Hey all, long time lurker but first time poster. I've recently gotten into silicone mold making and resin casting (thanks in part to a lot of good advice I've found on these boards). However, I've run into a resin casting issue I've been unable to find any guidance for on my own.
I'm aware of some resin issues resulting from improper mixing ratios, and even experienced a bit of that as a result of early trial and error. The issue I'm getting seems different from what I've read about. Basically what seems to be happening is, on only a few casts, I find that the resin on the outer surface of the mold seems to have fully cured, but the material on the inside at certain spots on the cast is still soft, to the point the outer surface is flexible and can crack with enough pressure. If I leave these casts along for a few days, the inner material does seem to harden eventually. The issue is, when I try to paint these casts, air bubbles will form under the paint after a day or so.
I'm using a mold made out of Mold Star 15, and my resin is Smooth Cast 300. I've been tinting the resin to a light-medium gray using Uvo Black pigment. I've been doing my best to be accurate with the mixing ratio for the resin (using the same mixing container which I've marked to help me pour out the correct levels, cleaning it between each cast) and following all relevant instructions. I have noticed that the leftover material in the mixing cup will sometime exhibit a similar behavior, with the surface exposed to the air hardening and everything below remain hard.
Right now the only thing that my gut is leaning towards is the pigment. I've made a few casts where the resin is not tinted and never seen this issue, but it's only a handful of attempts and there are quite a few times where casts with the pigment have turned out okay.
Thank you for any advice you can give.
I'm aware of some resin issues resulting from improper mixing ratios, and even experienced a bit of that as a result of early trial and error. The issue I'm getting seems different from what I've read about. Basically what seems to be happening is, on only a few casts, I find that the resin on the outer surface of the mold seems to have fully cured, but the material on the inside at certain spots on the cast is still soft, to the point the outer surface is flexible and can crack with enough pressure. If I leave these casts along for a few days, the inner material does seem to harden eventually. The issue is, when I try to paint these casts, air bubbles will form under the paint after a day or so.
I'm using a mold made out of Mold Star 15, and my resin is Smooth Cast 300. I've been tinting the resin to a light-medium gray using Uvo Black pigment. I've been doing my best to be accurate with the mixing ratio for the resin (using the same mixing container which I've marked to help me pour out the correct levels, cleaning it between each cast) and following all relevant instructions. I have noticed that the leftover material in the mixing cup will sometime exhibit a similar behavior, with the surface exposed to the air hardening and everything below remain hard.
Right now the only thing that my gut is leaning towards is the pigment. I've made a few casts where the resin is not tinted and never seen this issue, but it's only a handful of attempts and there are quite a few times where casts with the pigment have turned out okay.
Thank you for any advice you can give.