A boon to casters

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Russianwolf

Russianwolf

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I mentioned wanting a Silicon mixing cup a couple months back and someone pointed out that they are made commercially. So I did some looking and finally pulled the trigger on this set.

Amazon.com: Chef'n SleekStor Pinch with Pour Measuring Beakers, 3-Piece: Kitchen & Dining

Now, admittedly it would be great if they were water clear and all that jazz, but so far I haven't seen that as a problem.

The cups are flexible enough that you can easily control the pour and once the left over resin cures (gentle squeeze) it pops right out. They are also sturdy enough that you can mix aggressively in them without them folding up. I tried mixing Alumilite, PR (castin Craft) and West Systems Epoxy all with similar results.

I'm never going back to plastic cups.
 
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Ed McDonnell

Ed McDonnell

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WARNING WARNING WARNING

I had bought silicone mixing cups off ebay. I found thick resin remants easily popped out of the cup when cured. The thin film that gets left on the sides from mixing / pouring would never fully cure hard in the cups I had and was really hard to get out.

I needed to make a large cast for a non pen related project (about a quart of resin). I've done this before with no problems using various molds (pvc pipe, MDF lined with foil). I figured, why not let the resin cure in the in the silicone cup.

I poured / mixed the resin and left it in the cup in the shop while I went outside to do some work in the yard. A half hour later I came back to find smoke pouring out of the garage. The resin AND the cup were both smoking heavily. A really toxic smoke that choked you and burned your eyes at the first whiff. Like breathing chlorine or ammonia.

I've never had anything like that happen before. I managed to get the stuff outside without killing myself. The next day the silicone cup was all gummy. The resin was all cratered and distored. I ended up throwing everything away.

Silicone cups may not be all created equally and I don't know what role mine may have played in this disaster, but I'm done with silicone mixing cups.

Ed
 
jbswearingen

jbswearingen

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I can't speak to the nearly disastrous event (glad it wasn't worse!), but for the resin not curing along the sides of the cup, simply toss it into a toaster oven at 150*F for 20 minutes and the resin will cure hard.
 
Ed McDonnell

Ed McDonnell

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I had tried the toaster oven to harden the thin layer of remants. It didn't work. It stayed flexible and stuck to the cup. I think there was something about the silicone cups from ebay that reacted with the resin in a not so good way. The cups were probably from china and made with some cheap horribly toxic substitute for the actual ingredients that were supposed to be used.

Ed
 
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Russianwolf

Russianwolf

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This set has three cups and

I have a few runs on the sides of the cups, they don't detach as easily as the disc in the bottom, but are cured to the point that they are not sticky any longer.

The plastic measuring cup I was using prior, once cured, the resin would pop off the bottom after some wiggling and the sides would peel off like a sheet of plastic wrap.

With the silicone, granted I've only done 3 pours so far, I haven't seen the sheets on the sides. I think it is better at flowing it back down to the bottom. If not, it should build up over the next couple pours and come out at some point.

I would think that the amount of resin you were working with may have contributed to the disaster. That much resin in a cup is going to produce a lot of heat (I've melted plastic cups with just an inch or so of resin left in the bottom). And heat changes things chemically. Probably went above the safe temp for the silicone cup. They say these are safe to 650, but I wouldn't try it.

I used West systems Epoxy resin more than PR or Alumilite as it is less likely to cause problems (more chemically inert). One example is casting with West I am getting very good results, maybe a little crazing on the surface of the resin when I peel the plastic tube off. I tried it with PR last week and the results were quite different. The material I was casting was distorted (as I had feared) and it had semi-melted the plastic tube mold (turned it a milky white). When I peeled the tube off, the surface of the PR was still tacky. West Systems is way more expensive, but the results are way better for me. Less heat is produced while curing being one of the benefits.

I'll keep you guys posted on how they work. So far, so good. I'm about to do a bunch more pours starting this weekend.
 
Ed McDonnell

Ed McDonnell

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I think my mistake was buying no name cheap silicone cups off ebay. Who knows, they may have been factory rejects someone salvaged from a dumpster. You never really know on ebay.

When I heated it in the toaster oven the outside of the cup got oily feeling like something was coming out of the silicone. My wife uses silicone muffin cups and they don't do the same thing. That should have set off warning bells for me.

I've done similar size casts before without the drama. I think the heat from the resin curing caused something to come out of the cups I was using and it somehow turbocharged the reaction. The resin wasn't on fire, so the overall temp had to be below 300 degrees, but even the silicone cup was smoking. My wife cooks her muffin cups at 400 with no problems.

The good news is that your cups look totally different than the ones I had, so maybe you'll get much better results. You may not want to use them as molds though....

Ed
 
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ericofpendom

ericofpendom

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I just searched on Amazon UK for these and they only stock the lids:confused: found the cups elsewhere but really expensive, around $15 for the 2-cup size. Probably stick to plastic throw-away.:)

Eric...
 
Russianwolf

Russianwolf

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okay folks an update.

I've been using my cups for afew months now. probably cast about 150 blanks with them mainly using the larger cup in the set (can likely count the number of times I've used the smaller cups on my hand).

What I've learned.

1)None of the resins, if left in the cups have a problem curing. If you leave a small amount in the cup, you will get a nice hockey puck out once it cures.

2)You can peal the sides of the cup if you want to, but it can be a pain.

3)They don't crack or melt as far as I can tell. granted I'm not leaving large amounts of resin in them.

I would say after using them for a while that they work well and I won't be switching back to disposable.

The way I've come to do it is after I've used as much resin as I'm going to use, I pour any excess into a disposable container that gets thrown away when full (you could also have a spare mold around to do a layered cast as you go). I then pour some Acetone in my cup and swirl around. Pour the acetone out (back into a mason jar for me to reuse later) and then wipe out with a rag. It takes less than a minute to clean out the uncured resin, but several minutes to peel out cured resin.
 
J

Justturnin

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Thanks for the follow up. I have been hesitant because I use Alumilite and use Silicone cups to pour my sample color pucks in and after only a few pours they are starting to stick heavily. I think you hit the ticket on swishing the acetone around. I may have to pull the trigger on these.
 
Russianwolf

Russianwolf

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Another follow up

I had gunked up one of my cups with dried resin. Forgot to clean it after use, so it had a thin to medium layer of resin all over the inside. thin enough to be flexible on the sides and thick enough to throw off the measurements. I thought it was a total loss.

Decided to try one trick.

Bought a gallon can of acetone because I needed to replenish. Bought an empty gallon paint can. put the cup in the can and filled it with acetone. sealed the lid and let it sit for better than a day.

Took the top off tonight expecting to find a glob.

nope.

I pulled the cup out and used a paper towel to wipe what was left of the resin layers out. The cup is intact and ready for its next batch of resin.

These cups are sturdy critters.
 
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