thanks Iain, good reference material is a definite must
yeah, different ratios of hardener:resin will give properties, as well as mixing different putties
for instance, on the commander the brownish puttie is a mix of the brown(BS) and yellow(GS) resins and white hardener(BS) ie (Y:B):W, it dry\'s hard like brown stuff(BS), but with some of the flexability of green stuff(GS)