Saturday, 28 January 2017

Making A Multi Cavity Silicone Soap Mould

Project: Making a multiple cavity (Egyptian) silicone soap mould.


RTV Silicone/catalyst -  or you could use a Latex rubber moulding compound which I do in my next post.

Bathroom heat lamp globe (sold in supermarkets for under $15) which is used to soften modelling compounds and to provide even heating for the silicone mould once it is finished.

Modelling compounds - Plasticene, heated with the heat lamp for a couple of minutes;
Fimo oven bake clay - the Chinese variety, commonly found on Ebay under 'oven bake clay' or 'polymer clay' (The cheaper the better because the cheaper ones are harder and less pliable).

Cheap thin paintbrush, from a child's set or similar.

Cheap pourable craft glue, from discount stores.

Offcut of a tile, glass sheet or perspex, or anything else with a smooth, flat finish.

Egyptian positive object/s, with flat bottoms. You can use anything else you like to make an embed, as long as the underside is flat. Jewellery pendants, charms and buttons are examples.


First, I secured my Egyptian positive objects to a long piece of perspex offcut using craft grade glue (found in discount stores). I used the cheap paintbrush to brush the glue all over the back of the positive object, with the glue being thicker in the middle. The sheet of perspex then went under the heat lamp for 30 minutes, to set the glue.

Once the objects were glued onto the perspex firmly, I then backfilled any protruding undercuts underneath each positive, using warmed plasticene and poked the warm plasticene around using the non paintbrush end of the paintbrush. The perspex was then placed onto a piece of wood which was levelled using a spirit level. Although it looks like the positive objects are sitting on a wooden base, they are sitting on the clear acrylic perspex. 

Next, I built the mould walls and borders around the perspex base. I used the cheap and nasty 'oven bake clay/polymer clay' which I cut in long strips about 1 cm high. 
 I then used softened plasticene to build a softer wall on top of the polymer clay and filled in any gaps along the bottoms and made sure there were no gaps on the inside or the outside of the mould. I did not bake the 'polymer' clay in the oven for the bottom still needs to be soft enough to adhere to the perspex and plasticene. Using the other end of the paintbrush, I poked and prodded the warm plasticene around until I was happy there were no gaps. Now it is ready for pouring silicone into, to make the mould. 

The positive Egyptian objects adhered to perspex, with the wall of modelling clay and plasticene now complete.

Now with the mould walls secured around the perspex, I poured the silicone into the mould and turned the heat lamp towards the mould once it was finished.

One polymer clay strip on the bottom layer, with softer plasticene moulded onto the upper layer.
Finished silicone multi cavity embed mould
As it is a mild summer evening, I will leave the heat lamp on overnight to ensure the temperature of the silicone constantly stays at around 23 degrees. I can soon smell the familiar smell of the catalyst warming the silicone, which is a good sign. Within 48 hours my mould should be cured and ready to demould.

Thank you for reading my blog about my serious silicone moulding addiction :)