Instructables
Picture of 2-part brush-on silicone mold

This Instructable will walk you through the process of creating a 2-part brush-on mold of an original.

2-part brush-on molds are ideal for replicating complex shapes that would otherwise be impossible with a pour (block) mold or glove mold. Using a brush-on technique gives the silicone more flex when demolding and require less silicone than pour molds. Splitting the mold into two parts can allow you to work around undercuts in a mold.

Note that you can add more than one mold part line, however this will increase the complexity of your mold.

In this Instructable I will be making a mold of a clay original that I sculpted and then creating a slush casting using the mold.

Materials I used include:

  • non-sulfur oil based clay (6 lbs)
  • clay tools
  • dragon skin 20 silicone (2x trial kits)
  • plasti paste mothermold
  • mixing containers (x20)
  • brushes (x2)
  • stirring sticks (x20)
  • gloves (a lot)
  • smoothcast 300 (1x trial kit)
  • mold release
  • wing nuts
  • 1/8th MDF board
  • sewing tape measure

Step 1: Create design

Picture of Create design

Start by designing your part.

I had a mannequin head around, so I thought it would be fun to make up some sort of futuristic spacesuit helmet.

The first step is preparing the base model for fabrication. If you're using a base model that you don't want to get ruined with clay or mold material it might be a good idea to cover the model in something silicone friendly (note that silicone has a hard time curing on certain material surfaces). I covered mine in plastic wrap and tape.

The mannequin head was obviously not to human scale and I wanted the helmet to fit my head. So I found my head measurements using a sewing tape measure then, added clay to the mannequin's head until it matched my measurements.

Next I sketched possible designs over a template. I included the template file I used.

Once I drew something I liked I started building and used the drawings to inform what I made.

It might be helpful to draw these at full scale so you can compare what you make directly to the drawings.

 
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coloso242 months ago

Hola gentes, yo estoy empezando en estos y los materiales me suenan un poco a chino, con la arcilla a base de aceite hacemos el busto, y cuales son los otros materiales a usar? silicona liquida para que cree el molde y luego que es lo que le echa para que solidifique y haga las caras solidas? y luego al interior, para hacer el casco en si que utilizais? Estoy viendo que algunos ingredientes no son nada de faciles de encontrar.Gracias a todos.

Arcilla a base de aceite = plastelina

los demás son nombres comerciales

May i suggest the use of 'Dividers' as pictured to make sure the model is symmetrical?

Other than that it is a very very good instructable and answered a couple of questions I have wondered about.Love it! Favourited!

201100_xl.jpgdividers.jpg
rlciavar (author)  HappyToBeAlive2 months ago

Making the mold symmetrical would have saved me a lot of trouble getting the profile for the mothermold part line right!

padbravo2 months ago

And in a few years, this will be a forgotten art... the new generations will push the "print 3d" button, and voila!

rlciavar (author)  padbravo2 months ago

Haha 3D printing is always an option but sometimes the best part isn't the final product, it's making it yourself!

fluffydragon2 months ago

This is a really great instruction set, thanks for writing it up. Did I miss a part where the clay dries out before making the partline? or does it dry completely?

rlciavar (author)  fluffydragon2 months ago

The clay is oil based and never dries out. You can keep reusing it after each sculpt. I've had some oil based clay for years.

The Rambler2 months ago

The more I read about this process the more confident I get that I could actually do this. I like to read about a process from multiple sources and get different people's takes on it before trying it myself. I feel like I get a better idea of what's it's actually like. So thanks for posting this. Before I try it I'll definitely be referring back here again.

rlciavar (author)  The Rambler2 months ago

That's the same approach I took before making my first mold. Post pictures when you try it out!

varenzaa2 months ago

Wow! Nice idea! It is new knowledge for me. I get inspired from this post.

poofrabbit2 months ago

This turned out wonderful! Great instructions with easy to follow pictures, I feel confident I could do this given the time and may have to try for this Halloween! Thanks so much!

rlciavar (author)  poofrabbit2 months ago

Glad you enjoyed it! post pictures when you try it out, it's lots of fun!