Well, Lee, let me give you a couple of tips. First, Don Ward (It's Virgil) and I have been friends for a number of years - and have spent a number of hours together experimenting and certainly talking and sharing our experiences and our experiments with casting, face-to-face and on e-mail.
When Don put together a very detailed "paper" on casting Polyester Resin, he wrote it as a final solution process to eliminate several problems he was getting.
The point to remember was that Don's casting WAS NOT the normal need that most of us encounter. That is, putting a couple of molds in a Pressure Pot and making enough parts for generally 2 pens at a time. Don's problems (and solutions) came about because he was casting 6, 8, 10 or more pieces at a time. Also, not just 7mm tubes (and skins) at a time, but rather tubes for other larger sized pens. He was having a terrible time - and wasting a lot of skins in the process. Through his continued experimentation (AND a lot more patience than I would have had), he discovered the addition of his vacuuming procedure finally eliminated the problem - and since then has produced nothing more than perfect, clean, bubbless castings.
SO! Unless you plan to do multiple parts casting, FORGET THE VACUUMING! It's a waste of time and money. And I challenge anyone to prove me wrong about this.
Two molds - 4 pen parts (two complete pens) - 30-40 minutes under a PRESSURE of 30-40 psi, 4 drops of catalist per ounce and you can go out and exhaust your pressure pot, take out the molds, take them inside and in an hour or so, turn them over and slam them down on your kitchen countertop a couple of times, removing them from the mold (they'll still feel a bit stickey on the surface) and just set them aside and let them "air" overnight. The next day they can be turned.
This is a very SIMPLE process and doesn't need to be made more complicated for the average PR caster. Every 40 minutes you can re-mix some PR and head for the pressure pot. By the end of an evening, you can have a pile of new blanks - AND NOT ONE BUBBLE - EVER!!
Get your pressure pot Lee - and get to work. Soon, BUBBLES will be something you'll never think about!
Regards,
Jay
quote]Originally posted by leevis
<br />I've just started casting my own blanks with PR. I'm just mixing colors; no embedded items. So far, I've been very pleased with the results. Occasionally, however, I get very tiny bubbles in the finished casting. I'm very careful when mixing and pouring, but I guess sometimes the bubbles just can't be avoided.
My question, would it be better to put the resin under a vacuum, or cure it under pressure? I'm going to get the pressure pot from HF and will also pick-up the vacuum pump if that's the way to go.
[/quote]
]) and a hand-operated brake bleeder (like from Harbour Freight) ... maybe eight to twelve 'pumps' with the output of the brake bleeder on "exhaust" instead of "vacuum".
