World's easiest silicone mold.

Yep. That's right. I am about to change your mold-making technique forever. This simple way of silicone mold-making will have you wanting to make casts of all your trinkets and toys.

You will need:

• water
• blue dish-soap (any brand seems to work)
• silicone caulking (do not buy quick set silicone, you need 100% silicone)
• bowl
• caulking gun
• something you want to make a mold of.
• scissors/knife
• masking tape - to patch holes in your positive, if necessary.

Step 1: Make your catalyzing solution.

By mixing a high-concentration of dish soap with water in a bowl, one is actually making a catalytic bath for your silicone. The glycerine in the dish soap accelerates the cure process for of your 100% pure silicone.

This is by no means an exact science, I use blue dish soap because it allows me to see how much I have added to a water bath, I approximate that I used 4 oz. of soap in 64 oz. of water.

Step 2: Catalyzing the silicone.

Cut off the tip of the silicone caulk tube, and set it in the caulking gun. Unload enough silicone to surround the desired object, into the bath.

I use the whole tube usually.

Step 3: Preparing the silicone.

While keeping your hand submerged in the dish-soap catalyzing bath, gently clump the string of silicone together. Form it into a ball, and slowly massage it. Fold it, stretch it out, and work it very much like one would knead dough.

When it begins to become a bit less malleable, and stiffen, it is time to sink your positive into your material. In this case, Mike helped me, and we used his dinosaur, Jesus. (hay-zoos)

Step 4: Make sure the mold is water tight.

The best way to make sure your mold is watertight is to add a kind of thick-ish layer of silicone to the surface area of your object. Note how the dinosaur is padded by about a 1/2" layer of silicone all around its body. Also, I have left a considerable amount of the dinosaur uncovered, as I am only casting half of this figure.

You want to make sure you can still wiggle your figure out of your mold, without any of it getting caught, otherwise it can be very tricky to extract once your mold has set.

Step 5: Let it cure.

It will take about an hour for a full cure of your mold, before you can use it. Allow your object to remain in the mold while it cures. When the mold is no longer tacky to the touch, and feels rigid, gently remove your positive.

We kept this mold on top of the fridge, and put a bit of soapy water down on the plate so that the silicone didn't meld with the paper plate.

Also, this part smells awful. Make sure you do all this in a well-ventilated space.

Step 6: Use your mold!

We made a sparkly rendition of Jesus with clear casting resin and glitter. When the resin began to gel we set three LEDs inside of him. Behold the sparkliest light up dinosaur in West!

Comments

[Kimtt]

I did all the steps, but after I tried to take the resin out after it had 'cured' it was sticky and left bits in the mold. Is there something I'm doing wrong?

[audreyobscura]

Ah. Your mold is probably perfect - It sounds like you didnt add enough catalyst to your resin. Or you could have cured it in a room that is too hot. Resin is very finicky stuff.

[cbernards leiberan-titus]

This is so awesome! Thank you so much for sharing these instructions. :)
Do you think the mold could go in the oven, like silicone baking products? I was thinking this would be awesome for making custom crayon molds.... but I don't want to kill myself with off-gassing or chemicals.... Thank you, this looks like such an awesome idea!

[stayputnik]

Silicone generally is heat safe up to about 500 degrees F (give or take). If the stuff you're using is genuinely 100% silicone, it should be fine in the oven... especially at the temperatures needed to melt crayons. Might want to open a window just to be safe. :-) Let us know how it goes!

[Dark Light]

This is neat! Caulking isn't just for bathtubs anymore. lol. Thanks for posting this...I'm sure I'll get some use out of it.

[gserrano701]

Great work, saved the PDF for future use. I made some oogoo once with red silicone (heat resistant for engine seals) and talc, only a small job and it worked great once I added the right amount of talc. Have to try water as a catalist. Thanks.

[theswamplady]

If red silicone is heat resistant could it be substituted for the clear and then fired in and thus create a mold that could be used in an oven at 400 deg? Debbie N

[paqrat]

This is way cool. Have you tried it with the white silicone caulk?

[cthulhulovesme]

I have. It... didn't end well. The pigment in it felt like it was burning my hands after I started pulling it out of the soapy water. I'd stick to using the clear.

[jaybo2099]

It needs to be 100% Silicone caulk, aka "the clear stuff". Most of the other Silicone's actually have latex and other additives mixed in and don't work well at all. Plus, they are more expensive.

[Broom]

That's important enough you should mention it in the 'ible itself!

[paqrat]

Back when I had aquariums there were some folks making their own aquariums and someone said you didn't want to use some of the bathtube silicone caulk cause they have some sort of fungicide in them to prevent mold in the caulk. That may be what you felt on your hands.

[stringstretcher]

Rubber gloves... problem solved!

[paqrat]

Rubber gloves wouldn't stick to the silicone caulk?

[cthulhulovesme]

I've had issues with the silicone sticking to gloves and generally becoming a huge mess. I suppose "huge mess" is better than, "it burns!", but I always preferred the greater dexterity.

[stringstretcher]

Absolutely. These are chemicals. Soap removes the protective layer of oil on your skin, allowing the chemicals to penetrate your skin and cause potential harm, perhaps including nerve damage. I worked every with silicones for ten years, and have been given this info as professional training. Please, protect yourself. I know that sounds like your mother... there has to be a better way!

[audreyobscura]

I haven't - if you try it let me know how it goes!

[studleylee]

AudreyObscura(CoolName!): To add to your great guide: A neat trick I found online a few years ago, is to add a few drops of Acrylic(!) hobby paint( about 2-3drops per dixie cup of silicone caulk ) and mix well. The Acrylic paint also acts like a nice colorant and mix indicator, but it's water contents causes the silicone to cure solid throughout the mold like regular 2part molding compounds. I think this is what the soap is also doing.

