Lily
10-06-2015, 08:53 PM
I wanted to gather together a master list of "known offenders" that cause silicone to cure very slowly or not at all. Most of this has been discussed again and again, but I've found some through trial and error that I'd never heard of. (Note: When I say "paint," I mean mixing together silicone, pigment, and thinner to paint the tail with an airbrush. Not just slapping actual paint on the tail!)
Latex
A type of rubber found most commonly in gloves and sometimes used to make molds. NEVER use latex gloves when working with silicone. Don't even have it in the same room. Even the residue on your hands or anything you've touched can cause silicone to get angry and refuse to cure. Latex molds are completely out the question, as your silicone will never cure in a latex mold.
Nitrile
Another type of rubber glove. Not nearly as bad as latex, you can wear these gloves while working with silicone. But know that any silicone left in DIRECT contact with nitrile will not cure. I accidentally left a finger of a glove on the edge of a mold, and it left a little area of uncured silicone directly underneath it. The silicone on the gloves themselves will also not cure, so wipe them down with rubbing alcohol before you take them off if you want to reuse them.
Sulfur
Certain types of modeling clay contain sulfur. Whatever you do, don't sculpt with any clays containing sulfur. It will leave a residue in your molds and prevent silicone from curing. Monster Makers and Prima (NOT Roma!) Plastilina are recommended for sculpting as they are sulfur free.
Ultramarines
A beautiful blue mineral pigment, ultramarine is unfortunately not okay to use when painting your tail. It will inhibit silicone cure and your paint will remain goopy forever.
Ferric Ferrocyanide
Another beautiful blue pigment. This one doesn't prevent silicone cure but does really slow it down. I use it in painting and it takes about twice as long to cure as pigments without FF.
Acrylic paint
I tested this because I was really excited about the possibility of using acrylics to tint silicone, since they come in so many pretty colors and are super cheap. It did not go well. The paint cured eventually (after 2 weeks!) but had a very squishy texture and didn't stretch in the same way as the silicone underneath.
Certain Bras
My first attempt at making a scale top was using a strapless bra from Aerie as the base. The silicone I used to attach bra to scales cured just fine on the band, but did not cure over the cups, leading me to believe there was some kind of foam or rubber in the cups. Always test! And if you come across a line of bras that works just fine with silicone, please share with the rest of the class!
Silpoxy
A special silicone glue made by Smooth On. This only seems to be an issue for me during painting, as un-thinned silicone dries cures over silpoxy with no issue. I attached a pair of extra fins using silpoxy and then painted to blend it into the rest of the tail. The paint cured fine everywhere except right on top of the silpoxy. If you're going to paint directly on top of silpoxy, I recommend using Smooth On's Psychopaint rather than Dragonskin, as that cured with no issue.
E6000
This glue is great for a lot of things, but silicone isn't one of them. I made the mistake of building a mold box with this stuff and the silicone wouldn't cure where it was in contact with the glue.
Duct Tape
The rubber in duct tape can prevent silicone from curing and will leave a residue even after the tape has been removed. If you must use tape around your molds or tail, stick with clear packing tape.
Cold and moisture
Cold or wet weather will make your silicone cure much more slowly. The optimal temperature for working with silicone is around 70F, so turn up the heat if you're working in a cold space.
Gremlins
Sometimes, silicone will just not cure for no reason at all. I'm convinced there are tiny gremlins murmuring evil incantations over my molds.
Latex
A type of rubber found most commonly in gloves and sometimes used to make molds. NEVER use latex gloves when working with silicone. Don't even have it in the same room. Even the residue on your hands or anything you've touched can cause silicone to get angry and refuse to cure. Latex molds are completely out the question, as your silicone will never cure in a latex mold.
Nitrile
Another type of rubber glove. Not nearly as bad as latex, you can wear these gloves while working with silicone. But know that any silicone left in DIRECT contact with nitrile will not cure. I accidentally left a finger of a glove on the edge of a mold, and it left a little area of uncured silicone directly underneath it. The silicone on the gloves themselves will also not cure, so wipe them down with rubbing alcohol before you take them off if you want to reuse them.
Sulfur
Certain types of modeling clay contain sulfur. Whatever you do, don't sculpt with any clays containing sulfur. It will leave a residue in your molds and prevent silicone from curing. Monster Makers and Prima (NOT Roma!) Plastilina are recommended for sculpting as they are sulfur free.
Ultramarines
A beautiful blue mineral pigment, ultramarine is unfortunately not okay to use when painting your tail. It will inhibit silicone cure and your paint will remain goopy forever.
Ferric Ferrocyanide
Another beautiful blue pigment. This one doesn't prevent silicone cure but does really slow it down. I use it in painting and it takes about twice as long to cure as pigments without FF.
Acrylic paint
I tested this because I was really excited about the possibility of using acrylics to tint silicone, since they come in so many pretty colors and are super cheap. It did not go well. The paint cured eventually (after 2 weeks!) but had a very squishy texture and didn't stretch in the same way as the silicone underneath.
Certain Bras
My first attempt at making a scale top was using a strapless bra from Aerie as the base. The silicone I used to attach bra to scales cured just fine on the band, but did not cure over the cups, leading me to believe there was some kind of foam or rubber in the cups. Always test! And if you come across a line of bras that works just fine with silicone, please share with the rest of the class!
Silpoxy
A special silicone glue made by Smooth On. This only seems to be an issue for me during painting, as un-thinned silicone dries cures over silpoxy with no issue. I attached a pair of extra fins using silpoxy and then painted to blend it into the rest of the tail. The paint cured fine everywhere except right on top of the silpoxy. If you're going to paint directly on top of silpoxy, I recommend using Smooth On's Psychopaint rather than Dragonskin, as that cured with no issue.
E6000
This glue is great for a lot of things, but silicone isn't one of them. I made the mistake of building a mold box with this stuff and the silicone wouldn't cure where it was in contact with the glue.
Duct Tape
The rubber in duct tape can prevent silicone from curing and will leave a residue even after the tape has been removed. If you must use tape around your molds or tail, stick with clear packing tape.
Cold and moisture
Cold or wet weather will make your silicone cure much more slowly. The optimal temperature for working with silicone is around 70F, so turn up the heat if you're working in a cold space.
Gremlins
Sometimes, silicone will just not cure for no reason at all. I'm convinced there are tiny gremlins murmuring evil incantations over my molds.