Flocculation Issues (Again!)

[Crooked Lawyer Potter]

Flocculation continues to confuse me.  I have run into 2 problems I need help with:

1. My Fat Cream glaze is "overflocculated" in that it is too thick and the coat is uneven.  How should this be addressed?  Just more water to thin it?

2. My Matte Base glaze has perhaps also been "overflocculated" but in the sense that it remains thin and watery and no longer responds to epson salts and indeed seems to get worse the more I add.  I have added magma to it but this too is unavailing as it continues to be runny and thin coating like a deflocculated glaze.  Is it possible to overshoot with the epson salt?  And if so, how do you reverse?

Fat Cream

Neph sye.  45

Gerstley borate.  25

Silica.  20

OM 4 Ball Clay.   10

Zircopax.  8

Rutile.   1

 

Matte Base

Custer feldspar.  40

Whiting.  16

Silica.  16

EPK.   10

Frit 3124.   9

Talc.    9

[neilestrick]

In either case you can try letting it settle and scooping off a bunch of the water, then replacing with fresh water if needed, or mix with another batch of glaze to dilute the effects.

[Callie Beller Diesel]

With 25% gerstley plus some Neph Sye and ball clay on top of that in your Fat Cream, I think if your specific gravity is correct, it’s one of the few times I’d suggest using a few drops of Darvan to thin rather than water.

For the matte base, I’d go with what Neil said. If you’ve added too much epsom, it’ll make everything flock together...at the bottom of the bucket.

 

[liambesaw]

In small amounts flocculants normally flocculate particles of clay.  But if there is too much flocculant added it only flocculates itself.  It has an affinity for itself, so the only way to really remove it is to add something that makes it insoluble and then filter it out.  You can get it freezing cold and then sieve it, I think this is the best way.

Or you can wait til the summer and remove the water.  With all of those soluble ingredients it will probably alter the glaze chemistry a bit when you remove the water, but it should be OK.

 

If you want to experiment you can take a small quantity of glaze and add soda ash solution, this should cause the epsom salts to precipitate out.

[Min]

While specific gravity (sg) measurements vary according to glaze recipe plus to a lesser extent the bisque and application method we have no clue what the specific gravity of your glazes are. Your first glaze might need more water if the sg is excessively high and the opposite for your second glaze. How much Magma did you add to the second glaze? How did you add it?