[Elmoclayman]

Hey all,

I have been making some slip cast mugs and I keep getting bubble that form on the inside of the mugs. After I pour out the slip, when I look on the inside of the mold, I see little voids from what I can assume are bubbles in the slip. They range from about 1/8th inch to 1/4 inch. I can smooth them with a loop tool, but this is pretty time consuming.

I do vibrate the molds with a vibrating sander after the initial pouring for about 30-45 seconds, but after that I just keep the slip topped off until I'm ready to empty the slip out.

Any suggestions on how to get rid of the bubbles?

Thanks,
Brian

[Mark C.]

A few thoughts
Are you introducing bubbles when you mix your slip?The mixer blades should be well below slip top level
Are you bringing in bubbles when you pour your molds?Take a look at how your are pouring them
Are you vibrating enough and long enough for the bubbles to get out?
And last how are you draining the molds as the bubbles are only on the inside wall you said?
Mark

[Lucille Oka]

Try to post some pictures of both the casting and the mold surface if you can.