nathan wrote:Well, I gave the process a test. I used it on some model kit sprue I had because they had some really fine pressure pin lines and I wanted to see if it would pick them up. I tried the method above (straight silicone for the first layer) but I didn't like the process. It was a major pain to work with.
So I tried the tinned method. Much better. But too slow to cure. The post on that Myheap site said that using glycerin or paint with the thinner would make it lumpy and that it was counter productive. But I tried it anyway. I thinned down some silicone caulk with some camp fuel (naphtha white gas) and added glycerin and paint. It didn't turn lumpy at all. I painted it on (and it went on easily when thinned) and set the sprue chunk aside. It cured fast and normally. It didn't lump up or shrink or anything. Naphtha as a thinner and glycerin and paint as a catalyst work together just fine.
Cool! more tools for the toolbox, and another confirmation of technique. How much did you thin it? What were your proportions?
I found that diluting it with Mineral Spirits much would result in the mold curling up if the mold was thin in cross-section.
nathan wrote:My friend has some plaster blocks in which he carved a stone pattern that we wants to test it on, so I'm going to do that Saturday. Plaster is pretty porous, so I'm going to have to do some reading on how to properly seal it.
Watered down white glue/Elmers (PVA glue for the Brits out there) or shellac should do the trick.
nathan wrote:Oh, and the silicone replicated the detail just fine. It even picked up some pin indents that I couldn't see with my naked eye. I saw them when I looked through a magnifying lense and thought something was wrong with the mould and then grabbed the sprue and saw them on the sprue itself.
nathan wrote:I've always not bothered doing much more than the occasional conversion because I thought replicating what I made wouldn't be economical. But now... now there's scratch building to be done.