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So, I built 30, custom, industrial bases for my new CSM IW army. Really excited about it all. I decide to invest in some casting materials to duplicate them a couple dozen times. Spend all day yesterday getting them prepped for the silicone molding process. Pour about $30 in silicone, and let it cure over night.


Get up this morning, and take the molds apart, and blammo! Uncured molds EVERYWHERE. After some very discouraged inspection, it seems apparent that silicone does not like plastic modeling glue one bit, (Assuming sulfur content) and anywhere silicone touched a bead of plastic glue, it didn't cure.

So, a full day of mold making and $30 down the drain.

The most discouraging part is that I read no less than five articles, watched as many video tutorials, and read all sorts of general molding threads, and no where was it mentioned that plastic glue is reactive with silicone compounds.

I was using Smooth-on 15 BTW.

Thanks for listening. Just needed to get that off my chest.

Im sorry for your loss.

That is all.

I still don't know why hardened glue should react with silicone while being a chemist myself. Would you be so kind as to provide reference to the reaction in question, sulfur components give or take?

 Kosake wrote:
I still don't know why hardened glue should react with silicone while being a chemist myself. Would you be so kind as to provide reference to the reaction in question, sulfur components give or take?

He said in the OP he used poly cement ("plastic modelling glue").

I presume that's what was meant by it anyway.

Yes, I used Testors 3501 Plastic Model Glue Cement.
I'm trying to find reference to it and silicone molding, but nothing so far.

I have never that issue, although i don't use Smooth-on's silicone generally (I found the Oomoo to be iffy quality wise, I like Tap Plastic's platinum cure).

The only thing remotely like it I have seen is that when I use double sided tape to stick small parts inside a moldbox, a tiny bit won't cure where it's in direct contact with the sticky tape surface, but it's not an issue.

If I put together a moldbox in a rush right before a pour, and there is still some CA kicker residue in the creases it won't cure where in contact there either but not a large amount.

Never had any issues using Smoothon with models glued with plastic glue. Did you make sure you cleaned everything properly first? Sorry to hear about the issues but next time I'd do a test pour first, especially if you're new to the whole process. Pouring $30 worth of mold silicon without experience is almost asking for trouble.

I too have made custom industrial bases and used several brands/types of silicone to cast them but my parts were stuck together (for the most part) with crazy glue. I did use testors here and there but I did not cast them up until about a week later. I suspect that I did not have the same issue as yourself as the glue had hardened fully. Testors contains toluene which "is a common solvent, able to dissolve paints, paint thinners, silicone sealants,[12] many chemical reactants, rubber, printing ink, adhesives (glues), lacquers, leather tanners, and disinfectants."

In retrospect after making and casting many of my own, I found that buying aftermarket bases from companies such as Dragonforge Designs and Dark Art Miniatures was more favourable. Although I found that I could cast about double the number of bases for the same cost of purchasing (90 vs 50), I realized that I did not really need so many as I am not building a huge army and I had no intention of going into the base-selling business.

Going back to your situation, I am assuming you also purchased some resin. Your molds still could be useable. I would do a couple of test casts anyway with a small amount of the resin. You may be able to fill in gaps and bad areas using the same bits that you used to build your originals.

Hey all, thanks to those of you who took the time to respond to my whining.
I talked to the guys who sold me my supplies, and I got some pretty solid information from them.

Firstly, plastic cement does cause curing issues if it's not very, VERY set. Mine was about 12 hours old, which is apparently not old enough.

Secondly, they said you can eliminate almost all risk of this sort by priming the model first. He said they use Krylon locally, but that most acrylic primer would do the same. I'm going to try again over the weekend. Thanks for your input.

Good info to know - thanks for the update.

The only issues I've had with glues and silicones is certain RTVs and PVA gllue.

Certain RTV silicone rubbers will instantly BOND to certain PVA adhesives, and you will end up destroying the moulds when you try to separate them.

Since I switched to a platinum cure silicone for resin casting, I've not had any issues, though.

what mould release did you use ..or did you use a mould release


Automatically Appended Next Post:
I have found that the wrong release or no release can result in failed moulds..a good silicone spray release agent ..(not cooking spray or teflon) when making the mould makes a far better mould afterwards you can use a teflon based relase to make castings not the moulds themselves thou

morfydd wrote:
what mould release did you use ..or did you use a mould release


Automatically Appended Next Post:
I have found that the wrong release or no release can result in failed moulds..a good silicone spray release agent ..(not cooking spray or teflon) when making the mould makes a far better mould afterwards you can use a teflon based relase to make castings not the moulds themselves thou

I will second the question. Did you use a mold release? Silicone is OK but we used a spray vaseline release agent which is washable if you ever want to paint the things you are molding.

Did not know that fresh plastic glue causes problems, so that's good to know.

Five minute epoxy also will stick to silicone rubber so make sure to use a mold release if there is epoxy glue on your master.

Tim

you nailed, primer was the issue...