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Feldspar Substitutions?

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In my recipes that used K4 I am now using Minspar. There is a bit more silica in Minspar, the rest of the chemistry is fairly close. If you don't use a glaze program then myself or someone else here could do the conversion for you if you post your recipe.

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My materials supplier says use minspar 200, that it is the same thing ???


Thanks, guys!   :)



Recipe is as follows.


Sea foam Green  


Soda feldspar    41

EPK                     5

Silica                 27

Whiting              15

Zinc Oxide         12




titanium           5

copper carb     5

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You could probably just sub the minspar 1:1 for the soda spar. Was it F4 you were using before? If so and you want to get picky with a very close match the new recipe would be:


Minspar 200    41.6

Epk                   6.1

Silica                24.9

Whiting            15.2

Zinc                 12.2


total:                100


titanium            5

copper carb     5 


When I just use soda feldspar the rebalanced recipe would be;


Minspar    41.2

Epk            6

Silica        25.6

Whiting    15.1

Zinc         12.1


total:    100


titanium          5

copper carb   5


(Glaze calc done with Insight)

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  • 6 years later...
On 4/17/2014 at 9:00 AM, clay lover said:

I need to make anew bucket of a glaze I have used with good results that used soda feldspar .  Since I have 0 experience in reformulating glazes, which feldspar do you recommend I start testing with that will make the fewest changes?

Custer would be common, neph sy would be common with sodium and has very low si:al I believe, so easy to design low and midfire recipes with.

Edited by Bill Kielb
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Can anyone recommend a small gas kiln brand. I have seen the olympic gas/raku kiln at clayking at around $1400. 3+ cu ft. I'm adding this to my studio that I use skutt electric, but would like to do some cone 10 gas and raku as well. I will appreciate any suggestion or ideas that anyone has before making a purchase. Thank You so much in advance. The Olympic is an updraft, couldn't find a downdraft in that size range, any ideas??

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@Deena The round Olympic updraft kilns are problematic for doing cone 10 reduction. If you search 'conversion' kilns here on the forum, you'll see all the issues people have with that type of kiln, which is just an electric kiln body with burners underneath. People try doing this with old kiln bodies all the time, and realize that they don't fire evenly and often struggle to reach temperature. There are a couple of designs that use an internal downdraft flue that works well, though. Nobody sells one like that, you'll have to do the work yourself. Check out THIS BLOG.

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On 8/3/2020 at 10:50 AM, Deena said:


I built my conversion with the help of that blog.

The design is friggin fantastic, works amazingly well.

Consider keeping a seperate junkier kiln for Raku. 

I don't even like opening the lid on my conversion when it's cooled, opening it hot, would cause more shifting and cracking of the internal flue than I could stand thinking about. Plus it's kinda dangerous.

Check OfferUp for used bodies. I have $50 into the body, $70 into the flue shelf, and about a thousand on shelves and furniture. Borrowed burner probly around $100.



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