Replies to This Discussion

Permalink Reply by michelangelo on May 18, 2015 at 8:27am

hi

after a lot of time a restart with my experiment with Platsil gel 10.

Anyone know witch is a right glue to paste the silicon on the plastic or fiberglass?

thanks!

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Permalink Reply by michelangelo on May 19, 2015 at 12:50am

Hi

anyone tried it?

Sil-Poxy Silicone Adhesive 

smooth on

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Permalink Reply by michelangelo on June 5, 2015 at 4:05am

Hi

so the best way to paint by airbrush is Rs fluid silicone + silc pig?

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Permalink Reply by Doug Henderson on October 10, 2017 at 4:05am

A cheap trick to bond silicone to many different surfaces is to coat the surface that you want silicone to bond to with shellac. You can use most silicones as an adhesive as long as you are not trying to use a platinum silicone to glue a tin silicone. But you can go the other way.

For example: you can put tin silicone onto cured platinum silicone and you can put silicone caulk onto cured tin or platinum, but platinum won't cure against tin or caulk.

As far as painting, using brushes or airbrushed has more to do with the effect you are going for. Airbrushing leaves less chance for accidentky building up too much thickness.

I recommend pre tinting your silicone with silicone pigments if it's platinum silicone. I've also used oil paints in small amounts. Dry pigments work well too in small amounts. Makeup ponders, tempers powder, flocking, lots of options. Tin silicones are even more forgiving. I mostly use the cheapest oil paints I can find.

I know there are a lot of other painting systems out there, but I just use GE Silicone 1 as my paint base. I thin that with either Naptha or d-limonene (preferred - expensive, but totally non toxic). Some use Coleman fuel or mineral spirits.

I color the silicone caulk with oil paints if I want a long working time, or acrylic if I want it to set up fast.

The standard mix ratio is 4 parts silicone to 1 part pigment, thinned with about 5 parts solvent. It can vary a lot from there, but I don't suggest much higher concentration of pigment. You can add tons of solvent to create washes and translucency.

As far as matting the silicone to eliminate shine, I've used powdered sugar for years. When the paint job is done, I spat a very dilute layer of clear silicone over the whole thing and then Shane on a very heavy layer of powdered sugar. DONT TOUCH IT AFTER THAT! I let it cure overnight, then rinse off the sugar. This technique was taught to me many years ago by Tom McLaughlin and I stuck with it. Now I prefer to use cabosil mixed with clear GE silicone 1 and heavily thinned with solvent. I airbrush this on and it dries very quickly, leaving an almost dead-flat sheen. If it's too flat, I might lightly spray over that with plain GE silicone caulk thinned with solvent. Just to leave tiller droplets to bring back a tiny bit of shine.

Another cool trick that most people don't know is: you can make silicone molds with silicone caulk. And you can do solid castings with it. I only suggest GE silicone 1 for this purpose. It does shirk a bit, so don't use it to make molds or castings that need to be super accurate, but it works really well. Right now I'm casting fish out of caulk for an upcoming film project and it works really beautifully.

The secret it to mix a small amount of acrylic paint into the caulk. This catalyze sit and makes it cure the whole way through. If you use a tiny bit of acrylic, you get a beautiful translucency and longer working time. More acrylic will make it set faster and makes it more opaque. I use clear acrylic medium if I want the silicone to stay clear.

Hope these tips are helpful!

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Permalink Reply by Doug Henderson on October 10, 2017 at 5:11am

I just re-read my post and realized it sounded like I'm saying I'd only pre-tint platinum silicone, but I think I lost my train of thought. :)  I pre-tint all silicone casts. It's nearly impossible to paint over clear silicone, unless you are making a jellyfish or something similar. 

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Permalink Reply by Doug Henderson on October 10, 2017 at 5:43am

I found a ton of misspellings in my post above, so please see my corrections in bold below:

Doug Henderson said:

A cheap trick to bond silicone to many different surfaces is to coat the surface that you want silicone to bond to with shellac. You can use most silicones as an adhesive as long as you are not trying to use a platinum silicone to glue a tin silicone. But you can go the other way.

For example: you can put tin silicone onto cured platinum silicone and you can put silicone caulk onto cured tin or platinum, but platinum won't cure against tin or caulk.

As far as painting, using brushes or airbrushes has more to do with the effect you are going for. Airbrushing leaves less chance for accidentky building up too much thickness.

I recommend pre-tinting your silicone with silicone pigments. In platinum silicone, proper silicone pigments are best, but I've sometimes used oil paints in small amounts. Dry pigments work well too in small amounts. Makeup powders tempera powder, flocking, lots of options. Tin silicones are even more forgiving. I mostly use the cheapest oil paints I can find.

