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Mark (Marko) Madrazo

Feldspar G-200

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G-200 and its replacement, G-200HP, are no longer available. You can do a blend of Minspar 200 (soda spar) and Custer (potash spar).

 

http://www.clayworkssupplies.com/tech-info/ti_file1234374884.pdf

 

https://www.highwaterclays.com/index.cfm?fuseaction=feature.display&feature_ID=306

Wow, thanks bciskepottery. I will try the custer. I do a test batch before I commit to my 5000g batch I have already waiting this final element. Thanks for the PDF's I'll keep them in my glaze records binder. 

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This is the same formula using Custer:

Ferro 3134          999

Custer                1048

EPK                    1010

Talc                      586

Wollastonite         510

Silica                    848

 

Total                  5001 grams

 

David

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Well, actually, Marko, Bruce, and David, there is another wrinkle. The G200 mine ran out a long time ago. It was replaced by G200HP (higher in potash), but a comparable material could be created by blending 70% G200HP and 30% Minspar. But then the G200HP mine ran out last year. So cancel that idea. At the time, the old G200 was very close to Custer, so some people just used Custer instead. However, a few years ago, the Custer product changed significantly. Pacer (the producer of Custer) denies there was any change, but potters noticed their glazes were not working properly and independent lab tests revealed that any Custer in the last 2-3 years is lower in potash and higher in silica, thus causing glazes with significant proportions of Custer to underfire. Ron Roy has written about this, and John H. has reformulated some of the glazes in their book. Here is a link to the revised Glossy Base 1 recipe using the new, lower potash Custer: http://www.masteringglazes.com/mastering-cone-6-glazes/glaze-reformulations/chapter-6-glaze-reformulati/glossy-base-1-new-custer.html

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Well, actually, Marko, Bruce, and David, there is another wrinkle. The G200 mine ran out a long time ago. It was replaced by G200HP (higher in potash), but a comparable material could be created by blending 70% G200HP and 30% Minspar. But then the G200HP mine ran out last year. So cancel that idea. At the time, the old G200 was very close to Custer, so some people just used Custer instead. However, a few years ago, the Custer product changed significantly. Pacer (the producer of Custer) denies there was any change, but potters noticed their glazes were not working properly and independent lab tests revealed that any Custer in the last 2-3 years is lower in potash and higher in silica, thus causing glazes with significant proportions of Custer to underfire. Ron Roy has written about this, and John H. has reformulated some of the glazes in their book. Here is a link to the revised Glossy Base 1 recipe using the new, lower potash Custer: http://www.masteringglazes.com/mastering-cone-6-glazes/glaze-reformulations/chapter-6-glaze-reformulati/glossy-base-1-new-custer.html

Dick nailed it as custer did change a few years back.

One way to fix these changes is buy a large quantity of whatever material you use -then these changes do not affect you.I'm still working with 3,000#s of Kingman potash feldspar I bought in 1981.

Mark

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Holly Molly guys, this is more an answer than I expected, but I am so grateful. I am really green when it comes to glaze mixing. I wouldn't have know these things if you good people didn't help me. It's a lot to look at but It's what I want if I ever expect to really understand ^6 glazes. Hell, pottery for that matter.

 

I join DigitalFire, but I can't understand it enough to make good practical use of it. I guess I should query Tony or you folk on some questions about it. I'm sure I can learn it, I just need to commit more time to it. 

 

I do have custer, but no minspar. My supplier, www.clayworld.com does not seems to have it. Is there a substitute for this also, or is it under a different name? My supplier has G200HP, so I got a 50# bag. 

 

In this recipe I show, I have already put everything in the 5gal bucket before I realized I did not have any G200. Can I just add the G200HP. I don't want to throw out all the chemical I already added. I guess I should have checked that I did indeed have enough. What can I say, just a newby.  :blink:

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Hi Mark,

All you need to do is add 990 grams of G200 HP to the batch and 10 grams  more of EPK.. The new 5K batch is as follows:

Ferro 3134     1000

G 200 HP         990

EPK                1010

Talc                  575

Wollastonite     500

Silica                925

David

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Hi Mark,

All you need to do is add 990 grams of G200 HP to the batch and 10 grams  more of EPK.. The new 5K batch is as follows:

Ferro 3134     1000

G 200 HP         990

EPK                1010

Talc                  575

Wollastonite     500

Silica                925

David

Thank you David, you are my hero. I really appreciate it. I do not know how you figure these things out, but I'm glad you are so kind and generous. I'm also glad I waited for an answer. And I promise I will try and learn this stuff better and make sure I test and have enough to make a bucket. Thanks again David. I will sleep better tonight and get this done tomorrow.  :D

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This is the same formula using Custer:

Ferro 3134          999

Custer                1048

EPK                    1010

Talc                      586

Wollastonite         510

Silica                    848

 

Total                  5001 grams

 

David

Thanks for this one. I will keep it since, as I understand, G200HP might run out. Thumbs up!

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Hi Mark,  Because of changes in Custer the following should be considered but I would test with 100 gram batches first.

Ron Roy average Custer                          Insight Custer                   G200HP

Ferro 3134       1000                                  1000                               1000

Custer Ave        1235                                  1050                 G200HP  990         

EPK                    990                                   1010                               1010      

Talc                    575                                     575                                 575

Wollastonite        510                                     510                                 500                

Silica                   690                                     855                                 925

 

Good luck David

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Hi Mark,  Because of changes in Custer the following should be considered but I would test with 100 gram batches first.

Ron Roy average Custer                          Insight Custer                   G200HP

Ferro 3134       1000                                  1000                               1000

Custer Ave        1235                                  1050                 G200HP  990         

EPK                    990                                   1010                               1010      

Talc                    575                                     575                                 575

Wollastonite        510                                     510                                 500                

Silica                   690                                     855                                 925

 

Good luck David

Thanks for all your help, David. Now I hope I get it right. LOL  :D

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