4 Ways of Creating Custom Rubber Molds (Halloween Skull Edition!)

If you have seen/read my other tutorials, you know that I love to work with resin. I usually use silicone cupcake baking molds to make jewelry, or I paint resin onto an object itself. Not surprisingly, there isn't a big variety of 3D molds to use with resin. I went on a mold making spree, and this instructble is a collection of my advice!

This is a remix/addition to an Instructable tutorial!

World's Easiest Silicone Mold

PS. If you want a mold that is food-safe (FDA approved), jump to step 4! Perfect for chocolate molds or sugar skulls.

Step 1: #1 - Liquid Latex

This is the product I used for this option in mold building.

I found it at AC Moore, but it is available from many suppliers online.

This instructable may be of particularly good use for those of you want to try this product! I was still very confused about how exactly Liquid Latex would work even after reading the instructions on the label. It's incredibly unique compared to the other methods of mold making I am familiar with, but that also makes it useful for certain projects!

Original Object

The original object that you are modeling has a few restrictions. It must be non-porous or sealed with a resin spray of some kind before you begin the liquid latex process. It is also supposed to be sealed if it is brass, and I am not totally sure why but I'm sure some type of chemical reaction ruins brass when it comes into contact with the latex.

The size of the object just depends on your patience I suppose. The photos or videos I have seen of liquid latex molds are of relatively flat objects, like a button or a charm. This made me a little nervous to try it on my Skull figurine. At the end of the day it just takes a lot longer to make a mold if your object is more 3D.

Basic Process

Make sure your object is free of dust and dirt (this applies to every type of mold making you try) and place it on top of a piece of wax paper in a position that has a flat part of the object resting against the paper.

Take a throw away paint brush or two (I ruined quite a few on my first try), and a clean cup of water.

Note before you open the container: This stuff smells terrible. Kind of like sulfur.

Put on rubber gloves and paint a *thin* layer on top of your object. Paint another thin layer around the object onto the wax paper. This will allow you to peal off the mold with ease when you are finished. Allow this layer to dry completely. You will know that it is dry by the color/opaque appearance. When the mold is not dry it will show a pure white opaque color. When it is completely dry it is yellowish and see through. Note: THIS IS VERY IMPORTANT.

After the first layer is dry, apply a second and wait for it to dry. Repeat this at the very least 8 times. If your object is more 3D, you should add as many layers as you have the patience for. The more layers, the sturdier the mold. I ripped the latex mold I made for this tutorial when I removed the resin replica because I only did 10 layers.

It takes about 5-10 minutes for each layer to dry. I would recommend doing this in-between other tasks, revisiting it to apply another layer when you get the free moment. It was very frustrating to sit in the stinky room watching the latex dry.

Finished Mold

Once you are satisfied with the thickness of the mold, and you have waited around 24 hours after the last layer, peel the rubber away from your original object. You really have to yank at it to remove it the first time. Latex is stretchy so it is fine to pull! Just remember that the mold is pretty thin.

To make my replica, I positioned the mold with the open facing up at the bottom of a plastic cup. I had to attach the flaps of the bottom of the mold to the sides of the cup so that the shape of the skull's head wasn't warped by resting on the bottom surface of the cup.

If you want instructions on how to use resin to make a replica, look at my other tutorial here.

For my mold, I used a brass original object and it had a reaction with the latex. It kind of left a stain of rust on the interior of the mold that I couldn't remove. Because of the stain, the resin replicas also exhibited a stain. I will probably end up just painting over it.

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PROS

Detailed Mold

Customizable size

No need for special mold making box

CONS

Time consuming

smelly

Fragile

Staining

Step 2: #2 - Pink 2 Part Mixture

This is the method that I favor over alllll of the others. The reasons are that the resin replicas it produces are incredibly smooth and detailed. The molds also turn out durable.

This one is simple!

Before you begin, create a sealed mold making box. I used a tin from a box of cookies, so I did not have to do any prep. If you don't have a tin grab some cardboard and use a hot glue gun to make a box.

The two parts of the mold making kit are both liquid. Mix the two in a container that is non porous and disposable. I used a takeout bowl from chinese food. Mix the liquids to the point that it is one continuous color (pink!).

Place your objects in the bottom of the mold making box. Whichever surface of your object is the flattest should rest on the bottom.

Pour the pink mixture over the objects. Pour enough mixture to cover the top of your object by approx 1/2 inch. The hard part is done. Congrats! Now you have to wait for 24 hours for the mold to cure. After that time period is done, remove your original object and you are all set to use the mold.

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PROS

Very detailed

Sturdy

Great for any shape object (2D or 3D)

Incredibly smooth resin replicas

CONS

Expensive (for the amount/size of molds you can make)

You basically have to make all of it at once. It is a one to one ratio, but the two parts are so sticky and runny I cannot imagine measuring out parts.

That being said, messy. I wouldn't let your 10 year old kid do this.

Have to prepare a sealed and disposable box to make mold.

Step 3: #3 - Silicone Caulk (Remix!)

ORIGINAL INSTRUCTABLE

This is one of the first instructables I actually tried! To be honest, mine did not turn out well for a multitude of reasons, the biggest one being I did not buy near enough caulk.

For that reason, I will give you some extra advice about the precautions to take when you do this project!

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First and foremost WEAR GLOVES. THIS IS IMPORTANT. Silicone burns skin when it is not solidified. You will regret it if you do not protect your hands.

Secondly, buy more silicone than you think you need. My attempt at this was ruined because I didn't have enough caulk.

Use a TON of dish soap. I coated my gloved hands in the stuff before picking up the ball of silicone. It is very sticky (like melted caramel stuck to your shoe) if you don't do this.

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PROS

Can make LARGE molds (Unique in this sense)

Great for 3D objects

$ Cheap, Cheap, Cheap $

CONS

Smelly

Need to make sealed box for mold

Can burn your hands (see precautions above)

Hard to estimate how much silicone caulk you will need

Difficult to ensure your mold is free of leaks (found this out the hard way)

Step 4: #4 Purple 2 Part Mixture

Product Used

This mold turned out sturdy and detailed enough for my purposes. It was also the easiest to make!

The instructions are basically as simple as the box puts it - blend, form and use.

Measure

Before you blend the two components, you have to measure out equal parts either by volume or by weight. I chose to do this by weight with a simple kitchen scale. It is much much easier to get exactly equal parts doing this by weight, but if you don't have a scale use a plastic cup and smash down each part (separately) to the same level to measure it out by volume.

I used 1 oz of each substance.

Blend

Combine the white and purple parts in your hands, kneading them like dough. Do this until you have a single continuous color (no white or dark purple streaks visible). Once you get to this point, its time to make the mold, but be quick because you only have 3 minutes to do it. The clay cures rapidly.

I put on gloves for this part because I didn't want my hands to smell or get sticky, but its not necessary!

Form

Make the mixed putty into a sphere/ball. Set the object you wish to make into a mold on a flat surface (non porous). push the ball onto the object and squeeze it all around the sides. It's pretty self explanatory. Make sure you form it around the object tightly enough to pick up the details.

The putty should have a thickness... actually I don't know the measurement but I did it by feel. Just make sure when you press on the putty surrounding the object you cannot feel the hardness of the object immediately. You want it to be thick enough to remain sturdy throughout use, and to be free of leaks or holes.

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