Introduction: Using Gelatin for Moulds and Prosthetics

By Marshon
About: Untidy, disorganised and a bit silly. I am a photographer, artist, body artist, sculptor, prosthetic maker, model engineer, and general idiot who likes making stuff and messing about. I give hands on workshops…

After my 'ible regarding using alginate as a mould making material, there were lots of questions about materials and obtaining them. Here's another method that uses only items that are readily available.

Gelatin is a much disregarded product when it comes to the home user.
It is safe to use and has some fantastic properties, it can be cast, or used to make moulds, it is re-usable (you just melt it back down) and best of all it's cheap and easy to get hold of.
It's safe (you can obviously eat it), but it's not just for cooking!

There are plenty of on-line tutorials on gelatin preparation for SFX, but they all call for some exotic ingredients. This 'ible uses only off the shelf stuff, but it works perfectly well.

You can store the prepared gelatin in the freezer for months, so make up a few batches and store them for future use.

In this Instructable we will prepare two types of gelatin mix, and look at their uses.


Step 1: The Basic Mix

We will need the following materials:

Gelatin, you want the crystal or powder type, not the sheets. This is available in the bakery section of your supermarket. Gelatin is an extract of beef so it's a natural product. It is used to 'set' various foods. Most notably Jelly (Jello), but it is found in lots of recipes. I use 'Dr Oetker', only because it's sold in Tescos.

Glycerine is a pure form of liquid syrup. Found at the drug store or pharmacy. Often used to sweeten kids medicines.

Liquid honey, or 'runny' honey. The stuff in a squeezy bottle will do fine.

Warm water, a plastic jug, some plastic cups, some stirring sticks (from the coffee shop), a small electric whisk. some washing up liquid, and access to a microwave oven

Step 2: Making the Basic 'goo'

The amounts are not too critical, but I generally use a small plastic cup as a measure.

1 part honey
1 part water
2 parts gelatin
2 parts glycerine

Fill one small cup with gelatin crystals and set to one side.

Take another small plastic cup and half fill it with warm water, add runny honey to top it off and give it a gentle stir to dissolve the honey. Pour the whole cup of honey into your plastic jug.
refill the plastic cup with glycerine and pour that into the jug as well.

Warm the jug in the microwave, on full power for 20 seconds and give the mixture a really good stir. You want the mix warm to hot but NOT BOILING.

Add the cup of gelatin to the jug and start stirring it, you want all the crystals to dissolve. Give the mix another 20 seconds in the microwave if the crystals won't dissolve. Keep stirring and heating as necessary to dissolve the gelatin and give a uniform colour and consistency. DON'T LET THE MIXTURE BOIL!

Step 3: Cool It All Down

Once the mix has become uniform and a sort of clear goldish brown colour, it's ready for cooling. Stick the jug in the fridge or the freezer and leave it for four hours.

The basic mix is now ready. It will take fairly rough treatment at this stage, so force a finger between the mix and the side of the jug and pull out the 'puck' of rubbery gelatin mix.

The pucks can be placed in a food bag and stored in the freezer until required. I make up a batch of 3 or 4 pucks at a time and store them.



Step 4: Using the Basic Mix

The basic mix has a number of properties. It is strong enough to take a fair bit of undercut, though not as strong as RTV rubber. It can be used to make moulds by simply warming it in the microwave until it becomes liquid, pour it over the pattern, allow it to cool and then remove the pattern.
It will cast almost any cold cure material such as resin or plaster, as long as the pattern can take the heat when pouring.

The basic mix also has a few other properties of interest. It has almost exactly the same mass and elasticity as natural muscle. Therefore it can be used to cast excellent prosthetics, you can use a plaster single mould, such as the ones used in my other 'ibles, or in a two part mould to create face masks and suchlike. These are described later in this 'ible.

Here is a link to the work of Peter Gaal (a true genius) using a latex bald cap and a gelatin 'nose' prosthetic to create an alien girl:

The work of Peter Gaal

Below is how to use it to make a simple mould. I have used the gelatin to cast a bolt to show the undercut it will take. The resin cast has retained the thread pattern.

Remember that resin heats up as it cures. Too big a piece and the heat will start to melt the gelatin.

Step 5: Foaming Gelatin

Now that we have the basic mix we can foam it to use instead of foamed latex. It is used in exactly the same manner as foamed latex, but does not require any sort of special baking or foaming agents.

Place a puck of the prepared gelatin into your plastic jug and gently re-heat it in the microwave until it becomes liquid. DON'T LET IT BOIL!

Give it a stir with a coffee stick to make sure it is nicely mixed. Then add two or three drops of washing up liquid to the jug.

