Silicone Caulk as a molding material

[VulgarDragon]

Hi, I was doing an experiment on the use of silicone caulk from hardware store as a molding material, so I thought I would post a tutorial on it. It is not a good replacement for professional molding material that are made specifically for sculptures, but it might work as an alternative if you're tight on cash or want to make a "waste" mold. Be warned it is very messy and smelly. Silicone caulk gives off acetic acid as a byproduct, so unless you want your house to smell like a big pot of boiling vinegar, I suggest mixing it someplace with good ventilation.

I was able to successfully make a mold for one of my sculpts I made from Plasticine (modeling clay), although it didn't turn out perfectly...the final casts had some bubbles in it. Might be good to consider for recasting pieces in wax for further detailing.

[VulgarDragon]

The results:

[taurn7]

That is pretty neat Mike! What does the glycerin do?

[maddmaestro]

That is pretty neat Mike! What does the glycerin do?

I would imagine it works a s a mold release agent? Not sure though... Mike you changed your name? I wasn't even sure who you were... lol. Nice tutorial! I have been eager to try molding something besides my own hands and face... might have to give this a try since I'm super broke! Thanks!

Maddmaestro:afroboy:

[VulgarDragon]

The glycerin helps the caulk to cure more evenly and faster. If it isn't added, you will get areas where caulk is still uncured, especially in thicker areas which will take days or even months to fully cure. The acrylic paint is for making sure it is mixed evenly, although it might do help with the process. Silicone caulk is designed to be an adhesive and adding glycerin seem to help tone down its stickness a bit. Still, I would be very careful about applying it to something other than oil clay or wet clay without a good mold release. The glycerin is sold at drug stores as a laxative :)

Madmastero- Good to hear from you...yeah I changed my name because I thought it would better to have my name match my website.

[Mah ' Crub]

Good thinking!!! Wish I had thought of that!!!! I see you made a mother mold. You may want to explain what that is to your tut. audience.
Great job, { Oh yes, love the sculpt, great face and personality,}

Mah ' Crub

[Smolder]

Great tutorial! And yes, it really, really works! Last Halloween I wanted a lot of skulls, but didn't want to drop five bucks a pop on them. Using the method VulgarDragon has illustrated, along with some cans of insulation foam, I was soon swimming in skulls. The only thing I did differently was to use a piece of ice to smooth out the silicon instead of dishwashing liquid. After reading this I'm fairly confidient that Vulgar's method is better (no cold fingers :p )

From what I understand, Silicon caulking cures via exposure to moisture. In normal use there is enough moisture in the air to cure a thin line along a window sill. When applied thicker than about half an inch the surface will cure and seal the inside away from the air and the moisture it needs to cure. By mixing in glycerin and acrylic paint you ensure that there is enough moisture through out the caulk to make it cure.

It is still possible to put it on too thick, anything over an inch is asking for a long cure process. Happily, it sticks to itself, and it is possible to add a layer and come back in a few hours and add another. Layering also helped me avoid bubbles, as I could first apply a thin layer to get the details.

This is fun and cheap, and fantastic for anything where details don't need to absolutely perfect.
http://i795.photobucket.com/albums/yy232/smolder_bucket/Caulk%20Skulls/SkullA.jpghttp://i795.photobucket.com/albums/yy232/smolder_bucket/Caulk%20Skulls/SkullB.jpg
http://s795.photobucket.com/albums/yy232/smolder_bucket/Caulk%20Skulls/

[Joshua A.C. Newman]

I wonder if there's something you can add to decrease the viscosity to get a good primary surface before building up the rest with goop.

[VulgarDragon]

I wonder if there's something you can add to decrease the viscosity to get a good primary surface before building up the rest with goop.

It's possible to thin it out with some solvent like xylene, but that's pretty dangerous. Besides, it weakens the silicone and there is a great deal of shrinkage, too.

Mah' Crub : Yeah, I built mother mold out of plaster and newspaper so the mold would stay put. I have pics of the process so I will have to post them when I get the chance.

Smolder : Cool! Glad to see that I'm not the only one to use the process. I still have to perfect my technique...my mold had too many bubbles.

[agrmrs]

wow very mice sculpts & a unique method ....... thanx for sharing with us :)

[Mah ' Crub]

Just thinking out loud here, but I wonder if you mixed water, or even latex paint into the caulking, ,,, would that enhance the viscosity enough to allow you to pour it on, rather than a thick glopy consistency.The extra water could also enhance the drying process. I have used this stuff for years in the kitchen cabinetry industry, and use water to smooth out the joints with great success, and it now makes sense that the water helps the drying process.
You know this could turn out to be a fairly good alternative to reg. silicone which is financialy out of reach at the moment.
Thanks for shareing this innovation! It could help keep the costs down, while allowing the creativity to continue !

Mah ' Crub

[Joshua A.C. Newman]

Yeah, you use water for silicone cleanup, too.