I know there are a lot of other painting systems out there, but I just use GE Silicone 1 as my paint base. I thin that with either Naptha or d-limonene (preferred - expensive, but totally non toxic). Some use Coleman fuel or mineral spirits.

I color the silicone caulk with oil paints if I want a long working time, or acrylic if I want it to set up fast.

The standard mix ratio is 4 parts silicone to 1 part pigment, thinned with about 5 parts solvent. It can vary a lot from there, but I don't suggest much higher concentration of pigment. You can add tons of solvent to create washes and translucency.

As far as matting the silicone to eliminate shine, I've used powdered sugar for years. When the paint job is done, I spray a very dilute layer of clear silicone over the whole thing and then shake on a very heavy layer of powdered sugar. DONT TOUCH IT AFTER THAT! I let it cure overnight, then rinse off the sugar. This technique was taught to me many years ago by Tom McLaughlin and I stuck with it. Now I prefer to use cabosil mixed with clear GE silicone 1 and heavily thinned with solvent. I airbrush this on and it dries very quickly, leaving an almost dead-flat sheen. If it's too flat, I might lightly spray over that with plain GE silicone caulk thinned with solvent. Just to leave little droplets to bring back a tiny bit of shine.

Another cool trick that most people don't know is: you can make silicone molds with silicone caulk. And you can do solid or hollow (brush up) castings with it. I only suggest GE silicone I for this purpose. It does shrink a bit, so don't use it to make molds or castings that need to be super accurate, but it works really well. Right now I'm casting fish out of caulk for an upcoming film project and it works really beautifully.

The secret is to mix a small amount of acrylic paint into the caulk. This catalyzes it and makes it cure the whole way through. If you use a tiny bit of acrylic, you get a beautiful translucency and longer working time. More acrylic will make it set faster and makes it more opaque. I use clear acrylic medium if I want the silicone to stay clear.

Hope these tips are helpful!

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Permalink Reply by Simon Tytherleigh on October 10, 2017 at 11:35am

Hi Doug. Thanks for sharing all your tips. I too have found icing sugar to be really effective. Will look up d-limonene, which I haven't come across. I tend to think we're not using naptha in large quantities so I don't wear a mask. But anything that is less toxic has to be good.

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Permalink Reply by Simon Tytherleigh on October 11, 2017 at 3:27am

Doug, can I ask a question about the GE silicone caulk you use? 

Is it an acetoxy silicone? Presumably it does not contain fungicides, as it advertises itself as 100% silicone.

I am just wondering about the other silicones available, and whether they are also suitable. I have used glazing (non-acetoxy) silicone for attaching hair to Platsil, but never tried using it for painting. My hunch is that it would be fine for that too. So just wondering what the differences might be.

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Permalink Reply by Doug Henderson on October 13, 2017 at 11:15pm

Hi Simon,
The GE Silicone 1 has no fungicides and it is acetoxy, yes. The Silicone II does have fungicides and does not work for my purposes. I made a mold with Silicone 11 last year and it never cured. Accidentky grabbed the wrong tube.

I've never tried glazing Silicone. Not sure what the difference is, but since you have had success with it, maybe do a little test batch with acrylic added to see if it works and let us know.

I do know that some colored silicones say 100% Silicone, which is odd since they obviously contain pigment. I've never tried those either.

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Permalink Reply by Simon Tytherleigh on October 15, 2017 at 2:51am

Hi Doug. Thanks for the info. 

Glazing silicone is not acetoxy, that's the difference, so it may work differently, although it seemed fine for the hair patches.

I got some d-limonen today, so will give it a go too. Thanks for all the tips!

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Permalink Reply by Doug Henderson on October 15, 2017 at 4:13pm

Oh cool! I think you'll love D-limonene. It's awfully expensive compared to other solvents, but I think it's woth it.

I used some spray shellac the other day and the silicone bonded better in some places than others. I think it may be different than the canned shellac. What I did notice is that there's a different bond depending on how freshly the shellac was applied. I did a control test and I'll check it in the morning.

There's also a product from Smooth-On called "Inhibit X" that seals a contaminated surface and allows Silicone to cure against it. For instance, you can cast Silicone in a mold that was previously used for foam latex, which otherwise wouldn't work. I haven't tried it yet, but the product description footnotes that Inhibit X can cause silicone to bond to that new, sealed surface and warns to use a release to prevent that. I wonder if it would also help Silicone bond to fiberglass and metal, etc.

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Permalink Reply by Doug Henderson on January 16, 2018 at 1:40pm

I forgot to report that silicone colored with acrylic doesn't stick well to the shellac and is probably the cause of most issues I've had randomly in the past. it is fine with a little oil paint, but works best with just untinted silicone caulk first.

Happy New Year everybody!

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