Min Posted December 18, 2023 Report Share Posted December 18, 2023 13 hours ago, Denice said: so I need 50 lbs of custar Custer is a potash spar, that means there is more potassium than sodium in the spar. Kona F-4 is a soda spar, it has more sodium than potassium. I for sure would hold on to the Custer given the recent closure of the mine. Kona F-4 hasn't been available for a few years, its replacement is Minspar 200 which works as a 1:1 replacement for Kona F-4. I tend to hold onto materials, never know when you will need something if trying out new recipes or if something becomes obsolete. Quote Link to comment Share on other sites More sharing options...
Mark C. Posted December 18, 2023 Report Share Posted December 18, 2023 I heard (not comfirmed )that Pacer (they mine custar) is going thru bankruptcy and may once again come out as a working mine over time. I now have enough Custar to last me until I'm gone I have a bag or two of the Kona F4 soda spar as well . Good to be a horader of glaze materials Quote Link to comment Share on other sites More sharing options...
Denice Posted December 18, 2023 Report Share Posted December 18, 2023 I tend to hold on to materials also, The soda feldspar was buried under other bags of clay, I think I am going to keep it. Who knows when I might go on a glazing binge, right now I am experimenting with slips. I do a lot of testing before I make anything, I guess I work in reverse to most potter. I have the glaze and clay tested and selected before I make the pot it goes on. Denice Quote Link to comment Share on other sites More sharing options...
Mark C. Posted December 27, 2023 Report Share Posted December 27, 2023 So Laguna is the importer for Mahavir spar and thats the new go to spar to replace Custar read about the breakdown analysis below you can also find this at Laguna's website under articles https://www.lagunaclay.com/_files/ugd/e5330f_f36857d85c574abc9da8e88c9d6fde7b.pdf Quote Link to comment Share on other sites More sharing options...
Min Posted December 27, 2023 Report Share Posted December 27, 2023 @Mark C., do you have a date for when that link came out? In a post a few back, near the bottom of the last page of this thread @Ron Roy is saying "Laguna has said they will not import Haviar spar again." Quote Link to comment Share on other sites More sharing options...
Mark C. Posted December 27, 2023 Report Share Posted December 27, 2023 No i do not but they did stop importing it back then ,but I heard they got it going again since the Custar deal went south-all rumors at this point. IKts cheaper than the EU stuff for them. I know someone who knows more that I will see in about 2-3 weeks I'll ask then. Callie Beller Diesel and Min 2 Quote Link to comment Share on other sites More sharing options...
GEP Posted January 2 Report Share Posted January 2 Hi to all those smarter at glaze chem than me, How do you all feel about subbing Cornwall Stone for Custer or G200? Here's an analysis of "new" Cornwall Stone, which appears to be very similar to "old" Custer (according to Ron Roy's 2000-2012 numbers above). The Cornwall Stone is short on potassium, at 3.34% vs. 7.52% in Custer. Cornwall Stone seems to be available and plentiful. I'm trying to develop a new liner glaze, and want to prioritize long term availability in materials. The recipe I'm interested in is a glossy base from MC6G. My local supplier does not carry G200EU, so I'm wondering if Cornwall Stone would be close enough. MC6G Glossy Base Glaze 1 20 - G200 Feldspar (can I sub Cornwall Stone here?) 20 - Frit 3134 10 - Wollastonite 20 - EPK 11.5 - Talc 18.5 - Silica Quote Link to comment Share on other sites More sharing options...
Min Posted January 2 Report Share Posted January 2 Is the Cornwall analysis from Ceramics Technical 2011 by Jeff Zamek? If so is that the formula from your supplier? Also, which talc do you have? Quote Link to comment Share on other sites More sharing options...