[TeaMonster]

Way Cool, well done Mike. Cheers for the tutorial, might have to try it out :)

[dark_wraith]

great tutorial.

I have been experimenting recently with silicone caulking as well.

I have found if you cut the whole end of the caulking tube off and push out the silicone into the water as one large mass, rather than a thin stream, it is easier to avoid getting too many air bubbles in the silicone.


To get small details I have also tried brushing on a thin layer of silicon right from the tube and submerging the whole sculpture in water to cure the silicone. I have moderate success with this method. The silicone is very sticky but I didn't think of adding glycerin to cut down the tackiness. I will have to try that method.

Anyway thats my two cents.

[MikeMakesModels]

I've read about this before, but it's great to see it in action and working. Thanks for posting. :)

[Fovos]

that was great thank you VulgarDragon, good to know the alternative not so expensive ways out there. How easy it was to apply it on your sculpt?...it was more like pouring it or brushing it?

[Kelg]

Polytek used to have a catalogue where they rated different casting and mold making materials. Silicon caulk got the best overall rating-even when compared to their own mold making silicons(this was around 10 years ago, maybe something better has come along). For endurance, shrinkage, heat and tear strength it can hold up really well.

I have heard of thinning it but I fear it may affect its longevity.Sulphur clay can mess with it especially when using casting resins--I had a silicon mold "eaten" by it once.

I have to "trowel" the silicon caulk on using small tools and fingers and then apply moisture to smooth it over and fill in cracks. After a couple of skim coats I can then mush on a half an inch thick amount.
If you dont do that then you can get uncured silicon trapped against the piece(at least when using oil clay). I never ever get airbubbles through this method. It seems tedious at first but once you get through the skim coats its fast.

[Joshua A.C. Newman]

I have heard of thinning it but I fear it may affect its longevity.

I know that, with epoxy, when you reduce viscosity by adding alcohol or acetone, you keep the molecules from getting close enough to polymerize and wind up with a really weak material. I can see that happening with silicone, unless perhaps it was thinned with water, which is what it bonds with to polymerize.

So why glycerine and not water? What does the glycerine do?

I'd wager that it would be worth building an outer shell of fiberglass or plaster to help it keep its form if the object was more complex.

[Joshua A.C. Newman]

Oh, another thing: Aloe gel might work (it sure does for sunburns), but you can also get PVA — polyvinyl alcohol —in anyplace that deals in polymers. I think I got mine from a boatbuilding place.

Don't confuse it with PVA —polyvinyl acetate. That's glue. You will be very, very disappointed.

I bring it up because the stuff really isn't very expensive and works really well. You can airbrush it on or just use a spray bottle and the resultant film is very thin.

[Kelg]

I always do an outer shell so it can keep its shape. You have to make sure that you dont get sloppy when doing the final coating of the silicon--if you leave little wispy things or not appropriate notches then the mother mold might not properly fit into the rubber casing.

I usually end the rubber phase by extruding around the edge of it like I am decorating a birthday cake and add criss crosses over the surface.

Just enough for the outer shell to have something to grip.

Speaking of epoxy--my latest casting method has been to use the two part magic sculp type epoxy clay and make it very wet--to a paste
and then jam that into the rubber mold. When it hardens(if you press it into the surface of the mold properly) it creates a perfect copy. Due to the water, it can take a little longer for it to fully harden and it appears a bit brittle at first but after weeks it seems to be just as good as if you had mixed the two parts without excessive water.
And unlike resin, no shrinkage that I can detect and it doesnt react to a mold that has used sulphur clay.

[VulgarDragon]

that was great thank you VulgarDragon, good to know the alternative not so expensive ways out there. How easy it was to apply it on your sculpt?...it was more like pouring it or brushing it?

It's like a thick and sticky gel...not quite that easy. I took a stick and spread it around the best I could, just like icing a cake. I wish there was a good way to thin it. I am considering buying a sample of silicon mold from Smooth-on and use it as the first layer for detail and then use the caulk for additional layers to bulk it up. Not sure if it would work, but both are silicon based so I assume they will stick together even though they are different formulations.

Anyway, here's my finished product, all painted up. I had to add bits of sculpey to fill in some holes, but not that much.

[dark_wraith]

I am considering buying a sample of silicon mold from Smooth-on and use it as the first layer for detail and then use the caulk for additional layers to bulk it up. Not sure if it would work, but both are silicon based so I assume they will stick together even though they are different formulations..

I have tried this and they stick together fairly well. If you really pull they do delaminate but you really have to pull. That was with a smooth finish on the smooth-on coat, with a bit of texture they should stick permanently.

I still need test further but the silicone caulking seemed to shrink and distorted the mold but it may have been another variable.

[Kelg]

I have never tried caulk with polymer clay--but paint thinner can cause the silicon to get warped.
I stick to the 100 percent pure silicon--they have newer types, I found with roma plastilina that it didnt cure evenly-or seemed weaker than the original kind.

