Silicone Types, Properties And A Cheap Option.

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Fayne

New Member
I just sent this info to a friend and thought others could use it.
Feel free to make additions or corrections and add pics if you'd like as I won't be to this step for a while.

Info......
I've been looking into different types of silicone but remember I look at things from a technical angle often as opposed to a brand name angle. I found info that might help you out a ton.
There are 2 kinds of silicone:
Platinum or addition cure, and
Tin or condensation cure.
Both types can come in RTV or room temp. vulcanising or can need heat to cure.
More often the platinums need added heat and are picky about what they touch, thus the name addition cure. These are the ones that cause issues around latex or around sulpher based clays. A lot of the FX stuff you'd use for skins and masks are platinum cure silicones. Platinums won't often (maybe ever) bond to fully cured silicone of any type so new coats are added while tacky.
Tin cures are more often found in RTV variants with an "eaqual parts" mix and are extremely forgiving about chemicals present.
They can often (depending on manufacturer and product) be used around sulpher clays without issue. These are often used for box molds but are a bit weaker (tear strength) than the platinums that are often used for glove molds though you could use either and treat it with care as should be done anyway.
Tin silicone cures by using humidity (not liquid water) and has an oil as a biproduct (small amounts) This is why it's called condensation cure and why it doesn't always need a mold release to make though oiling or waxing to keep a mold in shape is still necessary.
100% silicone caulking like the GE stuff is a Tin/condensation cure but is packaged in the absence of moisture so ppl think of it drying in the traditional sense of losing moisture though it's actually gaining water and losing oil. It already has a thickening agent and doesnt get moisture if used too thick. To use it as a mold you would either thin with naptha or mineral spirits for your first thin coats. I'd just use brand name for the first few coats so I don't soften my clay and screw up the work. For subsequent coats you can use the GE silicone (not the regular caulking / only 100%) and to ensure it dries /catalyzes mix it with a small amount of acrylic paint which has a chemical that helps to catalyse the tin cure silicone. Not to mention the paint will show how well it's mixed. I'm thinking of experimenting with naptha or mineral spirits and acrylic paint all together to make it brushable but make bubble poppable and easier to avoid. I'd only do that on my later cots of coarse.
I almost forgot to mention, within each family silicone types are pretty much the same until catalyst is added. In other words the silicone part is often similar from type to type within it's respective tin or platinum family but the catalyst part of the mix could have a load of different ingredients to impart the different strengths and qualities of each type or brand.
 

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Usurper

Well-Known Member
and what does this have to do with PREDATOR WEAPONS AND ARMOUR? or ANY of the tags you linked.?

Please stop abussing the taggin system by spamming every Predator tag you can think of.


sigh

MOVED.
 

Effects Guy

New Member
Silicone caulking is not tin cure, it is acetoxy cure. In fact there are not two types, there are many more. Platinum cure, tin cure, gold cure, acetoxy cure, etc. Also, heat speeds up cure on platinums but it is rarely essential. Heat also speeds up cure on tin silicones but not as intensely as with platinums.

I hope that helps.
 

Fayne

New Member
Every bit of info helps Thx.
There are a lot of sources of this info and I've already weeded through some really wrong stuff like mixing water and good info is always appreciated.
 

MEANGENE83

Sr Member
I was reading the technical info on my smooth on Platinum Silicone. Was a shore hardness of 16 I believe.

It said if you put the mold in the oven at 140. The mold will set in 2 hours. Down from a regular 6-7 at room temperature. Was really surprised.

Just though I would add that in the mix since Effects Guys mentioned it.

It also stated sulfur based clay will inhibit the cure completely.
 

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Fayne

New Member
Thank you both for the additions. I've been doing some more research and found that others have tried acrylic paints instead of pigments with platinum (unsure of brand) and the glycerine kick started it just like with the acetyl so I wonder if small amount can be used in any type for a faster cure.
 

