Deflocculate Or Add Water?

[Callie Beller Diesel]

Adding bentonite is only effective in glazes that are very low in clay.

In order to stay suspended in the bucket, glazes need the variable particle sizes that are found in less processed materials, like clays.  If, for instance, you have a glaze that is particularly high in frit (a dense, more processed material with pretty uniform particle size) and doesn't have a lot of clay, because hey, you got all your alumina from your frit, the glaze will fire up pretty uniformly but settle out hard at the bottom of the bucket.  Adding bentonite, which swells considerably when it's wet, allows you to introduce some different sized particles that will help keep your glaze suspended without altering the chemistry of your glaze noticeably.  In practice, this works a lot better if you also use your flocculants (epsom salts, vinegar) along with adding bentonite.

If your glaze already has more than 10-15% clay, adding bentonite is unnecessary for flocculation purposes because the variably sized particles are already present, and just adding epsom salt soloution or vinegar should suspend things nicely. 

[Rick Wise]

22 hours ago, C.Banks said:

Bentonite will work in amounts up to 2%. It is a colloidal clay iirc.

Unfired glazes lacking clay will also powder and rub off pots more easily.

Best solution is to adjust the kaolin(clay) if possible.

Adjust the clay? Do you mean add kaolin?

[C.Banks]

48 minutes ago, Rick Wise said:

Adjust the clay? Do you mean add kaolin?

you betcha'

EPK is a common choice.

[Rick Wise]

What a wonderful resource this is!  Thanks to you both.