Epoxy has a different way of curing than for instance polyester.
Polyester has a catalyst for hardening. This hardener let the
polyester strings join together. After this process the hardener
redundant. The hardener has to evaporate from the polyester but this
can take years. (it’s the polyester smell).
Epoxy works different the resin and the hardener are forming one
complete structure. In which the hardener is the laying between the
strings of resin. The more hardener the more flexible the epoxy will
be. The strings can bend easier with more space between them. Normally
about 50% hardener will give the maximum hardness. And with 1:1,
(resin:hardener) you get a rubber like plastic of about 80 shore
hardness. But this depends on the type and manufacturer of the epoxy.
Your problem is the use of to much hardener. Check out the
manufacturer and ask him for a table in which the hardness towards
the % hardens is given.
An other trick: Polishing epoxy is difficult. It is easier to paint
it with some epoxy after grinding filing to get it shining again.
Also spraying with a clear K2 car lacquer works well.
This lacquer you can also use for inlaying but than you have to ad
more layer. Spray some in a cup and let it degass for a minute and
than it is ready for use. ( this is also a kind of epoxy but very
hard and good to polish)
compositions in precious metal
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