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FFF Feldspar is one of many brands of potash feldspar. Feldspars come in two main categories - potash and soda. The basic mineral contains both sodium and potassium, but in varying proportions depending on the source where it was mined. If there is slightly more potassium than sodium, it is classified as a potash spar; and conversely, if it contains slightly more sodium, it is called a soda spar. The various brands of feldspars often can be substituted with another of the same classification, but crossing the potash and soda spars may not work as well. In some areas of the world, the feldspars don't carry particular brand names but are sold as generic potash spar or soda spar. In all cases of substitution, test a small batch to ensure the chemistry of the new material works properly, and tweak as needed to correct any imbalance.

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Using Minspar in place of the FFF spar and rebalancing to 100 gets me this, it's pretty close chemistry wise. Just needed a little tweaking, as you can see it's basically the same recipe. I left out the colourants and bentonite, just use the same amounts of those. Apart from the bentonite there is zero clay in this recipe, it's likely to sink quickly in the glaze bucket. Alumina is a bit on the low side for a durable glaze. If you try this version please just try a small test batch first as what looks okay on paper doesn't always translate to what works on the pots.

Cone 6 Altered recipe:

M Materials Amt
  minspar 200 34.77
  silica 29.45
  ferro frit 3134 17.38
  whiting 9.20
  dolomite 6.14
  zinc oxide 3.07

edit: I redid it getting the sodium and potassium exactly the same, swapped the minspar for custer plus nepheline syenite. Version below is exactly the same chemistry wise to the original. (Version above has the overall total sodium & potassium totalling the same but there is a slight difference in the quantities of both vs original).  With some colourants, copper for example, the balance of the two fluxes, sodium and potassium, makes a difference with colour response with others not so much.

Code #


M Materials Amt
custer feldspar 15.89 15.89%
silica 32.97 32.97%
ferro frit 3134 16.88 16.88%
whiting 9.93 9.93%
dolomite 5.96 5.96%
zinc oxide 2.98 2.98%
nepheline syenite 13.90 13.90%
epk 1.49 1.49%


Edited by Min
added a better recipe
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