{"id":122,"date":"2012-07-20T11:24:23","date_gmt":"2012-07-20T15:24:23","guid":{"rendered":"http:\/\/lindaarbuckle.com\/lindaarbuckle-blog\/?p=122"},"modified":"2012-07-20T11:26:42","modified_gmt":"2012-07-20T15:26:42","slug":"feldspar-changes","status":"publish","type":"post","link":"https:\/\/www.lindaarbuckle.com\/lindaarbuckle-blog\/feldspar-changes\/","title":{"rendered":"Feldspar changes"},"content":{"rendered":"

Somone just asked me about a spar substitution. My experience is that for many \"\"applications, spar substitutions within the categories of soda spars or pot (potassium) spars have some leeway and will often endure substitutions fairly easily. Unless they don’t. The “pot” or “soda” spar refers to the dominant flux in the feldspar. I suggest testing, and I’d test the easiest fix first – substitute a spar you have, and see if it changes things in an unacceptable way. If it does, try the things suggested below. At home I’m still slogging through my big bucket of old majolica glaze. At workshops, I’ve had people use various substitutions, and other than some alternate soda spars deflocculating\u00a0the raw\u00a0glaze, it’s been fine. If you need to review floc\/deflocc, see the\u00a0 Ceramic Arts Daily video demo on this<\/a>.<\/p>\n

feldspar <\/strong>Idealized formula KNaO\u2022 Al2<\/sub>O3<\/sub>\u2022 6SiO2<\/sub><\/p>\n

In the idealized (simplified) feldspar formula above, KNaO refers to any combination of sodium or potassium. K2<\/sub>O is potassium oxide – 2 potassium for every oxygen. Ditto Na2<\/sub>O. So KNaO\u00a0maintains the 2 units of flux for every oxygen, but is shorthand for “any combination of” because they often operate interchangably\u00a0and it’s easier to calculate if you overlook the distinction because if often doesn’t matter. An actual feldspar, say F4, will have traces of other oxides in it, and not\u00a0be quite that simple. These small inclusions are often overlooked in calculation of glazes because they often are insignificant. Since sodium and potassium have different atomic weights, the weights of soda spar and pot spar differ in idealized form. If you plug in\u00a0two K instead of KNaO, the weight is 556 units vs.\u00a0524 for sodium. So, you might get a weight difference if you jump pot vs. soda categories. It would be conservative to stay within K or Na family of the spar you’re substituting. Wikipedia on feldspar<\/a>. Image from Wikipedia.<\/p>\n

Info below thanks to NM Clay in 2010.\u00a0 If you go to Brant’s blog post below, you can download the datasheets for the spars.
\nhttp:\/\/nmclay.blogspot.com\/2010\/02\/changes-in-feldspar-scene.html<\/a><\/p>\n

Soda Feldspar – Kona F4<\/strong>\u00a0There is a supply change in the Soda Feldspar Kona F4. It is not available from the mine any longer due to a fire and mine closure. We will have Minspar\u00a0200 available. They are both very close to the F4 in composition. A chemical analysis of the materials is below.<\/p>\n\n\n\n\n\n\n\n\n\n\n\n
\u00a0<\/strong>Minspar 200 Feldspar<\/strong><\/strong><\/td>\n\u00a0<\/strong>Kona F-4 Feldspar\u00a0\u00a0 <\/strong>Sodium Feldspar<\/strong><\/strong><\/td>\n<\/tr>\n
CaO 1.50<\/td>\nCaO 1.70<\/td>\n<\/tr>\n
~~~<\/td>\nMgO 0.05<\/td>\n<\/tr>\n
K2O 4.10<\/td>\nK2O 4.80<\/td>\n<\/tr>\n
Na2O 6.50<\/td>\nNa2O 6.90<\/td>\n<\/tr>\n
Al2O3 18.50<\/td>\nAl2O3 19.60<\/td>\n<\/tr>\n
SiO2 68.60<\/td>\nSiO2 66.80<\/td>\n<\/tr>\n
Fe2O3 0.06<\/td>\nFe2O3 0.04<\/td>\n<\/tr>\n
Volatiles % LOI 0.30<\/td>\nVolatiles %\u00a0 \u00a0 LOI 0.20<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Minspar 200 was Formerly NC-4 Feldspar.<\/p>\n

G200\u00a0update From Jeff Zamek Article from Ceramics Technical (November 1, 2009)<\/p>\n

\u201cG-200 felspar, mined by Imerys\u00a0North America Ceramics, has been discontinued. While there are still stocks in potters’ studios and ceramics supply bins it will eventually join Albany Slip, Gerstley\u00a0borate, Kingman felspar, Oxford felspar, and other materials that have gone out of production. G-200’s\u00a0demise is based on economic considerations that potters do not control. Originally, G-200, as potters know it, was blended at the processing plant by using 70% Minspar 200, a sodium based felspar, and 30% HP G-200, a potassium based felspar. The blended felspars then became G-200 and were shipped throughout the United States.<\/p>\n

The increasing costs of shipping Minspar 200 from Spruce Pine, NC and G-200 HP, mined in Siloam, GA, to the processing plant in Monticello, GA, a trip of over 200 miles, made this situation uneconomical. Potters are now faced with either using Custer feldspar in place of or finding a new potassium based felspar.\u201d<\/p>\n

Thank you Mr. Zamek I couldn\u2019t have said it better or at all!<\/p>\n

Laguna Clay will be blending G-200 so it will be available. G-200HP\u00a0is the new product and according to Jon Pacini\u00a0from Laguna the major difference is slightly more fluxing power, similar to (the also defunct) Kingman Feldspar of old.<\/p>\n

Posted by Brant from New Mexico Clay Inc<\/a>\u00a0on his blog.<\/p>\n

 <\/p>\n

 <\/p>\n","protected":false},"excerpt":{"rendered":"

Somone just asked me about a spar substitution. My experience is that for many applications, spar substitutions within the categories of soda spars or pot (potassium) spars have some leeway and will often endure substitutions fairly easily. Unless they don’t. The “pot” or “soda” spar refers to the dominant flux in the feldspar. I suggest… Continue reading Feldspar changes<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":false,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[3,1],"tags":[],"class_list":["post-122","post","type-post","status-publish","format-standard","hentry","category-ceramic-tech-info","category-uncategorized","entry"],"aioseo_notices":[],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/p2xO7A-1Y","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/www.lindaarbuckle.com\/lindaarbuckle-blog\/wp-json\/wp\/v2\/posts\/122","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.lindaarbuckle.com\/lindaarbuckle-blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.lindaarbuckle.com\/lindaarbuckle-blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.lindaarbuckle.com\/lindaarbuckle-blog\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.lindaarbuckle.com\/lindaarbuckle-blog\/wp-json\/wp\/v2\/comments?post=122"}],"version-history":[{"count":9,"href":"https:\/\/www.lindaarbuckle.com\/lindaarbuckle-blog\/wp-json\/wp\/v2\/posts\/122\/revisions"}],"predecessor-version":[{"id":131,"href":"https:\/\/www.lindaarbuckle.com\/lindaarbuckle-blog\/wp-json\/wp\/v2\/posts\/122\/revisions\/131"}],"wp:attachment":[{"href":"https:\/\/www.lindaarbuckle.com\/lindaarbuckle-blog\/wp-json\/wp\/v2\/media?parent=122"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.lindaarbuckle.com\/lindaarbuckle-blog\/wp-json\/wp\/v2\/categories?post=122"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.lindaarbuckle.com\/lindaarbuckle-blog\/wp-json\/wp\/v2\/tags?post=122"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}