[VulgarDragon]

I have never tried caulk with polymer clay--but paint thinner can cause the silicon to get warped.
I stick to the 100 percent pure silicon--they have newer types, I found with roma plastilina that it didnt cure evenly-or seemed weaker than the original kind.

The sulphur in some clays can interfere with the ability of the silicon to cure fully, so in that case, the clay will need to be coated with something. I did an experiment by painting the modeling clay over with acrylic paint, and it seemed to work well...the silicon didn't stick to it at all. However, it was kind of a pain to remove the paint off the clay...I had to scrape it off. Might work if you don't mind wasting a little bit of clay that way.

I also did a very small piece of baked sculpey, which I brushed with soap solution and let dry...seemed to work but I will need to test it further.

[Kelg]

The sulphur in some clays can interfere with the ability of the silicon to cure fully, so in that case, the clay will need to be coated with something. .

** I never had any problem with it curing using roma plastilina-(except when using the newer silicons)-I have made caulk molds without any sealer for the clay..the problem arose when i tried to cast in resin--it caused a reaction--the resin surface would end up strange. I am told its the sulphur.
I used to cast with hydrostone so I never had a problem with the casting material getting messed up.

But now regardless I always use some minwax or polyurethane varnish on the sculpture when I make molds-makes it easier to clean out anyway, although the resin reaction problem still happens(the last time I tried it).

[The Dark Power]

I use silicon caulking (or sealant as it's called in the UK) to paint silicon rubber puppets. I thin it with white spirit so you can probably use a similar technique to thin your caulking for mold making. I wouldn't add too much though as if you make it too runny it can interfere with the silicon curing. You can also use white spirit to smooth the mold down when you're done.

[Aizkur]

increible tutorial,thanks for sharing whit us,really I going to try make a mold with your tecnique,thanks.

[Mah ' Crub]

Dark Power, I am not familiar with the term," white spirit." Could that be the same thing as our "mineral spirits," which is really, just paint thiner for oil based paint. It is very thin, clear, and oily. Or is your, White Spirit something else altogether? I am wondering if it may be more alcohol based. If so that may actually help with the curing since alcohol dissapates water. Just brainstorming. In theory,, maybe,, reality? Thats something I try to avoid.
Cheers,
Mah ' Crub

[SavageGoldfish]

Why have I not checked this out before? EXTREMELY useful! Thank you very much for sharing, I shall have to give this a try!

[Kelg]

you can also use clear silicon caulk with oil paints mixed in to get a translucent skin colour for a casting material. I have used to to make a corpse prop.

You make a plaster or ultracal mold and then paint in the tinted silicon layer by later. If yous tick an orange or red tinted translucent layer inside-you can eventually make it glow in a flashlight-like the ears can appear to have tissue inside it.
Good for lifesize props anyway.

[The Dark Power]

Dark Power, I am not familiar with the term," white spirit." Could that be the same thing as our "mineral spirits," which is really, just paint thiner for oil based paint. It is very thin, clear, and oily. Or is your, White Spirit something else altogether? I am wondering if it may be more alcohol based. If so that may actually help with the curing since alcohol dissapates water. Just brainstorming. In theory,, maybe,, reality? Thats something I try to avoid.
Cheers,
Mah ' Crub

Hi

Yeah Wikipedia tells me it's the same stuff. I must admit even stuff that's been really thinned down has managed to cure to a degree, kinda going abit like a gel.

I should say though that while caulking is useful, it's no substitute for the real stuff. If you're in the US you guys should check out Smooth-on (http://www.smooth-on.com/Special-Effects-an/c1241/index.html) or if you're in the UK Mould Life (http://www.mouldlife.co.uk/) is excellent, I recently bought some stuff from them.

[Das_fenster2000]

When you add the oil paint for color, what did you thin it out with? i'm looking to make silicone monster hands, but only want to use the silicone as a skin, then fill them with foam....just need a good way to make the caulk pourable

[sloopster]

you can thin calking down so its like water ( a good trick for airbushing with it) but one thing you have to watch out for is the pigments in the materials your casting i think black in new clay has a habbit of inhibiting the calking going off but its a bit hit and miss but if your short of funds then its a great mcgiver method!

[houseoficons]

wohoooooo!!!!!

[freakinacage]

Outstanding, ta for sharing

[SuPa-]

Hey thanks a lot for the tutorial! I just tried this out, with some slight variations, and it seems to hold detail really well! The only thing I did differently was that I directly applied caulk from the gun onto the skull and brushed it around. After letting that layer cure for a bit, I followed your method.
You can also use another silicone product, like from smooth-on, brush on a layer or two of that, and then bulk it out with the caulk. I tested this and can confirm that it works quite well.

I'll try to post some pics later, but it might be awhile.