I've used this to make custom insulators and rubber-Sugru-like items. If you want a courser texture add a little cornstarch. -Lee Studley

[paqrat]

I think I have some white silicone tub caulk. I'll check it out and may try it this Sunday.

[paqrat]

Turns out what I have is latex. I'll try picking some up though next time I hit the store. I think I'll stick with the clear though.

[jlyvers743]

You made a great instructable. Some one commented that a demo making and registering the other half of the mould would be helpful, I agree, I would like to understand that part. Just an FYI, they sell strait glycerine in the pharmacy area of most drug stores. I purchased a huge bottle for around$14. You would need to use as much of this as dish soap because dish soap actually has a very small percentage of glycerine. A drop or two of food coloring would give you that blue you like. It may be cheaper than soap but if your only doing a few items I dont know that it would be worth the change. Thank you again for this great instructable.

[maggieelrod]

I love this idea but really want to figure out how to make a very large mold ( with both sides, so it can be put together) of a large urn. Does anyone have any ides?

[fjordcarver]

Mix cement or grout with silicone to make aquarium safe, textured models. You have to leach them (soak, dump, soak, dump) to make sure they don't interfere with ph balance if they are going in a water tank. For a terrarium I wouldn't bother, but let them cure well.
It is water that accelerates the curing. water in corn starch or grout. (which is why in recipes for both these agents, you start with a certain amount of water too add and then add accordingly until mixture is right, depending mainly on air humidity and how much is already absorbed)
The soap releases, which is why it works way better than spit for going around a tub(spit works too, but silicone unavoidably sticks to your fingers and makes a mess eventually)

[fjordcarver]

I just found this because you tried my little app (or someone typed your name in), and because in your stats it was third most popular. I am really glad I found this. Double huzzah, because you tried my app, (another editor...triple huzzah). So thank you for both, ('ible and visit)
I can't wait to try this out. So cool. A liitle dish of water and dishsoap is great to smooth the joints when caulking around a shower or tub too.

Silicone is awesome stuff.

[FrozenIce]

a dinosaur called Jesus, aint that ironic!

[fireguard]

Nice project! I've wondered about this often, and my question is: What kind of casting resin/did it come from a "Hobby shop?"
Radioactive T-Rex... my boy would be geeked for that!

[spark master]

this is very cool, but the thingie would be more viewable in a solid color not clear. Can you do one in color so we can see just how perfect Mr. Teeth is?

[codongolev]

do you knead it in or out of the bath?

[audreyobscura]

both, i mostly knead it while submerged, but pull it out every once in a while to see the surface of the silicone, and squish it to se how it responds.

[kcbirder]

This looks very cool. Thanks for posting. I'm most interested in making molds for polymer clay, and I have a few questions.

Since I'll be working with smaller items, can you use smaller amounts of a tube of caulk and close it again? Could you use something like this instead? : http://www.dap.com/product_details.aspx?BrandID=67&SubcatID=27

And, once silicone is cured, could you bake the mold with the clay in it? Polymer clay is baked at 275F for half an hour. Will the silicone tolerate that?

Thanks for any insight!

[l8nite]

they use silicone for baking molds so it should be ok, but the only way to find out if using something in an unintended way is to try it. Silicone is still a little flexible when cured so I'm not sure the polymer clay would take a lot of detail unless you could liquify it somehow. Try it and let us know

[stringstretcher]

Most silicones have a max temp around 200C, I believe. Some will take higher temperatures, but silicone burns when exposed to high heat. Baking polymer clays should not be a problem, since you only go up to 150 C ? Do not try and bake foods in this kind of silicone, it is not made for that. There are others that are made for the food industry. Don't poison yourself :)

[allenamistral]

I would assume the detailing would be fine as long as your clay is properly conditioned. Most of the molds that they sell for polymer clay are flexible because you need a way of getting the uncured clay out of the mold (not sure if they're silicon or not). I've never baked a polymer clay mold, but I would assume that the silicon could withstand the temperatures because there's a lot of silicon cookware out there. I would not, however, bake it in an oven that you use to cook with. I don't know what else is in silicon caulking other than the silicon, but I can't imagine that it would be good to ingest.

[mediabeing]

Gee, I wish you'd shown us a standard casting so we could see if the mold really works [reproduces detail well]. Oh well. Maybe you'll do that next time. Yippeee!

[danzo321]

I know that this technique can give pretty high quality results, but here I see no t-rex teeth etc. You could lightly grease the object, squirt silicone I on it, and let it cure, and if using the clear, cut the mold with a sharp blade to free the pattern object. But you also should build a funnel in to the mold so you can get resin into it.

[Nirgal38]

If you look at the original images (by clicking on the little "i" in the upper left corner of the images), you can see the teeth. They don't show up in the smaller versions of the pictures because they aren't painted a contrasting color.

I've wondered if silicone caulk could be used to make molds and now I know that it can.

Awesome job!

[eschneck]

Thanks for the tip on the "i" Good Guy Nirgal38!

[gtoal]

Read the "oogoo" articles on Instructables. They'll show you how to use corn starch (aka Talc, as currently formulated) to cure the Type I silicon far faster.

[killbox]

The water is actually the catalyst, the soap pretty much works as mold release.

you can also do this with pure silicone caulking and a teaspoon of corn starch, (it too will quickly catalyze the silicone.

you can then soap cover your object and your hands and make a mold you only have about 5-10 minutes to work the stuff before it becomes too thick and rubbery.

[codongolev]

that's basically just oogoo, which is definitely great for molding. it'll stand up to the heat of molten solder if you feel like molding a metal lego or cow head (both of which I've done).