Naphtha and RTV molds Nov 4, 2010 23:24:43 GMT 1
Post by rasputen on Nov 4, 2010 23:24:43 GMT 1
I tried searching for more information on using Naphtha in RTV molds but the search tool doesn't seem to be able to come up with anything. When I add high percentages of Naphtha, like 80% - 110%, I find that my RTV molds want to curl up a fair amount as they cure. It is almost as if the top of the pour is not shrinking as much as the bottom of the pour, which seems backwards from what I would have expected. I have noticed too that the curing time for the RTV can be more like three hours instead of the advertised 75 minutes - I'm not sure if this symptom is related or not. I am using OOMOO 25 tin-curing RTV from Smooth-On, which is the fastest curing time I could find here in the US. I think I can still make a casting from the molds by weighting down each corner of the mold when I pour the resin in, but I was hoping to be able to make several castings from my Naphtha/RTV mold which will not be easy. The molds have been sitting for about a week, and the dimensions of the vehicle seem to be correct. I also tried making the mold in a larger box, leaving more rubber around the sides of the pattern, but this didn't help. Is there any way to prevent the molds from curling up as they shrink?