Ingredients that contribute to fast settling or hard panning

[davidh4976]

We have two glazes that settle very quickly (one recipe below) compared to the rest of our glazes. What ingredients cause a glaze to settle and/or hard pan faster than other ingredients?

From my collection of notes from various sources, I suspect the following, but would appreciate your feedback:

• Dissolved sodium, such as from Nepheline Syenite and some Frits (3110) can cause deflocculation.  Deflocculated glaze will hard-pan.
• Other materials that can encourage hard-panning are: wood ash, soda feldspar, nepheline syenite, lithium carbonate, and many common frits such as 3110 (644?)
• Insufficient clay in a glaze (I add 2% Bentonite to recipes with none or very little clay, and 1% Bentonite for recipes with less than 10% clay. If the recipe has over 10% clay, I do not add Bentonite.)

I have been reformulating our glazes because of the shortage of Custer Feldspar and Gerstley Borate and have avoided the above items with good results on the glaze results and on keeping the glaze in suspension.

This is one of the two recipes that settles quickly compared to our other recipes. (The other glaze that settles has the same base, but slightly different colorants/oxides.)  These two recipes are the only ones that use Frit 3124, so I am considering reformulating without Frit 3124.  Does Frit 3124 contribute to settling/hard-panning?

silica	16.000	15.38%
whiting	16.000	15.38%
epk	10.000	9.62%
ferro frit 3124	9.000	8.65%
talc	9.000	8.65%
G-200 EU Feldspar	40.000	38.46%
red iron oxide	2.000	1.92%
bentonite	2.000	1.92%

[Min]

1 hour ago, davidh4976 said:

Does Frit 3124 contribute to settling/hard-panning?

Yes it can over time. If you have 3134 then you could reformulate the formula with that which would give you room for more epk in the recipe. Or add a small amount of epsom salts solution to help flocculate it. (after measuring specific gravity)

Edited January 31 by Min

[neilestrick]

Most everything but the clay wants to settle out. Some more than others, but having enough clay in the recipe is key. 10% clay is the minimum I shoot for. If it still settles out, use Epsom salts to flocculate it, which gets everything to stick to the clay so it doesn't settle so much.