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Observation on hard panning ingredients

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I’ve been dealing with getting glazes with Gerstley Borate, Custer Feldspar, etcetera converted to more available ingredients.  I’ve run into hard panning on a number of the conversions and have had to add Bentonite.  I’m also going to try reformulating to reduce reliance on Bentonite (only because it’s a little inconvenient to dry mix recipes that include Bentonite).

I couldn’t find a whole lot of information on which ingredients cause hard panning.  A low amount of clay is reportedly a significant contributor. Nepheline Syenite is a reportedly a significant contributor to hard panning.  But, what else?  So, while mixing some glazes, I took the opportunity to do a test.  I set aside 50 grams each of individual ingredients in individual jars and added 80 grams of water and let them set. I monitored them over time to see which ones hard pan on their own.  Here are my results:

  • Nepheline Syenite hard panned within an hour.  The rest of the ingredients listed below took a couple of weeks to be able to judge how they hard panned, if at all.

  • All of the following feldspars hard panned within 1 week: Mahavar, Custer, G-200 EU, Minspar 200.

  • Silica 325 hard panned within 1 week

  • The following Ferro frits were semi-hard panned. They were quite stiff but I could stir them up with a little effort.  They were about “half as hard panned” as Nepheline Syenite.  Ferro Frits 3124, 3134, 3195, and 3249

  • Ferro Frit 3110 had some minimal stiffness at 2 weeks and was easily stirred.

  • OM-4 Ball Clay and EPK were happily and fully suspended at 2 weeks.

Whether this is beneficial or helpful, I don’t know! Photo of the lab included.  😊


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Nepheline Syenite is used in cone 6 glazes and is a known hard panner as well as any frit as it's ground glass and is basically small rocks.

The cure for all settling glazes is Magma. It a game changer for any glaze that settles hard

Yes you will need to learn how it thickens the glaze and slows the drying a bit but its just a learning curve

Edited by Mark C.
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A little more detail and a tiny cautionary note.

MAGMA will dramatically thicken any glaze it is added to. Thinning the glaze to a “normal” consistency will cause very thin coats. MAGMA containing glazes must have more viscosity than typical glazes. MAGMA glazes also take more time to “dry” (the water moves into the bisque slower) after dipping or spraying. If high viscosity glazes will not work for you, and/or slow setting or drying glazes will not work for you, you should not use MAGMA.

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14 hours ago, davidh4976 said:

A low amount of clay is reportedly a significant contributor

Yep, clay is the suspender so usually at least 10% or more clay to reasonably suspend in a recipe. Neph Sy has minimal silica and alumina comparatively so what better way to lower melting requirements before boron was a thing. Many always try and have 10-20% clay in their designs to suspend everything else. Glaze Calc helps make this a bit easier these days. Boron, a game changer to use other materials.

Edited by Bill Kielb
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I’ve reformulated a few gerstley borate glazes successfully at this point, and some general things I’ve found:

-if a GB glaze has little or no clay in it, using  frit 3134 for boron and calcium, neph sye for some alumina and the sodium, and epk or other clay for the additional alumina needed will give you a glaze that settles less. Frit 3134 has a lot less alumina for the specific purpose of being able to up the clay content in a glaze to help keep it suspended.

-you may still need to use a little supersaturated epsom salt solution to keep the glaze suspended, but that does work a treat. Some gerstley borate glazes can be prone to slow drying anyways, so you may not notice a big difference in that area.

-you may find some crawling or spitting issues with layered glazes resolve, especially if the glaze had more than 20% GB. 

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try making the glaze in distilled water.   i have such hard water that if i leave any in a container long enough for it to dry out, i can easily pick up some that resembles a potato chip,   

we measure all the ingredients carefully but hard water has calcium (and lord knows what else) that changes the balance.      results?

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  • 3 weeks later...

I let the materials set for about one more month.  Observations FYI:

  • Nepheline Syenite, Mahavar, Custer, G-200 EU, Minspar 200, and Silica 325 hard panned so much that I gave up on trying to cut up the hard pan to get it out of the containers so I could reuse the containers. They all went in the trash.
  • The following Ferro frits were hard panned, but could be remixed with a little difficulty: Ferro Frits 3110, 3124, 3134, 3195, and 3249

  • OM-4 Ball Clay and EPK were easily remixed by shaking the container.

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1 hour ago, davidh4976 said:

OM-4 Ball Clay and EPK were easily remixed by shaking the container.

You might want to repeat in combination(s) with 10 and 15% clay for each. Traditionally potters like to have let’s say from 10-20% clay in their glazes to help keep things suspended.

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