Here are the things I've been working on lately :
Bases (30mm diameter with years inscribed on them for tournament trophies).
I have made a mold that prepares the bases for holding magnets (3 per base).
When I won't have a 'magnet back', I will try using a glass tile for the back.
Front (bases mold)
Back (magnet mold)
Assembled
The casted bases ! Which are : perfect !
I have tried Smooth On 300 and 305.
Both are perfect for my needs !
I created the mould with Smooth-On Mold Max 30.
I used vacuum and pressure to create the molds.
I casted the bases with Smooth-On Smooth Cast 300 with a pinch of black tint. (I will switch to Smooth Cast 320 with a pinch of black tint)
I only use pressure for casting the bases. A careful handling will get rid of bubbles : NOT pressing on the silicone back. And in a sandwich between two wood plancks and held by rubber bands.
I will post photos of the casting process !