Bob La Londe wrote:
"cavelamb" wrote in message
m...
Bob La Londe wrote:
With all the epoxy gurus here I thought I would ask a question.

Have any of you guys poured epoxy solids?

Encased things in epoxy?

My daughter said one of her friends said she wanted some paperweights
for Christmas with fish in them or fish shaped paperweights or
something like that. (Yes my daughter's friend is weird.) I thought
I might buy some toy fish at the local toy store or whereever I can
find something suitable and then pour them into some epoxy solids. I
figured a cube, a tetrahedron, and maybe a dome. Making a mold for a
sphere is not out of the question either, but I was thinking maybe
just a hemisphere for number three.

I can make molds out of wood or aluminum for the cube and
tetrahedron. For a sphere or hemisphere I would probably have to go
with wood.

I was thinking if I go with aluminum I would polish the interior
surfaces, put a tiny bit of clear RTV adhesive silicon in the seams
and spray the inside with non flavored cooking spray to prevent
sticking. Basically screw the pieces together. When the resin is
hard remove the screws and knock the sides off. Then cut the bottom
square and epoxy on a layer of felt. Any of you guys see any problems
with that approach?

For wood I was thinking I could make it similar to the aluminum, but
coat the wood pieces with epoxy first. Would take longer because I
would have to make sure the resin coating the wood was fully cured,
and thick enough to machine smooth for drilling and assembling the
mold. The advantage to wood is I could more easily make a sphere or
hemisphere shape, and it would be a lot cheaper than a piece of
aluminum thick enough to make a reasonable size sphere.

You have any tips?

Any Alternatives?

Reasons why my idea is totally stupid?

I have several gallons of two part epoxy left over from a previous
project.

I also considered milling some fish shapes out of wood and using them
in the "paperweights", but I am concerned that escaping air might
cause bubbles in the end solid. I suppose I could paint the shape
with epoxy before encasing it.



A better choice is acrylic casting resin for jobs like this.
It is generally crystal clear, but can be tinted or pigmented,
or filled with a filler (sand, marbles, keys...)

Any thickness (depth) of epoxy will likely go thermal on you and boil.

What about regular polyester resin? I might have enough on hand to do
one item?

Trying to do this with stuff on hand. She isn't "my" friend. LOL.

Polyester exotherms *worse* and will probably catch fire. Been there,
done that, kicked the burning pot out of the workshop.

Also the shrinkage will *kill* you as without reinforcement it will
crack round any object you include.

If you *want* a nasty yellow lump, go for it ;-)

If I *had* to do this, I'd use slow cure epoxy at a carefully controlled
low temperature in a PVA mold release treated polished round flat
bottomed metal mold or a PVA treated polyproplyne mold and pour not more
than 1 cm deep at a time. The objective is a flat, puck shaped
paperweight with a relatively THIN object inside. Its probably best to
work upside-down for simple stuff. Pour 1/2 cm top, cure slightly past
gel. Position epoxy dipped object, with something holing it down. Pour
another 1/2 cm and cure again. Pour enough more to cover and this
time cure to a firm green cure. Remove from mold, clean up the
meniscus, sand the back smooth, rough it up a touch and build up tape
dams round the edge. then cast on a layer of opaque black epoxy
(graphite or carbon black in large quantities - its black for the rest
of the process) then what ever weight you want like lead shot, or iron
filings in epoxy. Finish with a thin layer to smooth the base. Post
cure for about a week as near to 100 deg C as you can comveniently
manage, chill , and sand and polish out any defects and glue black felt
on the base.

You may need a bell jar and vacuum pump to get the bubbles out of each
layer before letting it cure. As has been said, best done in Acrylic
casting resin, but if you choose an object that would benefit from a
honey coloured resin, it could look good.

--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk
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