Casting and voids

[DB in VT]

Good afternoon,
I've been casting and stabilizing for a couple of years now. My biggest problem, when it occurs, is that I tend to get voids next to the wood when pouring resin in a mold with stabilized wood. I use Alumilite fast. It's as if the resin just doesn't flow into all the areas.
I do most of my work when the outside temperature is not conducive to yard work. I do heat up the "B" part of the Alumilite in a warm water bath because it gets a little thick. My shop is probably close to 60 degrees most of the winter.
Does anyone have any suggestions?

 

[eharri446]

Are you using a pressure pot. I read that when casting wood with Alumilite you need to use a pressure pot.

 

[JohnU]

Here's my suggestions... pressure tank is a must, electric drill for mixing to take advantage of the resins working time, warm the mold and wood pieces as well as part B resin. I use a light bulb in a clamp light over the pressure tank. If you have a toaster oven you can put the wood in it on a low warm setting. Get your resin part B to around 80 something degrees. Part A will be colder so it shouldn't speed up the curing time but It will mix quicker so you can pour sooner. Good luck!

 

[Kenny Durrant]

Just thought I'd add a little to the group. I don't cast much at a time so I use a stirring stick instead of a drill. Any thing I'm going to cast goes in the mold and then the whole thing goes into an oven for 45 minutes. That way I know it's dry and everything is warm. As mentioned above I warm my part B before mixing to thin it down or just because it works for me. I use a candle warmer to heat the resin, since I use small batches. When the time comes I add part A, mix and pour and put straight in the pot. No playing chasing bubbles that's what the pressures for. I found it's better to get it in the pot ASAP rather than poking at the bubbles. I also used to use the Alumilie Fast but when I switched to the slow I saw no bad effects just more time to mix colors and resin. Back to your original problem when I found the voids on the side I thought the resin might have been setting faster than the bubbles could surface.

 

[RobS]

Using Alumilite Clear

1) I pour a little resin in the mold so when i push the wood in it has resin present to start pushing out the air bubbles

2) I have cast a bit with wood burls with a lot of cavities. In this case I pour some resin directly on the burl (wearing glove) and roll the burl piece around to get it coated, then I drop it back into the mold and pour the rest of the resin in.

Also make sure a rubber band or something is holding the wood in place.

***Also, I have been known to take a ball burr on the dremel and open up cracks and create baths for air to flow out and resin to flow in.

Then, I pressurize it (my pot will take 75psi).

 

[RobS]

Example of a casting where the dremel was used to provide flow paths. The tail end was 100% dremeled out

 

[DB in VT]

I do use a pressure pot. Minimum 2 hours at 55 psi. I generally warm the "B" part but I can't tell you what temperature; it sits in a warm water bath for ~30 minutes prior to mixing. The mold generally goes into the pot within a minute of the pour; often less.
I usually mix with a stick because I'm mixing just a very ounces at a time; usually in a 8 oz plastic cup.

 

[JohnU]

I'm guessing the part B resin is still a little too cold and your spending too much time mixing with the stick because of that. I would suggest changing to Alumilite Slow. It will give you a few more minutes of working time and should fix the problem.