Air in Ceramic Slurry

[celticmad]

Can anyone tell me if there is a method for removing air from ceramic slurries ?.
We are dipping plastic patterns in the slurry but bubbles are causing scrap on the finished castings.
Anti - Foams are not very effective.Dipping at an angle is better but again not totally effective.
Speed is an important factor.

 

[Ceramicguy]

Put the slurry in a chamber and draw a vacuum ~29". When it stops bubbling it should be deaired. As long as the surface isn't radically disturbed (reentrained air) it should stay reasonably bubble free.

 

[celticmad]

Thanks
Ceramicguy but unfortunately not an option....a full scale production process whereby a board containing the moulds is dipped into the pot and rotated every two minutes.Vacuuming would be too expensive and take too long.
Thanks anyway mate

 

[Henshall]

The reply from ceramicguy was correct. I suspect you are producing your slurry with a relatively high speed impellar and you are introducing air in the batch that way. It is relatively easy to de-air tha slurry in a vacuum vessel prior to pumping to your dipping tank. Ensure you are not introdcing air into the slurry during the pumping operation by always having a slight rise on all the delivery pipes.
Frank Henshall