I tend you use ceramic grade rutile which is darker than light rutile and use that unless light is specified. As far as the whiting goes, aske your supplier what the difference is. I know with some wollastonites for instance, there is a bit of iron, so you might want to find whichever whiting or wollastonite is purer. Although Custer and G200 can usually be used interchangeable, Custer has a bit more silica which can help prevent crazing if your recipe is on the border as far of expansion is concerned. If you know how to reformulate a recipe, with or without software, it's easy enough to reformulate it for a different spar; but in most cases, either one would have a good chance of working. The frits aren't interchangeable really, because although thy all have boron, the other ingredients vary. 3195 has more alumina in it for instance and I use that if I want a high alumina recipe and don't want too much clay in the recipe. You get a bit more boron for the money in 3195 which is why I often use it, but I make sure it fits in on a molecular level with my recipe.
If you're working at cone 6 I would not advise getting your list of materials too small.
You can do without wollastonite and reformulate the recipe for silica and whiting which is what wollastonite is composed of; but you'll have to back engineer the recipe.
For cone 6, minimum materials list, I would advise
Frit 3134 Neph sy F4 soda spar Custer epk OM4 ball clay whiting talc dolomite silica - 200 mesh spodumene zinc oxide bentonite Zircopax or Superpax Tin Oxide and your basic coloring oxides
With these ingredients you can formulate alkaline glazes, calcium or alumina matts, etc. These are also the ingredients you would most commonly find in cone
6 recipes.
If you want to extend the list, you can also get some of these to play around with: wollastnite
barium carbonate strontium carbonate Lithium carbonate Gillespie Borate or Boraq (Gerstley substitutes) Volcanic ash Frit 3124 Frit 3195
Regards, June
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