notes are given in good faith for general guidance purposes
and since actual operating conditions, methods and
techniques are beyond our control we cannot accept
for any losses however they may occur. Other help sheets & tips are available via the
instructions & guides link above.
General notes on
small resin castings.
Mould release notes HERE
For optimum clarity air bubbles introduced when catalysing need to escape
quickly so warm the resin first to 25ºC, then add a small amount of
catalyst say 1 to 1½% (note it down) mix in thoroughly and pour into
mould, If air evacuation fails to be complete when gelled, then adjust
next mix via resin temperature (upwards) and slight reduction in catalyst
to allow longer working time.
Castings can be pigmented and/or filled but these basic rules should be
Resin can have up to 10% content of pigment (parts by weight) and must
have this introduced BEFORE any mineral powders or required catalyst
The maximum of talc or similar introduced is governed by its absorption
value having direct effect on the resin mix viscosity, if too sticky then
vacuum equipment may be needed to successfully de-air.
A significant benefit of filler powder is that of being an inexpensive
extender and its effect when in a resin matrix is of lowering peak
exotherm temperatures which lessens thermal shock and so enables larger
volume castings to be made.
Our general purpose resin is OK for small castings and those of up to 50cc
providing good results with tack free finishes and average 5% shrinkage.
When catalyst reacts with resin a heat generating or exothermic reaction
occurs making the casting hot when gelling and entering the cure stage.
Too much catalyst or high working temperature or large resin mass can each
result in a very high exotherm, inducing internal stresses that can lead
to high shrinkage and fracturing.
With practice however larger castings can be achieved by careful technique
and where necessary casting in stages allowing each to set first and pass
its peak exotherm.
Polyester resin is in itself brittle when set and has little tensile
Larger castings should be reinforced with chopped strands or some
It is important the casting is sufficiently cured before buffing/polishing
and elevated storage temperatures speed this up, if under-cured it will
fail to polish to a gloss.
DO NOT attempt to wipe cured castings with acetone, it will soften the
surface and leave it dull.
Proprietary metal abrasives/polishes (Brasso type) have given good
These notes are given in good faith
for general guidance purposes
only and since actual operating conditions, methods and
application techniques are beyond our control we cannot accept