Silicone caulk mold making
- Thread starter ERen89
- Start date
inblackandlace
Active Member
I wouldn't really recommend the caulking stuff unless it's a very small, not very detailed piece. I used it for my glass war axe, but only for the spikes, not the blade.
There are a couple of issues with using silicone caulk as a mold making material. The first is that unlike silicone mold making rubber, the caulk is gonna stick to everything! Make sure to use some sort of mold release. Vasilene might work, but I would do a test fist. The other problem is that silicone caulk cures by evaporation rather than by mixing in a catalyst. So you'll have to build it up in thin layers, letting each dry completely before applying the next. For all the hassle, I'd just recommend you buy some real RTV silicone mold rubber. It's not going to end up costing all that much more than the caulk and will be a whole lot easier and faster to use!
ERen89
Active Member
After my first attempt, I have learned this now, the core of the block did not cure at all after 24hrs. so that was my mistake for doing it all at once. I basically want to find the most affordable way to make silicone molds. I may end up just doing the mold making rubber like you mentioned.
Blaxmyth
Sr Member
Definitely agree with this! Cost me a lot of time and even more money to learn this lesson.
DtailedREPLICAS
Active Member
Smooth on is very popular in the US and so is probably pretty affordable.
If you're overseas, then it probably wont cost you that much more for actual mold making silicone. If you're in Australia, like me, then you'd know that getting RTV here means spending hundreds and hundreds of dollars for quantities that cost under a hundred as caulking silicone.
There are tricks to using caulking silicone for mould making, you just have to understand the science of how it cures. As Dave pointed out, it cures through evaporation. It actually takes moisture out of the air and uses it in a chemical reaction, resulting in the production of acetic acid as a by-product. This is why caulking silicone smells like vinegar while its curing. Because vinegar IS acetic acid.
Knowing how it cures you can quickly work out why is doesn't cure in thick layers. Quite simply, because the lower layers don't have access to moisture from the air. Which is where the solution comes from.......adding moisture.
There are two main ways I've experimented with in the past that both work, with their own set of drawbacks.
The first..........
Take a bucket and fill it with warm water and add a decent amount of detergent.
The detergent will stop the silicone sticking to your hands.
Then take a few tubes of 100% silicone caulk and squeeze all of the material into the bucket.
Makes sure your hands are covered in soapy water and then work the silicone under the water into a ball, working moisture into the silicone mass.
Then apply the silicone straight to a sealed, smooth item you wish to mould.
You have to apply it in such a way as to avoid trapping air underneath, and you have to work quickly as the mixture will start to cure rather rapidly from the warmth of the water and the high amount of moisture now in the silicone.
This method is ok for quick, dirty, throw away moulds, where you just want to copy a rough shape for example, that will be later refined. HOWEVER, small bits of cured silicone that hardened before you applied the mixture to your item may ruin your detail.
The other method...........
Take some caulk and squeeze it into an empty soft drink bottle.
Add some mineral turps (known by a hundred other names, so do some research)
Add a few drops of glycerine, and a few drops of acrylic paint.
The glycerine helps to start the reaction, as does the water based acrylic paint. The paint also makes your mould a pretty colour. Win-win.
Then simply shake your bottle to mix the ingredients.
The mineral turps is a solvent and will dissolve your silicone into a liquid like consistency. The more turps you add, the thinner your silicone, and the easier it is to pour and pick up nice details in the mould.
HOWEVER, the turps will evaporate! This means that the mould will shrink! More turps, more shrinkage, less turps, less shrinkage.
But this method should get you buy for something that is single use, or isn't too important. The longer you leave the mould, the more it will shrink, so don't wait.
Of course, neither of these methods are as reliable and produce as good a result as proper RTV or platinum cure silicone, but depending on what you're actually using them for, can be an easy, cheap alternative for only a few bucks.
Normal disclaimers apply. If you ruin something, or burn something down using these ideas, its not my fault. Always TEST FIRST in a house that you're allowed to burn down.
If you're overseas, then it probably wont cost you that much more for actual mold making silicone. If you're in Australia, like me, then you'd know that getting RTV here means spending hundreds and hundreds of dollars for quantities that cost under a hundred as caulking silicone.
There are tricks to using caulking silicone for mould making, you just have to understand the science of how it cures. As Dave pointed out, it cures through evaporation. It actually takes moisture out of the air and uses it in a chemical reaction, resulting in the production of acetic acid as a by-product. This is why caulking silicone smells like vinegar while its curing. Because vinegar IS acetic acid.
Knowing how it cures you can quickly work out why is doesn't cure in thick layers. Quite simply, because the lower layers don't have access to moisture from the air. Which is where the solution comes from.......adding moisture.
There are two main ways I've experimented with in the past that both work, with their own set of drawbacks.
The first..........
Take a bucket and fill it with warm water and add a decent amount of detergent.
