Smooth-On resin alert

[Space Garbageman]

Anyone using Smoothcast 300 be advised: Smooth-On's FAQ page suggests using acetone to remove silicone-based release agent from the cast part prior to painting. Go ahead and wipe it on, but DO NOT immerse the casting, it will grow, warp, or otherwise deform, as well as soften and crumble. I just found this out the hard way. Not all of my parts suffered thus, but half anyway, and they were well cured. I'll update this post if the parts dry out and go back to normal. Solvent resistant does not mean solvent proof, clearly. Sheesh!

[USS Atlantis]

I could have told you about the Acetone - it'll also soften Styrene

About the only solvent I let near my Styrene or Resin for cleaning is 90%+ Isopropyl Alcohol

Unless I want to "slurry" some styrene to use in molds or as filler - then I break out the MEK (Methyl-Ethyl-Ketone)

[Spacephrawg]

I interned at a casting studio a few years back and they used that resin in smoothon molds and apparently never needed to use mold release. I don't know if the use of mold release would put less wear on the mold or something but they apparently didnt need it.

[Space Garbageman]

You shouldn't need to use release if you're casting out of silicone rubber molds, but I have been using urethane rubber (Smooth-on's ReoFlex 30). I like the way it pours, and it doesn't need de-gassing. Needs some kind of release, though.

[chasd25]

You shouldn't need to use release if you're casting out of silicone rubber molds, .

True, but it will help extend the mold life if you do use it.

[Space Garbageman]

Just a update: The parts I immersed have continued to warp, almost curling up into a toenail clipping. Not good!

[Maschinen Krueger]

Acetone is used to clean up and remove epoxy paints, glues, so soaking resin parts in acetone would have detrimental results. Because acetone evaporates so fast, just a wipe down should have little affect.

[Space Garbageman]

What about lacquer thinner? Doesn't it contain acetone anyway?

[modelbaseguy]

Lacquer thinner if fine for wiping the resin down but do not submerge. The resin is porous and so it absorbs most anything if immersed long enough. Thinners of various types will attack the binders in the resin and turn them to rubber or cause them to swell and burst. I had some great photos of a kit that I dunked to strip. I left it to soak overnight only to find that it swelled and burst. Ruined the kit but was a cool looking wound effect.

I usually wash my kits down with Dawn dish liquid and warm water to remove the mold release. Works great and does not harm the resin. Using a good primer before painting is always a good idea. I use Krylon automotive primer myself.

[Space Garbageman]

Thanks for the intel. I've been soaking my castings in dish washing machine detergent and water, and using a soft brush. Then I wipe them with lacquer thinner and prime them with a lacquer-based primer like Mr. Surfacer or Tamiya's Surface Primer. So far so good. I figure if I can't easily scrape the primer with my fingernail then the paint will probably stay on.

[chasd25]

I usually wash my kits down with Dawn dish liquid and warm water to remove the mold release. Works great and does not harm the resin. Using a good primer before painting is always a good idea. I use Krylon automotive primer myself.

Worked in a production casting shop years ago, and we used Dawn as well for cleaning mold release off all our parts. Worked great!