At a flee market I picked up a block of epoxy into which several Morgan dollars had been embedded. So now I have a block (actually the cast of what appears to be an 8 oz cup) that I want to remove/dissolve the epoxy from. Any idea how this can be accomplished?
You’re sure it’s epoxy? This is not commonly used to embed interesting items, as it tends not to be notably transparent. I’m thinking that acrylic plastic is more likely.
Whatever it is, the general answer is likely to be: heat. Almost any plastic-like material will succumb to this long before silver dollars do.
- Go to Home Depot
- Purchase 1 gallon of Acetone
- ???
- Profit!
Acetone is great - until the resin hardens.
It may be a casting resin - those can be transparent (at least close).
Heat will produce some nasty vapors
I’m going to guess that whoever created this think did not think to coat the dollars with anything resembling mold release.
A machine shop ca cut through the block and eventually get to the coins. It will cost much more than the coins are worth.
Take it to a TAP Plastics store - they may be able to tell you what you’re up against.
If you want to try your hand: While you’re at TAP, pick up some resin which is as close to this stuff as you and they can find.
Now, start looking for a cheap band saw.
Use the resin and some quarters to re-create the problem. Now start running the new block 'o stuff through the saw.
If you can end up with a slice of resin just slightly larger than the coin, try tapping on the edge of the block. place it in a vise and see if you can fracture the resin shell.
I am not certain of the melting point of silver vs melting point of a resin. i would look that up REAL carefully before applying heat more then a cheap electric heat gun can produce. Maybe you could luck out and have the metal expand at a different rate than the resin - that would shatter the resin.
Simple, this is NOT going to be
Try MEK?
Hot n-methyl pyrolidone.
Some quick Googling yielded this:
Temperature at which epoxy starts to lose significant strength: 350 F
Melting point of coin silver: 1615 F
If it’s acryllic, a cheap electric heat gun won’t actually be able to melt it, but it will be able to render it soft and rubbery.
Water-clear casting resin is usually polyester, which is a thermosetting plastic - so can’t be melted, but it should break away from the coins once it’s cut down a bit - a hand saw can be used to cut away chunks of the plastic.
Just hit it with a hammer. The plastic doesn’t adhere to the metal. If it’s really soft you may have to use a saw as Mangetout suggests. But a few good whacks should break it. I think for coins it would probably break where the plastic meets the coins and a few more hits and some prying should remove them.
Just boil it in plain water - if you want to make it easier, use a pressure cooker
The differential expansion due to temperature is enough to dislodge the coins from usual plastics
Sometimes I need to take the blades out of shaving razors and this is the method I use.
I think this is the best idea. Try freezing it first.
Im not in any way handy, which is why I’m posing this as a question instead of an answer.
Would you be able to take a power sander/angle grinder to the stuff? Or just power drill a few holes near the coins and pry the thing open with a screwdriver?
Freeze it and whack it with a lump hammer.
I’m prepared to be corrected, but from what I’ve heard, a general rule in grinding is to never grind anything that doesn’t spark. The idea being that material that is too soft to spark can build up in the pores of the grinder and cause it to burst. (Now I’ll go google it to see if I’m crazy)
cast iron and hardened iron sparks easily because it contains austenite.
… lots of very hard stuff won’t spark, and you can use a grinder on soft stuff.
Whats wrong with grinding a bit of chalk ?
resin grinds easily. The grinder is just a very coarse grade of sand paper and the more coarse the better for avoiding it clogging up. Very fine sand paper rapidly filmed up with epoxy resin’s dust.
What you don’t want to do is melt the resin and have the grinder disk sieze in the cut… but the grinder disk is blowing a lot of air with it and the clear resin is very hard and brittle in effect… the grinder easily turns it to dust rather than melting it.
Thanks for all the great advice. I will work on it this weekend and get back to you with my success (or not).
I’d consider keeping the coins in the plastic. Removing them will probably result in damaging the coins.
I cast a few shells for my high school biology project. Teacher ordered it as a kit from a supply catalog. I used one of the labs pyrex beakers. I had to mix the plastic and resin at home because an oven was needed. It was a very low temp. Probably 225 F or 200 F. Then it had to cool overnight.
Next day it wouldn’t come out of the beaker. Teacher had me break it. I got charged a lab breakage fee. Got a B on the project because there was an air bubble under one of the shells.
Here’s a standard casting kit like I used. I’m sure those coins used something similar. It’s a great way to preserve and display small items.