Fayne

New Member
Oh hey does anyone know of a brand (tin or platinum) that withstands methyl methacrylate hardening and damaging it for many pulls? Some of my old molds only get about a dozenish pulls then die a horrible death. I've tested some samples of other stuff without the issue but I think it's not so much the heat or chemical by themselves as it's the chemical change when monomer causes the plastic to change it's chains that causes some horrible effect to the silicone. Maybe it deposits much faster than urethanes, etc?
 

Effects Guy

New Member
What kind of resin are you casting in these molds that they fall apart after 12 castings? I have never seen such a thing? What silicones have you used? What hardness levels?
 

Fayne

New Member
It's not likely one of the resins you've used. I don't have the silicone info as it's been a long time but they were decent tin cure that others have great luck with doing 3d arts here. My plastic is a denture material normally cast in plaster and the stuff totally kills my molds. Put it this way... If you spill uncured momomer on nitrile gloves it melts them. Oh also had some more info on the acetyl. I tried aprox. 4-5 oz. of each white and clear with around 1-3 oz. of mineral spirits and less than 1/2 oz. acrylic paint per test. The stuff bonds to itsself and in these tests didn't bond to the sealed porcelain plate it was in but also didn't bond to little cut bits and larger chunks of old tin cure. It smells of mineral spirits a day later so I expect shrinkage as it loses the spirits. I tried again without the mineral spirits to thin it and it started curing while mixing. It made a really strong patch and bonded great to the previous stuff but was much denser and firmer. The thicker stuff feels like shoe rubber while the thinned stuff is really soft and skin like in texture. Both stretch a bit though the denser one is harder to do but neither resists tearing very well or bonds to other silicones. The thinned one leeches into clay and ruins the sculpt so mold making ability would be limited depending on many factors,what is being molded and have other silicone layers such as platinum or tin been laid down 1st. I think when I make my mold after sculpting, I might do a brushable tin cure glove with mothermold this time and use this stuff as filler for turning a later glove mold into a box mold (definately needs release agent in the thicker mixes) or maybe for masks since it feels so close to skin but with nylon or sports fabric to strengthen it and with a more inert smelling thinner. maybe silicone oil or even lard, more experiments I guess.
 

Effects Guy

New Member
Silicone fluid will not help to much. I love my tin stuff, 2125 from MPK Enterprises. I cast dental acrylic in often enough, and have had no issues. It is simply the best tin silicone I have ever seen. Might be worth a shot.
 

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Fayne

New Member
update to a fiew of the items here. acetoxy is a condensation cure like tin but needs to be thin or use a kicker which will weaken it. mineral spirits and naptha can thin acetoxy but also weakens it then evaporates out so it shrinks and stinks. I'm considering an experiment with cheap brand acetyl mixed with tin cure to a brushable consistany and done in 1/2 inch-ish coats. the weakness in my old molds may have been brand but some were accelerated by doubling catalyst and those will likely fail sooner. looks like wrong temp either direction, kickers, and wrong ratio will all weaken it so although they can be handy things to do for a quick pour, it had better be a short run to justify that. lastly, does anyone know of anything cheaper than econosil which is a tin cure @ under $90 a gallon before shipping?
 

Effects Guy

New Member
Not sure where you are located. Using acetoxy cure silicone for molds can work in a pinch, but you will be lucky to get more than one casting out of it, and they can shrink and distort terribly, especially when cast thickly. If you brush it on really thin, like 1/32 inch or so, and built up to about 3/4 inch in many thin layers, it may work. But, that could take days. I hate to say this, but sometimes it pays not to cut corners. My favorite mold silicone in the universe is only $99.99, and it is amazing. Cures in 2 hours with the normal catalyst, and lasts for many years. I have some molds that are 5 years old, and show no sign of degradation. You save even more if you buy the 5 gallon kit.
 

Fayne

New Member
That's most likely the direction this'll have to go. I've done some smallscale tests and I agree. Each of the cheap methods, whether caulking and soapy finger or thinning it to pourable have their issues. These might be great options for an extremely short run but I want mine to last many years.
 

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