Bruce In Bangkok wrote:
On Thu, 3 Dec 2009 12:57:01 -0700, "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.
That's what I was afraid of. One of the reasons I was considering aluminum
as it transfers heat very efficiently, and I have some. I also have epoxy
on hand which is why I was considering it. How about small batches, partial
cure and then next pour?

If you mix epoxy rich enough that it gets really hot the aluminum
molds will probably not absorb heat fast enough. The reason is that
the heat build-up actually causes the mix to react faster so it is
somewhat of a circle. More heat faster reaction causing more heat...

If I may add something here, Bruce?

The heat buildup works from the inside - out.
So absorbing heat at the outside isn't going to stop it from boiling in the middle.