First cast with pressure. Ugh!

[alankulwicki7]

So I finally got a pressure pot the other day and put it to use last night. I tried to follow the advice from other posts and the library but my castings came up well short of my expectations.
I started out by gluing some fabric to the tubes using CA. Then I put some nails in the tubes for weight, added a little play-doh at each end and then made some blocks out of maple to hold the tubes in the center of the molds. Then I gently filled the molds with some PR and put them in my pressure pot at 45psi.
This morning when I went to check on the castings there were some small bubbles in one area of the fabric. I think this might be because the CA was not thoroughly dry and was still off-gassing.
The other problem I had was that the resin ended up compacting enough so the top of my item was barely under the resin.

When I filled the mold with resin, I made sure that it was full (and almost over flowing. Any advice as to why the resin came up short in the mold?

PS I'm hoping to get this right because I want to enter the casting contest this year!

 

[JohnU]

A couple things.... First, if your using polyresin like from Michaels or Silmar, it will shrink as it cures. I would suggest you cut up the resin that didnt turn out and use it instead of the maple blocks. Wood will soak up resin and possibly add more air to your pour as bubbles work out of the wood. I always let my glue set for at least one day, sometimes more depending on how much was used. Lastly, warm the resin to thin it out before you pour it. Some use warm water in an ultrasonic cleaner tray but for me I just position a clip light, with a bright lightbulb, next to the cup for 15 or so minutes , stirring and rotating the cup three or four times. Keep with it, you'll find what works for you. Good luck!

 

[NewLondon88]

In addition to what John said, you might find some of your missing
resin inside the tubes. That much pressure is likely to blow right past
the clay unless you have something inside holding it from collapsing.

 

[alankulwicki7]

Thanks for the advice. FYI I am using the PR from Micheal's. I'm going to make up a few more of these and try again. I just hope I can get it to work because I have a very limited supply of material....

Also, should I try less pressure?

 

[its_virgil]

Silicone or rubber plugs work best. Real corks and any wood used will (or may) add air to the mixture as John has noted. Also, as the resin heats the air inside the tube will expand and if the seal of the plugs is not really tight you will have lots of bubbles on the ends...so I've been told ;-) . Plug one end, pack play dough inside and then plug the other end and get rid of most of the air. I once did this but no longer do. Silicone plugs seal really well.

Impatience is one of the enemies of new casters. Anything glued on needs to out gas and totally cure for at least a day...I wait two. Good luck and don't get discouraged...
Do a good turn daily!
Don