The old grey matter

I've decided it might be a good idea to have a back up plan, just in case the glass casting doesn't go awell as expected, so I'm going to make a positive mould that will allow me to repeat the process without several of the steps.

To do this I have set up the plaster moulds as they would be for accepting the glass.  Instead of glass I am going to use a silicon rubber mix.  I'll be using a Tiranti solution which is a two part mix; the base is Tiranti T28 and the catalyst is T6 to a mix of 20:1 (or 5%) using a weight measure rather than a liquid volume measure. I will also use an Alchemie R5 release agent which is sprayed in two coats over the surfaces of the plaster cast to help remove the silicone once set.

Measure the compounds accurately,  I need 600gms of base and 30gms of catalyst, and mix them very well together.  This catalyst is clear which makes it difficult to see if the compounds are fully mixed, some compounds are coloured which makes this stage a lot easier. 

Mixing will fold in a lot of air so sit the mixture aside for a few minutes to allow the air to bubble up to the surface.  In the meantime inspect your plaster moulds to make sure they are thoroughly clean.  Once everything is clean and the bubbles have cleared out of the mix it is time to pour.

Pour into the mould slowly, allowing the compound to gently rolled over the contours of your mould which will stop any air being trapped and bubbles forming in your end mould.  When the pour is finished tap the sides of the mould and bang the table top many times as this will encourage trapped air to bubble up and release.

Now let it set.  This particular mix will be set in about 6 - 8 hours but will finish curing up to 24 hours.  Leave your mixing jug and spoon alongside your mould because once it is dry then the mix inside the bowl will be too.  You can then just pull out the spatula and the whole mix should come in s singular piece.