Get your small electric whisk and starting on the lowest speed begin whisking the mixture. Once it has started to take air you can increase the speed. You want masses of tiny uniform bubbles. I whisked mine for around ten minutes until it had taken on about 3 times it's original size.

Put the jug in the freezer for four hours. Then pull out the large plug of foamed gelatin. It is very much softer and more pliable than the standard mix and will make really lightweight masks and prosthetics.

Step 6: To Make the Peter Gaal Nose

To make a two part mould prosthetic like the one in the Peter Gaal video, we need to make some moulds. If you want a mask to fit a specific person then you will need to cast their face (that's for another 'ible). Otherwise generic ones can be made using a glass head or similar.

I'm going to use my mannequin head as the face cast.

Using plasticine, plonk bits onto the face in roughly the areas that you want the final mask. Start smoothing out the bumps and joints with your fingers. The mask in the video is simple and effective to make, but you could make almost anything you want. Be careful in areas around the eyes and mouth because you will have to stick this on later and you don't want glue getting in your victims eyes.

Plasticine is oil based so for my final smoothing I use a bit of WD-40 on my fingers to blend out the edges. Once completed, we need to make a fence to hold back the plaster and give us a working area. I use more plasticine to build the fence up. Now I leave it for a while to have some tea and a smoke and let it all settle down a bit.

Step 7: Pour the Plaster

Once you are ready mix up some Plaster of Paris or casting plaster (I use Crystacal-R). Dental casting plaster is also good. If your head is made of plaster, then you need to add a mould release agent before starting on the negative mould. Use Vaseline or one of the silicone release sprays.

Plaster for casting is available at most art shops, or craft shops, or off the net. I ignore the fancy mixing formulae, two parts powder to one part water (by volume) will generally give good results every time. One cup of water to two of plaster. Start by getting a quick even layer of plaster all over the mask. If you use a brush be careful not to disturb the surface of the plasticine. I like the messy aspect of it all and get stuck in with my hands and fingers.

Once you have a base of plaster down, start slowly adding to the initial coat. If it all gets a bit out of hand, leave it for 20 minutes to set and then mix up some more plaster and add to the dried stuff. Slowly, slowly catchey monkey. You can add plaster bandage or scrim net to strengthen and support the plaster as you go. Eventually you want a mould at least 3/4" or 20mm thick.

Let the plaster dry for an hour. Another cup of tea and another smoke helps here.

After an hour you can de-mould. Start by pulling away the fence. this will leave a ledge around the upper plaster mould. Grip the edge with your fingers and gently ease the upper cast off the head. It doesn't matter if some of the plasticine comes away with the cast or stays stuck to the head.

Carefully clean away and remove ALL TRACES of the plasticine from both the head and the mould. When fitted back together this will leave a void into which will go our gelatin. Congratulations, you have just made a two part mould.

Step 8: Casting the Gelatin

We now have a head (the positive mould), and a mask cast (the negative mould).

The method here is to heat up our prepared gelatin in the microwave until it is liquid (don't let it boil). You can use the raw or the foamed mixes. I would recommend that for this small mask you use the raw stuff, for larger masks and prosthetics try the foamed. Once the gelatin is melted in your jug (remember not to boil it), you are ready to pour.

Turn the negative mould on it's back so that the void is uppermost. Pour in the gelatin mix until the void is full, this will be more than the void needs so remember to do this where any spilled gelatin can be easily cleaned off and reused. I use a board covered in melamine (an old white kitchen cupboard door).

With the negative mould on its back, place the positive mould into the void and press the two together FIRMLY. Be careful since hot gelatin mix is liable to be squeezed out of the mould, you don't want the hot stuff all over your hands!
Force the two parts of the mould together gently but firmly until the positive and negative moulds fit snugly back together. I wrap some insulating tape around them at this stage to hold them in place.

You can either leave this arrangement overnight at room temperature to cure, or place it in the fridge if it will fit. Four hours in the fridge or overnight should ensure that the gelatin has set. Open the moulds gently and peel out your mask. If you are careful the moulds should make more than one mask.

The mask can be used immediately or chucked in the freezer for storage. Once you are bored with the mask, give a rinse to get any make up or paint off and then just melt it back down in the microwave and make summat else with it.

Step 9: Colouring

Gelatin prosthetics will take normal make up, face paint or body paint well. Here I have added some normal liquid foundation and some powder to one side of the nose piece.

If your prosthetics have well feathered edges then you should be able to get a seamless blend. Use a little witchazel to dissolve away the edges.

Gelatin requires either Spirit Gum or Pros-Aide as an attachment glue.