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Low Fire Clay Flux


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Hello and Thanks for your input!


I am trying to formulate a low fire clay body that is close to vitreous and a good glaze fit.

Also I mix up all the clay for my high school classes so a quick easy no weigh recipe is essential.

I use about 3,000# of dry materials a year.


Right now I my recipe is


33-Texas Talc

33- OM4             recipe cost $11.3 per 50#

33- Roseville


Absorption is about 12%- Far to much 


I would like to use gillespie borate in the clay because it is mildly inexpensive compared to frit 3124 $1.9 vs $1.02

I can not find any recipes online that use GB in clay....probably because you shouldn't.


I was thinking something like


25- epk

25- GB        recipe cost $21.3 per 50#

25- om4

25- talc


However I would love to stop using talc- Asbestos fear- so maybe something like


33- epk

33- om4   recipe cost $24 per 50#

33- GB





25-om4  recipe cost $20.9 per 50#





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Absorption is about 12%- Far to much

A sure sign not enough flux is present to achieve vitrification.



I can not find any recipes online that use GB in clay..

Any flux used in a glaze, can be used in a clay body: but that does not mean it is a good choice. Boron is believed to add translucency to porcelain bodies: but it is usually sourced as a boron frit to achieve a complete melt at lower temps. 3124 is a good choice. Nep Sy is also used, often in combination with frits.


Cannot comment on your clay recipes because I am not sure if I am understanding them correctly. A couple are just all clays, no silica or fluxes. Talc has magnesium which is a flux, but not generally used except in kiln shelf recipes. That much talc will kill what plasticity the other clays add.


I do not deal with low fire clays or glazes, so there is not a lot I can add. I do know that as you continue to drop from cone 10, flux increases to compensate for lower peak temps. Cone 10 generally runs 25%, cone 6 around 30%, so I would expect low fire to be 35% or more of flux. Obviously that is generalized, and many issues effect those additions.


Try doing a search of the forum on low fire clay/s.



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you refer to low fire clay but do not give a temp, cone or reason.  if your kiln can handle cone 6, there is a very good, simple recipe for a cone 6 clay that is very inexpensive.  look for an old post  "making clay 101"  from 2013-4.


the recipe is   redart               50%

                      XX saggar clay 50%.


yes, that is all except water.   the color is a warm red and the clay is very strong, i do not know about vitrified, i always apply glaze.

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Recipes for low fire vitrified white bodies can be found on the Google. They all use frits, though, because they work. Generally with those types of bodies they are only suitable for small pieces, and wouldn't be good for the poor construction that kids are known for. It would be far easier to work on bringing down a cone 6 body to cone 2ish. Even 4 cones will have a huge impact on the life of your elements.

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That might be the best route for simplicity and costs. Red Art has enough fluxes in it without requiring any additions. EPK has very little, and OM4 has virtually none. Will not work for cone 05 though: I think Joel's link is the best route in this case: confirmed by Neil.



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