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Resin grinding


#1

Hi Everyone-

I experimented with resin for a special project and I wondered if
anyone was familiar with what the last “grinding” step entails? I
want to keep the high polish of the colored surface ( sometimes) and
the usual sanding step leaves behind a cloudy, transparent ( not
tranlucent) effect. Also if you could possibly suggest a two part
adhesive that does not (hopefully ever) turn yellow with age? Your
help is greatly appreciated.

Thanks very much!
Adriane


#2

We used a watercooled flat lap grinder to finish our pieces in Karen
Christian’s workshop, followed by a coat of Krylon clear acrylic.
According to Karen’s testing, the Devcon 20 minute did not yellow as
it aged.

Chris


#3

Adriane, I recently was trying to discover this myself, and was told
to get plastic polish from a store that sells car finishing stuff
(like Auto Zone). I haven’t tried it yet, but I’ve seen that as the
way to do it in a couple of places since, including a resin jewelry
making book I got from the library last week.

Jen
http://www.jmwjewelry.com


#4

The flat lap grinder is from Ameritool and is called The Universal
Grinder.

http://www.ameritool-inc.com/

They are very nice people to work with and the grinder is a joy and
workhorse. I first use a 110 diamond disk and ordered extra back
plates from Ameritool. For the additional abrasives, Rio has the 3M
Diamond Micro Finishing Discs, abrasive mesh at 220 - 600. They are a
bit pricey for each pad, but they last quite a long time. The heavy
diamond disk really does the major amount of grinding work.

For sealing the epoxy, there are several options available. Krylon
used to make only one type of matt sealer that dried in minutes. They
now have a longer cure which dries in two hours. Rustoleum has now
come out with a longer cure matt spray sealant which is very good
with brass, copper and silver.

Take note that there are two kinds of spray finishes. Although they
are both acrylic, one produces a shiny and reflective finish and the
other is non-reflective in a matt finish. My preference is the matt
as it absorbs light and pops the color of the organic materials I use
in my work.

Tips on grinding. The 110 diamond disc is amazing for chewing down
epoxy, but it is also excellent at chewing your fingers. If you are
grinding a brooch, make sure of course that your pin backs are
secured by soldering first. A rubber eraser stuck into the pin backs
are great little holders.

For the tiny parts, I use cardboard with a piece of double sided
sticky tape which will hold the tiny metal part with the epoxy quite
nicely. Be sure to regulate the water dripping so it has enough to
keep the disk wet, but not so wet that you are creating a mini
tsunami.

I grind everything first with the diamond disk, and then quickly run
through the other abrasives. The last and final polish is beautiful
and the grinder is quite a time saver from sanding everything by
hand.

Good luck!

Karen Christians
Cleverwerx


#5

Adriane:

I used to do a lot of champlive work with resins. It was all ground
and then re-polished. The only ‘trick’ I found was (A) I built
myself a slow-speed flat lap machine, and (B) lots, and lots of
patience. You can polish it with zam, with a couple of things in
mind. First, your sanding must be immaculate. Normally, on metal, you
can go from 220, straight up to 400, then hop onto the buffs right
from there. Not a hope with resin. The scratches won’t ‘flow’ closed.
They’ll just stay there, lurking, until you go to do a final polish,
and then discover that you’re going to have to go all the way back
down to 320 grit to get them out.

So, sand with 320, then cross that with 400, cross that with 600,
and then start buffing. I tended to use felt buffs. (but then
again, I was doing flat surfaces.) The little teeny felt buffs that
are combo’d with felt inside ring spikes seemed to work pretty well:
too small to build much heat.

First compound was usually English Tripoli. (Bought in Hatton Garden.
Dunno what the difference is between the tripoli here in the states,
but there is a slight difference.)

Follow that up with a soft 3-4" buff with zam on it, and final
polish with a soft flannel buff with nothing at all on it. I have
some specialized plastic compounds that I played with towards the end
of when I was doing that sort of work. Some of them worked well,
some, not so much. The best of them was something I got from Vigor
for polishing plastic watch crystals. (Don’t remember the name, but
it’s a small, pumice colored stick. (No, not made pumice, just that
sort of dirty brown color.))

The biggest issue is heat. If you let the piece heat up, the resin
will melt and smear, and then you’re toast. Keep the buffs slow and
cool. Make sure all of your coarser scratches are out before you
switch to the next higher grade of paper. Resin has no forgiveness.

FWIW.
Brian.