When I got home last night I tried to use a piece of glass to give my casting a FLAT base, it did NOT go well....!
Using my big open topped block mold, given a little shrinkage in the resin, yields very thin edges where the original sculpt tapers down to "ground" level. To try and reduce this effect I sprayed a bright, shiny, NEW piece of glass with silicon lubricant thinking that would let me just slide the resin casting off and have a wonderfully smooth bottom.
To my dismay and GREAT irritation, the resin clung to the glass and wouldn't even consider letting go.
I managed to slice a chunk of skin off the back of my middle finger on the edge of the glass... Ouchy!! And this not even a minute after saying "I know I'm going to hurt myself doing this..."
And then, just to be mean, while cooling, the resin shrank and cracked the glass into 8 or 10 pieces...
But amazingly, the glass was still adhered to the resin! I ended up smashing the glass into tiny bits and still some is attached to the resin!! I have even dragged it along a concrete sidewalk and all that did was smooth out most of the sharp glass edges....
Needless to say, that cast is ruined and useless!
I might be able to salvage it as a painted example...
The gooey part of the mold had not completely cured so I cut into the side of the mold and scrubbed out the unset silicon and refilled the cavity with a new batch. That fixed two separate spots, but I discovered this morning that it did not fix the one that was causing a serious problem in the finished pieces (right where models would be placed!).
I did a little more surgery this morning before leaving for work and I hope that solves the problem, if not I'll have to remake this mold and lose probably $30 in materials! If the mold comes out usable, I plan to turn it into a two part mold that will give it a little more thickness at the taper points and pour it from a side. If I go this route I am going figure out a way to have my name and the copyright symbol integrated into the mold so it comes out on all the finished casts.