The detergent will stop the silicone sticking to your hands.
Then take a few tubes of 100% silicone caulk and squeeze all of the material into the bucket.
Makes sure your hands are covered in soapy water and then work the silicone under the water into a ball, working moisture into the silicone mass.
Then apply the silicone straight to a sealed, smooth item you wish to mould.
You have to apply it in such a way as to avoid trapping air underneath, and you have to work quickly as the mixture will start to cure rather rapidly from the warmth of the water and the high amount of moisture now in the silicone.
This method is ok for quick, dirty, throw away moulds, where you just want to copy a rough shape for example, that will be later refined. HOWEVER, small bits of cured silicone that hardened before you applied the mixture to your item may ruin your detail.
The other method...........
Take some caulk and squeeze it into an empty soft drink bottle.
Add some mineral turps (known by a hundred other names, so do some research)
Add a few drops of glycerine, and a few drops of acrylic paint.
The glycerine helps to start the reaction, as does the water based acrylic paint. The paint also makes your mould a pretty colour. Win-win.
Then simply shake your bottle to mix the ingredients.
The mineral turps is a solvent and will dissolve your silicone into a liquid like consistency. The more turps you add, the thinner your silicone, and the easier it is to pour and pick up nice details in the mould.
HOWEVER, the turps will evaporate! This means that the mould will shrink! More turps, more shrinkage, less turps, less shrinkage.
But this method should get you buy for something that is single use, or isn't too important. The longer you leave the mould, the more it will shrink, so don't wait.
Of course, neither of these methods are as reliable and produce as good a result as proper RTV or platinum cure silicone, but depending on what you're actually using them for, can be an easy, cheap alternative for only a few bucks.
Normal disclaimers apply. If you ruin something, or burn something down using these ideas, its not my fault. Always TEST FIRST in a house that you're allowed to burn down.
Gixxerfool
Well-Known Member
Just copy and pasted this for future reference. Just great Info to have.
Strode
Sr Member
^Agreed. I screenshotted that response. Thank you Dtailed Replicas for such a detailed response
.
Over in the General Modelling section, another user has been attempting to use silicon caulk to mould his helmet and is graciously updating his results. Check it out.
http://www.therpf.com/f11/molding-silicone-diy-store-question-230299/
The video he refers to uses a lot of household and easily available materials.
. Over in the General Modelling section, another user has been attempting to use silicon caulk to mould his helmet and is graciously updating his results. Check it out.
http://www.therpf.com/f11/molding-silicone-diy-store-question-230299/
The video he refers to uses a lot of household and easily available materials.
ERen89
Active Member
Thank you a bunch for your responses. I definitely will do some more research to determine how I want to do this. These posts helped, and thank you DtailedREPLICAS
for your descriptive response regarding techniques.
for your descriptive response regarding techniques.
Last edited by a moderator:
0Hi.
I have been successfully using Silicon 1 caulk to make molds, last one I made was for a large majora's mask (about 13" X 11.5"), you can buy 1 stick of silicone and try to make the mold to experiment, here are some of my recommendations:
Use silicone 1, don't use silicone 2.
Use a wax based release (I make my own), don't use vaseline.
Mix the silicone with corn starch (makes the silicone cure a lot faster) and painter's thinner, experiment with the ratios but use a max. or 10% painter's thinner.
Apply with a small brush 1" max. preferably with an artist's brush, make the first 2 layers thin.
Make small batches of about 40 grams of silicone, larger batches cure very fast int the container not giving you time to apply.
You can mix the silicone with a little bit of artist's oil paint to color the different layers of silicone so you know where you have applied the layers.
I used two sticks of silicone 1 to make my majora's mask mold, at a $13- $15 total cost, I would have spent about $35- $40 using RTV silicone.
I say, give it a shot, buy 1 stick of silicone 1, it's inexpensive and you can learn a lot
I have been successfully using Silicon 1 caulk to make molds, last one I made was for a large majora's mask (about 13" X 11.5"), you can buy 1 stick of silicone and try to make the mold to experiment, here are some of my recommendations:
Use silicone 1, don't use silicone 2.
Use a wax based release (I make my own), don't use vaseline.
Mix the silicone with corn starch (makes the silicone cure a lot faster) and painter's thinner, experiment with the ratios but use a max. or 10% painter's thinner.
Apply with a small brush 1" max. preferably with an artist's brush, make the first 2 layers thin.
Make small batches of about 40 grams of silicone, larger batches cure very fast int the container not giving you time to apply.
You can mix the silicone with a little bit of artist's oil paint to color the different layers of silicone so you know where you have applied the layers.
I used two sticks of silicone 1 to make my majora's mask mold, at a $13- $15 total cost, I would have spent about $35- $40 using RTV silicone.
I say, give it a shot, buy 1 stick of silicone 1, it's inexpensive and you can learn a lot
