The top three image show the model embedded in white clay and ready for the first layer of silicone. I chose to use clay this time around on the basis of a video I saw on You Tube, and because neither plasticene nor blu tack had been satisfactory. The tank is tilted in order to facilitate pouring the resin without trapping air bubbles. This is the biggest mold I have attempted to date. When finished it will weight approx 1200gr, which with the price of RTV silicone in Denmark, comes to about £146.
Having poured the first layer, I compared it to the original maquette I made. Since it has the exact same dimensions, I could see the top of the model was only covered by about 5mm of silicone. This didn't seem much, though in theory it ought to suffice. I decided to play it safe and added another 200 gr of silicone.
This is the current state of affairs. The silicon has cured nicely (it is fantastic stuff), and I have removed the clay. It took about an hour but as the clay is water soluble, it was easy to remove without doing any perceivable damage to themodel, though it has stained it slightly. I shall give it another wash tomorrow before I pour the second layer.
Yours truly, now with full protection, and music whilst I work!