> The results have been satisfactory, but not of the crystal clear quality 
> of the "tombstones" produced by the deal lucite companies

"water clear" polyester generally has a blue tint. The resin itself may be
water clear but the promoter is often a metal salt and they are coloured.
The peroxide at some level reacts stoichiometrically with the promoter
and effectively de-colourises it. You know from basic chemistry that
metal salts of different valences have different colours. Similar thing. If
you under-catalyse, the resin retains the blue tint. Over-catalyse and it
may go a bit pink, depends on the reagents and how the promoter is
eventually bonded into the chains

> Some castings I made over 2 years ago are still slightly tacky on the surface

The styrene linking in polyester can be easily upset by other materials.
Surface oxygen and moisture are two. What I do with my castings is to
cover the exposed surface with a piece of laminating plastic (as you'd
find at a laminating shop). This excludes air and moisture and the surface
cures hard. Just about nothing that cures hard sticks to laminating plastic

I do use glass occassionally, but you have to have it scrupulously clean
and give it a good polished coat of carnauba or mould-release wax or
you'll end up with more pieces of glass than you started with

> I had read somewhere that using silicone molds for this type of resin
> can cause surface curing problems

Can't say I've had that problem too badly. Silicone should cure inertly. It
can be expensive for 'unimportant' jobs though. For re-useable moulds I
have meltable (180C) rubber that I melt on the stove in a pot in a sand
bath to buffer it from the element. Very handy for copying. I used it not
so long ago to make a mould of parts on one side of a plaster-cased
clock to repair chips on the other


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