Moisture (?) in resin

[Lawton Maner]

I tried to use some Smooth On casting resin which I hadn't opened in several months last night and the finished product looked like a piece of Swiss Cheese.  Is that moisture trapped in the resin, and what can I do to fix it?

[finescalerr]

The guys most successful at casting resin use a compressor to force the air from resin in the mold. I don't have detailed instructions but one of my Modelers' Annuals has an article by Bob Uniack describing his general process. -- Russ

[Lawton Maner]

I'm familiar with the technique.  The easiest method requires a spray painter's pot and lots of air pressure (usually more then 95 psi.) which can become a bomb if the pot isn't a good one because most of them are rated at about 50psi.

[lab-dad]

I used my a/c vacuum when I did the silicone molds.
It sucked all the air out and is not dangerous.
May be you can find an inexpensive one?

-Marty

[Ray Dunakin]

Moisture will definitely do that.

[Lawton Maner]

Marty:

I've used my Shop Vac to de-air rubber when moulding and plaster when casting in the past, but never the resins.  Maybe it's time to step up to the bir times.

At a convention a couple of years ago there was a presenter who was making 1:87 scale windows using a vacuum system which produced scale mullions. Maybe its time to see my Snap-On dealer and get something capable of "sucking the chrome off.

[lab-dad]

dont bother with snap on - you will overpay.
find a robinair dealer and see if he has a pre-owned unit.

[Ray Dunakin]

BTW, you can greatly extend the shelf life of the resin by spraying a shot of "canned air" into the containers before reclosing them after each use. By canned air, I mean the stuff used to clean dust out of electronics and cameras.

[Bexley]

Huh, never thought of that. I suppose it probably isn't oxygen in those, is it. That'd be kinda dangerous for an office product.

[lab-dad]

FWIW I recently saw fairly decent vacuum pumps on ebay for a good price.
-Mj

[Stoker]

I concur with the vacuum box suggestions. It has been a long time, but I did a lot of plaster and resin (mostly Pecan dust filler type) casting when I was growing up. My mother ran an art/craft/hobby store, and classes teaching painting of figures (think Geese and Amish figures) was a mainstay and these required dozens of castings for each class so we always had a table full of castings going. Initially we just poured them and there were a lot of bubble issues. The first thing I tried to help this was taking an orbital sander and buzzing the table, which shook most of them loose, and then my dad made a little vacuum box hooked to a shop vac and that was a game changer. It was just a simple box about 2'x2' and maybe 6" deep with weatherstrip around the base, with the obligatory plexiglass window so you can see the bubbles boiling off. This could be used to cover several little molds at once, and then moved to the next batch. It is impressive just how fast the bubbles will boil off with only the moderate vacuum from a shop vac. 90% seem to come out in the first couple seconds, and then a few stragglers come out during the next 20 seconds or so. Even so, there were some bubbles that would adhere to some molds, so the routine became to put the vacuum box on and then also vibrate the table for a few seconds with a sander. Presto! No bubbles.