Porous casts with Form2 + Castable Wax V1

[jonathanhouse]

Hello all,

I’ve had my Form2 for a little over a hear now and have been working almost exclusively with the Castable Resin and Castable Wax resins. I am teaching myself jewelry casting as I go, so please keep that in mind as you look at my issue.

I’ve been getting pretty consistent porosity on my sterling silver casts lately using Castable Wax. I’ve included links to a couple of pictures showing my most recent casts. After reading through a lot of similar posts here and elsewhere I’ve come to the conclusion that the results I’m seeing are due to an incomplete burnout.

Cast 1: https://drive.google.com/file/d/12jE3iN6HVZJ7sCjDcOGPx77vdD-JnKq2/view?usp=sharing
Cast 2: https://drive.google.com/file/d/12jwhas80yHE8_YZ44mP7nPNInwKXhSD4/view?usp=sharing

For the record, I’m using R&R Plasticast as the investment, and following the FormLabs recommended burnout schedule. Two modifications I made for this burnout was to extend the peak hold to 4 hours and raised the peak temperature to 1380 F. Final flask temperature was at 954 F.

The kiln I use for the burnout is a Paragon SC2, with a single vent hole at the top. Before this run I created three vent air channels at the bottom of the kiln door to improve air circulation.

Casting was via a home-made vacuum table, using an acetylene torch for heating the silver. Silver was a 50/50 ratio of new casting grain and previously cast silver. Any feedback would be greatly appreciated.

[Gcorner]

I’ve had great luck with a
5 hr hold at 1450 F and casting at 925 F

[jonathanhouse]

Thanks for the response, that is on my list to try. Related to that, does the kiln you are using have any sort of active circulation? Trying to decide if I can fix it with the burnout schedule or if I have to modify my kiln

[Gcorner]

Mine just has a hole on the top.

[jonathanhouse]

Thanks for the reply, GCorner - I will be trying that burnout schedule next.

For those of you interested in progress on this topic, last night I tried a new step of vacuuming out the investment at the beginning of the casting temp hold. Using a small rig I whipped up I pulled the flasks out of the oven, and vacuumed them out sprue-down for 10 seconds, then returned them to the oven for an hour before casting. The castable wax pieces came out MUCH cleaner - almost no sign of the porosity pictured in my initial post.

At some point I’ll pull together proper documentation on the steps and results to share with others that are experiencing similar issues. I purchased my Form2 specifically so I could go from print to cast in a single step, and am pleased that it seems to be a reality now!