Callie Beller Diesel Posted January 2 Report Share Posted January 2 After checking this article from digitalfire, it looks like actual Cornish stone stopped being available in 2014 or so, but there are a number of substitutes. So it’ll be worth checking into which substitute this is before deciding on long term availability. Some of those substitutes were made by combining other feldspars and if Custer was one of the ingredients, that could still present a problem. In general, Cornwall stone isn’t as strong a melter as feldspar, and a straight 1:1 substitution isn’t going to work well at cone 6. You might need to add a bit more frit, or adjust with a touch of neph sye, depending. Cornwall stone also has some phosphorous in it, which can make for some neat colour responses/reactions. But it can also flocculate your glaze. Because I think you’re likely not looking for potassium to provide a specific colour response, you could try subbing another feldspar that has a combined sodium and potassium number that’s closer to Custer’s combined values (KNa). The silica and alumina numbers will be less important to match in your substitution candidate, as you can adjust silica or EPK numbers in this recipe to compensate. GEP 1 Quote Link to comment Share on other sites More sharing options...
GEP Posted January 2 Report Share Posted January 2 1 hour ago, Min said: Is the Cornwall analysis from Ceramics Technical 2011 by Jeff Zamek? If so is that the formula from your supplier? Also, which talc do you have? Yes, the Cornwall data is from Jeff Zamek 2011 article. The one my supplier is carrying is a Laguna product, and described as “Apparently the same as original Cornwall Stone but we recommend testing.” I am assuming this is the same one as Zamek’s analysis, but could be wrong. I have some FABI Talc and plan to do any further glazemaking with it. Quote Link to comment Share on other sites More sharing options...
GEP Posted January 2 Report Share Posted January 2 (edited) 36 minutes ago, Callie Beller Diesel said: After checking this article from digitalfire, it looks like actual Cornish stone stopped being available in 2014 or so, but there are a number of substitutes. So it’ll be worth checking into which substitute this is before deciding on long term availability. Some of those substitutes were made by combining other feldspars and if Custer was one of the ingredients, that could still present a problem. In general, Cornwall stone isn’t as strong a melter as feldspar, and a straight 1:1 substitution isn’t going to work well at cone 6. You might need to add a bit more frit, or adjust with a touch of neph sye, depending. Cornwall stone also has some phosphorous in it, which can make for some neat colour responses/reactions. But it can also flocculate your glaze. Because I think you’re likely not looking for potassium to provide a specific colour response, you could try subbing another feldspar that has a combined sodium and potassium number that’s closer to Custer’s combined values (KNa). The silica and alumina numbers will be less important to match in your substitution candidate, as you can adjust silica or EPK numbers in this recipe to compensate. I’m trying to make a white glaze, so you’re right that an exact color response is not that important to me. My supplier is only offering Minspar and Plastic Vitrox Clay, as far as feldspars go. Plus the Cornwall, which they do not classify as a feldspar exactly. My needs are to find a reliable recipe that I can make in large quantities on a regular basis, so buying 50lb sacks online and shipped to me is not feasible. I need to work with what my local supplier has. I like the idea of subbing Cornwall, but upping the Frit to boost the melting. Edited January 2 by GEP Quote Link to comment Share on other sites More sharing options...
Min Posted January 2 Report Share Posted January 2 26 minutes ago, GEP said: The one my supplier is carrying is a Laguna product, and described as “Apparently the same as original Cornwall Stone but we recommend testing.” I am assuming this is the same one as Zamek’s analysis, but could be wrong. If your supplier carries other Laguna products then it could well be but not for certain. If you could confirm this that could help. I'll have a go at running the recipe with that analysis and tweaking it to match as close as I can to the original. Quote Link to comment Share on other sites More sharing options...
Min Posted January 2 Report Share Posted January 2 Three recipes below, original in the first one using Amtalc since a specific one wasn't specified. Second recipe shows what the formula would look like just doing a direct substitute of Cornwall Stone for the G200 and Fabi talc for the Amtalc. Third recipe is one where the oxides are as balanced as I can get them without adding another material. Only change to formula in recipe 3 is potassium and sodium amounts are different when looked at separately but equivalent when looked at when the two oxides are combined. (KnaO figure) Given you are testing this for your liner I don't think this will make a difference. Main difference is far more Cornwall is needed to supply the sodium and potassium than the G200 supplied. This extra Cornwall bumped the overall silica up so that needed to be reduced by subtracting silica. Same for alumina hence the small drop in EPK. Other oxides just needed minor tweaking. Silica to alumina ratio is the same in 3rd version, COE is pretty close, this will be a minor fraction of a decimal difference, not significant. I left the total for recipe 3 at 99.30 to keep the material amounts in whole numbers or just going into the tenths. If you try this please just do a small test amount first, what looks good on paper doesn't always translate to the pot. Hulk, Callie Beller Diesel and GEP 3 Quote Link to comment Share on other sites More sharing options...
