Casting Bubbles-schmubbles! How to keep them out of your castings

nice thread--wish I had some input--I will just read

 

I've never had any luck with talc, so I use EaseRelease 200 in the molds. This I wash off after with dawn dish soap, and get back the matte finish of the original. (note-the scented talc made the parts smell good, though!)

Also, if the vents are located inside a joint, then a couple of those pinhole sized bubbles will never be seen until re-stringing time and they don't affect the function.

But even being in Florida where the resin is always warm, I do get these bubbles from time to time. I think rotating the mold and gentle tapping it helps a ton. I'm beginning to think these are things we have to live with, unless we want to make piles of each part?

 

I use sandalwood scented talc but I didn't know it was to prevent bubbles. Pat, I get my syringes at the chemist/pharmacy, where I also get tiny shot-glass mixing cups that I can use to accurately mix up to 30ml of resin by volume. I also got some larger (i think 50ml) syringes that I use for silicone primarily ~ those I got from one of the places I buy my resin from.

Catrina, you forgot to mention vacuuming part A and B separately, and also after mixing if the potlife is decent.

 

for measuring I have found that a postal scale that also has grams works really well. Scales at Staples or Office Max are about $100.

 

Yup, I bought a good quality set of gram scales for mixing things by weight. I got it off eBay. I bought a few that died on me, maybe they were cheaper, or couldn't handle the chemicals.. The ones I got now are meant for kitchens and laboratories and are supposed to be sealed to protect from splashes.. it also came with some nifty covers for the screen and buttons.

For mixing by volume I use measuring cups with millilitre lines on them (50 ml increments). I don't mind mixing resin by volume, but I prefer to mix silicone by weight, because it's so hard to clean the part A and B out of the separate containers. Mixing by weight I can put everything in the same bowl and it's super easy to peel out the cured silicone

 

Bottoms up!! Well actually it's probably a medicine cup, but it's the size and shape of a shotglass dammit

 

Oh Gods ~ imagine the internal damage if you drank a mixed cup, and it cured in the digestive system!! I don't want to find out what any of it tastes like, but the tinted part B can look quite juicy.

Honestly you should make a rule right now about no drinking from plastic mixing cups.. get a hold of a bunch of old coffee mugs or something that people can drink from.

 

As long as he knows what he's doing and doesn't actually drink it.. but having drinks in the same type of cups as resin is mixed in sounds about as stupid to me as keeping cleaning agents in old soft-drink bottles and storing them on the bottom shelf where little kids can see and access them...

 

Yesterday at the smooth on seminar..the instructor told us about the quick heat method, but since she didn't have a heat gun she just did a quick dusting of mold release over the bubbles. Worked great!

 

I concur about the wooden stirring sticks - they're moisture magnets, and WILL introduce water vapor into your resin, which will cause foaming/bubbles.
Alumilite sells plastic measuring/mixing cups, but they're ridged on the inside, and make it impossible to stir your resin properly. Stick to disposable drinking cups, either plastic or waxed paper - it's also less traumatic to have to throw away after using them.
DO invest in a pressure pot and air compressor. A vacuum chamber is a convenience and nice to have for degassing, but a pressure pot is an absolute NECESSITY. And did I mention that it's much cheaper than finding a vacuum pump that will pull 29" of Hg?
Denser (or harder) silicon for molds will produce better results, and will be far less likely to distort, or create messy part-lines when casting.

..I guess these aren't so much bubble-removers as just suggestions in general I had to learn the hard way..

 

Hi Pat,

She used smooth on ease release which is a spray. As for other tips......I was kinda disappointed with the seminar. There were alot of people and she was trying to show us so many products that I didn't learn very much that pertains to what we are doing. I've learned much more from this forum and DOA.

 

I do use wooden stirring sticks and I've never had a problem afaik with moisture. I am very careful when I buy plastic drinking/mixing cups that they are smooth in the bottom and around the edges.

 

Yeah it's not very humid here, that might be it.

 

I work in a lab setting and they use shakers to get the air bubbles out of the mixes. I've also heard of touching the cup with something that vibrates like an electric toothbrush (or whatever other type you might have ,

 

:kissy A vibrating tabletop or platform could be all sorts of fun! ....for bubble-removal, of course!

 

You can also warm your molds in the microwave

 

Hehehe .. that reminds me of when I first started learning to cast resin ... I was told the put the resin filled mold on the top of the wasing machine on the spin cycle (to get the bubbles out) ... but silly me .. I put it IN the washing machine on the spin cycle .. needless to say I had to buy a new washing machine!!!

 

:dead
What an expensive mistake! Ouch! Then again, if you've been hankering for a new washing machine... what a wonderful excuse! :confused:

 

I think that if you used an empty foot spa that it would make a good vibrating platform for when you cast i've thought about it many times but i have yet to try it and my foot spa died so i can't try it now

 

dollist: I have a question about weather for you since im in florida too. They mentioned the rain being a problem. Do you need to wait for a day were the humidity is very low? I know we have very few of those especialy this time of year...

 

This is a great thread.

One comment about talc: we noticed tiny black specks showing up occasionally. It may have been from the generic-brand talc. Not sure, but we went with a higher-quality name brand talc, and the problem recurred less frequently.

 

reading all of these posts, i feel blessed that Colorado is almost never humid. I'm going to have enough trouble learning to cast as it is >_<

 

squish'em!!! post-pouring the resin into a warmed mold (i use hair dryer) pop the mold into a pressure pot and increase pressure to between 40 and 70 psi depending on resin viscosity I usually err on the side of caution and use 70 PSI..... works just as well at 40 PSI though

 

I have a few old air pumps for aquariums that vibrate perfectly to remove bubbles. I have a friend who insists he can use a hand held sander (and he's trying it today so that should be a fun story) but I fear that that will actually vibrate SO much that it will splash the resin up and work in a bad way (though he is using Hydrocal which is gypsum based). I used to work in a dental lab and found that we had to use a more gentle setting to avoid this with some of the runnier materials. I think that would also be the case with resin until it has set up a bit, and by then it would be too late.