Kona F-4 to minspar 200 feldspar substitution

[GlazeGus]

I have read on this forum that Kona F-4 and minspar 200 have very similar composition, with many reporting that a 1:1 substitution has served them well. When I used Glazy to balance the UMF and perform the sub I was surprised by how different the recipes came out (see photo) I am wondering if I should trust the Glazy adjustments or just proceed with a 1:1 substitution.

 

BTW, I am trying to reformulate Malcom's shino (no Redart) as reported in John Britt's High Fire book

[Min]

Hi and welcome to the forum.

What do you show just doing a one for one swap? This is what I get using Insight with their materials database.

[GlazeGus]

Hi Madeleine,

Thanks for sharing your Insight analysis and for suggesting that I simply look at the 1:1 UMF. When I do the 1:1 in Glazy the two UMFs are really quiet close to each other and to those you obtained on Insight. So I guess my problem was the 'Target' and 'Solve' function on Glazy - I'm new to this and still have a lot to learn.

Though the substitute recipes are close they are not identical. So I guess I have two follow up questions. 1) are these essentially close enough that the slight differences in the Si02:Al2O3 rations and calculated expansions are negligible and 2) how would I adjust the relative amounts of Kaolin, Ball clay and Neph Sye to get these closer to 100% identical. 

[Callie Beller Diesel]

The target and solve function is supposed to get you a chemically identical recipe, one that will *theoretically* look the same. And that’s what’s happened here: all the ratios except for the calculated expansion in the first example are identical, and even those are only off by the faintest amount. 

However, target and solve doesn’t address bucket behaviour, which affects how a glaze applies to the pot, which in turn can affect the final look. Bucket behaviour is affected by things like changes in the total amount of clay, or in the amount of soluble materials. The total amount of clay in the target and solve recipe is a few percent higher than the original, and there’s a bit more soda ash. Not a lot in either case, but it could make this version a bit more prone to crawling than it already is, if applied thickly. 

The straight substitution recipe only has marginally more silica, and a slightly different expansion rate. But again, those changes are small, and any differences in the look of the glaze might depend on the clay body (crazing from expansion rate) and the firing cycle (gloss level from additional silica).

 

Best advice from here is to try them both and see which one you like better. Glaze software eliminates some physical testing, but  not all. 

 

[Min]

The only thing that might make a difference is the slight increase in silica but my hunch is it won't be significant enough to make a difference, testing will tell.

Given there is no added standalone silica in the recipe to reduce it and get closer to an identical UMF you would need to reduce some of the silica while keeping the other oxides balanced. This is what the Target and Solve function did with it, reduced the silica by reducing the Nepheline Syenite then increased the Minspar (it has less silica than Nepheline Syenite) to rebalance the Sodium and Potassium then adjusted the Ball Clay to adjust the alumina and rebalance the silica. 

As well as how the glaze behaves in the bucket particle size and how well they melt comes into play also. 

[GlazeGus]

Thank you to Madeleine and Callie Beller Diesal for your thoughtful replies, this is really helping me to understand the limits and benefits of the glaze softwares. I think I will take your advice and test both the direct 1:1 sub and the Glazy target and solve recipe! I'll do my best to report back what I find.