GEP Posted January 2 Report Share Posted January 2 (edited) 49 minutes ago, Min said: If your supplier carries other Laguna products then it could well be but not for certain. If you could confirm this that could help. I'll have a go at running the recipe with that analysis and tweaking it to match as close as I can to the original. The listing on my supplier’s website is “Cornwall Stone - Laguna Blend” so I’m pretty sure it is the Laguna product. I will email them tomorrow (need to ask them some other questions anyways) and confirm where it’s from. THANK YOU for the adjusted recipe!! Edited January 2 by GEP Quote Link to comment Share on other sites More sharing options...
Mark C. Posted January 3 Report Share Posted January 3 True Cornwall has been gone for a long time The Laguna cornwall blend has been around a long time as well -its breakdown is here https://www.axner.com/cornwall-stone-laguna-substitute.aspx GEP 1 Quote Link to comment Share on other sites More sharing options...
Min Posted January 3 Report Share Posted January 3 Thanks for the link Mark, the analysis is different for the Laguna blended Cornwall substitute. This could make a difference! @GEP, I'll redo the recipe using the Laguna analysis. I'll run it with PV also since you have that available too. GEP 1 Quote Link to comment Share on other sites More sharing options...
Min Posted January 3 Report Share Posted January 3 Okay, using Laguna analysis not the Jeff Zamek 2011 article analysis (plus subbing Fabi Talc) I came up with the third recipe below. @GEP, I would confirm with Laguna that info is still correct. Second recipe is a 1 to 1 swap of both Cornwall sub and Fabi Talc, it needed some tweaking. Laguna Cornwall sub is up but not by nearly as much as with the Zamek analysis, silica is up and the rest just minor tweaks. Again the sodium + potassium is a combined value. I think Callie brought up a very important aspect, if Laguna is using Custer spar as part of the Cornwall sub blend then this could throw a wrench in the works going forward. Don't know if they use it or not, anybody's guess at this point. To keep this from getting too confusing I'll add a PV version in a separate post. GEP and Callie Beller Diesel 2 Quote Link to comment Share on other sites More sharing options...
Min Posted January 3 Report Share Posted January 3 Plastic Vitrox (PV) version of GB1 using Fabi Talc. (why do I keep thinking that as Fabio talc? lol) I know PV can vary a fair bit but went with Insight analysis. Had to supply the calcium from calcium carb in place of wollastonite as the silica was too high using the latter. GEP and Callie Beller Diesel 2 Quote Link to comment Share on other sites More sharing options...
GEP Posted January 3 Report Share Posted January 3 These are awesome @Min! Thank you so much!! And thank you @Mark C. for the breakdown of Laguna Cornwall. Well, at least in my studio, I’m gonna call it Fabio Talc from now on :-) Quote Link to comment Share on other sites More sharing options...
GEP Posted January 3 Report Share Posted January 3 (edited) I spoke to my local supplier, they did not have any info about the ingredients used to make Cornwall Stone, and they said availability seems good. They suggested I check with Laguna, so I gave them a call. The tech I spoke to said that their Cornwall Stone blend does not use Custer Feldspar. He declined to tell me which feldspar was used (it is 65% of the total) but assured me that it was not going out of production anytime soon. So it seems that Cornwall Stone Laguna Blend is plentiful, and can be a reasonable substitute for Custer Feldspar. More good news from my local supplier... all the Ferro Frits are plentiful again. That was not the case during the pandemic. Edited January 3 by GEP Quote Link to comment Share on other sites More sharing options...
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