Starship Modeler Discussion Forums

Space Garbageman · Joined: 25 May 2008 Posts: 52 Location: Portland OR, USA

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 · Posted: Fri Oct 09, 2009 7:57 pm Post subject:

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)
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Spacephrawg · Joined: 24 May 2006 Posts: 989 Location: Newton, MA

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.
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Space Garbageman · Joined: 25 May 2008 Posts: 52 Location: Portland OR, USA

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 · Joined: 15 Jul 2002 Posts: 283 Location: SF Bay Area

Space Garbageman · Joined: 25 May 2008 Posts: 52 Location: Portland OR, USA

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

Maschinen Krueger · Joined: 13 May 2003 Posts: 527 Location: Colorado

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.
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Space Garbageman · Joined: 25 May 2008 Posts: 52 Location: Portland OR, USA

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

modelbaseguy · Joined: 24 Sep 2002 Posts: 318 Location: charlotte, nc

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.
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Space Garbageman · Joined: 25 May 2008 Posts: 52 Location: Portland OR, USA

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 · Joined: 15 Jul 2002 Posts: 283 Location: SF Bay Area