Mosk:
I use Micromark 2 part CR-600 casting resin. I hate it. No matter what I do I can not avoid airbubbles at all. I have a vibrating table, I have tried the pouring in just a little resin then blowing on it with coffee straws, I have changed how I do my sprues everything. I can not avoid the very small airbubbles. It would not be that bad if there were just a few airbubbles but the airbubbles are EVERYWHERE!
So is there a better resin to use?
I have been looking at this:
http://cgi.ebay.com/Polyurethane-Casting-Resin-liquid-plastic-48-oz-kit-/140543066164?pt=LH_DefaultDomain_0&hash=item20b9050034#ht_1121wt_702
what do you guys think. This resin has always done this. I have used other resins before and even metal and not had this problem so I have no clue if I got a bad batch or what but this stuff sucks.
Any advice?
GRNDL:
The stuff in the link appears to be the sort of thing you are looking for: an ultra-low viscosity resin with a relatively long demold time. This means that air bubbles will not be able to remain inside the fluid and it will give you time to poke inside the mold to dislodge air bubbles before the resin starts to bloom.
Some tips:
1. When mixing, try not to “fold” the resin on top of itself, trapping air bubbles while mixing.
2. When done mixing, tap the mixed resin and allow the bubbles to dislodge. You’ll need a long demold time for this, other wise you risk the resin blooming while its still in the mix cup.
3. Don’t pour the resin all over the mold. Pour it in one place and let the resin slowly push its way over the mold. This way, air will be displaced as the resin seeps into areas of the mold, rather than being trapped underneath the layer of resin.
4. When you’ve finished pouring the resin, get a toothpick and poke the corners of the mold and wherever there is a trapped air bubble. Just poke it a bit to push to displace the bubble and it will, hopefully, come to the surface. If you’re using a viscous resin, this probably won’t work, since the bubble will doubtfully not be big enough to overcome the surface tension/viscosity of the resin. That’s why you need ultra-low viscosity resin.
Personally, I use Smoothcast 300 series resins. They mix clear, so you can see through them, but bloom white/off white when you’re done. Smoothcast make a wide variety of resins, with different demold times and viscosity, so you can choose which one you feel will work the best for your casting needs.
This page has a chart comparing all the available SmoothCast resins:
Sculpture Supply Canada - Product Detail
Although its a Canadian site, the info should still be helpful to you in the US. It is available from the US, but I’m not sure from where. You might want to try “The Compleat Sculptor” if you’re interested.
zobo1942:
The stuff in the link appears to be the sort of thing you are looking for: an ultra-low viscosity resin with a relatively long demold time. This means that air bubbles will not be able to remain inside the fluid and it will give you time to poke inside the mold to dislodge air bubbles before the resin starts to bloom.
Some tips:
1. When mixing, try not to "fold" the resin on top of itself, trapping air bubbles while mixing.
2. When done mixing, tap the mixed resin and allow the bubbles to dislodge. You'll need a long demold time for this, other wise you risk the resin blooming while its still in the mix cup.
3. Don't pour the resin all over the mold. Pour it in one place and let the resin slowly push its way over the mold. This way, air will be displaced as the resin seeps into areas of the mold, rather than being trapped underneath the layer of resin.
4. When you've finished pouring the resin, get a toothpick and poke the corners of the mold and wherever there is a trapped air bubble. Just poke it a bit to push to displace the bubble and it will, hopefully, come to the surface. If you're using a viscous resin, this probably won't work, since the bubble will doubtfully not be big enough to overcome the surface tension/viscosity of the resin. That's why you need ultra-low viscosity resin.
Personally, I use Smoothcast 300 series resins. They mix clear, so you can see through them, but bloom white/off white when you're done. Smoothcast make a wide variety of resins, with different demold times and viscosity, so you can choose which one you feel will work the best for your casting needs.
This page has a chart comparing all the available SmoothCast resins:
http://www.sculpturesupply.com/detail.php?id=796550&sf=subcategory&vl=Smooth+Cast+320&cat=Liquid+Plastics
Although its a Canadian site, the info should still be helpful to you in the US. It is available from the US, but I'm not sure from where. You might want to try "The Compleat Sculptor" if you're interested.
GRNDL
Wow! Thanks for sharing all that great information!!
Xander:
I use the same product as GRNDL, and it has always served me well. 
Grimstonefire:
I’m going to get through the Biresin from Tiranti I have before moving over to smooth cast. I need one that has a longer working life before curing.