thread. Dave Quote Link to comment Share on other sites More sharing options...
jcool3 Posted July 23, 2014 Report Share Posted July 23, 2014 I've never used silicon molds for lead before. 1. Where do you buy your silicon? 2. About how many castings do you get out of a silicon mold? Say a 1/2 jig mold. using 75ml of silicon. Stephen google gt products gt-1350 for someone that will ship to mexico you can find it on ebay. dont know how many castings, as I never poured more than a few dozen jigs per mold. Quote Link to comment Share on other sites More sharing options...
scrubs Posted July 28, 2014 Report Share Posted July 28, 2014 I've used Durham's Water Putty for molds where I wasn't pouring too many castings. A lot stronger than Plaster of Paris. Just make sure it's VERY dry before your first pours. bill Quote Link to comment Share on other sites More sharing options...
robalo01 Posted July 29, 2014 Author Report Share Posted July 29, 2014 Anybody ever used investment casting slurry? I am going to pick some up this afternoon. Quote Link to comment Share on other sites More sharing options...
Rustyfawcett Posted July 13, 2017 Report Share Posted July 13, 2017 I know this is also a older post but don't know about heat proofing the bondo but for the warping you can add small metal rods the length of the mold inside the bond .also adding fiberglass strands to the mixture after the first coat over the master will also help. we had the same problem making metal castings for model train parts and we found that it helped Quote Link to comment Share on other sites More sharing options...
