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Epoxy and Inlay

I’m in the process of doing some opal inlay into silver pieces. I’m
happy to report that, for my first attempt, the pieces turned out
quite well. However, I dismantled them because I didn’t’ care for the
state of “hardness” achieved by the epoxy. The epoxy that I used on
these pieces was a double trigger-fed, marine, black hardener with
clear resin, long-curing (1 week) epoxy. The working time on this
glue is 1 hour, much longer than your ususal run-of-the-mill 5 or 10
minute epoxies. I’ve read that for inlay, the long-curing ones are
best. Problem is, even after a week of curing, the epoxy never
hardened to the “rock hard” just became like a “hard
rubber.” Does anyone have a fair amount of experience with opal
inlay, and could you give me a brand or type of epoxy that will cure
to the harder state that I seek? Obviously, the harder the epoxy,
the higher polish I can get on it. Thanks for any tips.

Cathy Flory

Dear Cathy,

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)

Martin Niemeijer
N design
compositions in precious metal
Rieteweg 10, 8041 AK, Zwolle

I do intarsia using all sorts of stones, including opal. I’ve had
good experience with Hxtal epoxy, which is extremely slow curing. If
you Google it, you’ll find detrailed and suppliers. I’ve
gotten mine from

Susan Sanders