Bill Kielb Posted January 7 Report Share Posted January 7 30 minutes ago, Bam2015 said: Maybe I have no business making my own glaze if the info in this thread is way over my head. Not to worry, folks have made glazes forever and experimented looking for predictable ways to characterize what happens. They publish their findings or research and you get to decide if it is useful to you. Commercial glazes have the issue of - what is in them and how does one correct a defect such as crazing. The good part is commercial glazes don’t use lead anymore (for the most part), vanadium pentoxide etc… generally because someone found out it was a bad thing. If you mix your own then you know what is in it and can reasonably test for durability, fit, etc…. to your satisfaction, before selling it or giving it as a present for human consumption. I think it does help to inform but definitely not for everyone. Hulk and Min 2 Quote Link to comment Share on other sites More sharing options...
Hulk Posted January 7 Report Share Posted January 7 (edited) Commercial glazes, err, some commercial glazes may contain less expensive ingredients and/or behave poorly. Less behaved glazes may: settle quickly, crawl, craze, pinhole ...have washed out color (especially where expensive colorants are involved) ... etc. When looking for recipes, starting out*, a few ideas (which I'd found here, in this Forum, and a few other places**) were helpful: from a reputable source; with helpful notes on application, durability, and heavy metal leach testing results; with pictures! I just picked several recipes, made a materials list, and went shopping***! From there, learned, err, learning from successes, failures/mistakes, and more reading. ...and thanks to several Forum regulars for insight and assistance. *Coming up on six years ago, how time flies **Digitalfire.com, a trove of information; the glaze recipe book at local JC ceramic lab (we were using the glazes - direct experience!); Petersen's book The Craft and Art of Clay; Van Gilder's book Wheel-Thrown Pottery; and several other books, magazines, and web pages. Oh, web pages! ...Hesselberth's website can still be found, FrogPondPottery, Tested Glazes | Frog Pond Pottery (archive.org) Lakeside Pottery also has glazes sub-pages with pictures and notes... ***took the pickup truck, packed the load up against the front of the bed and tied it down tight, some twelve hundred pounds of clays and glaze materials... Edited January 8 by Hulk lists and sublists, commas and semicolons, + a credit Callie Beller Diesel and Bill Kielb 2 Quote Link to comment Share on other sites More sharing options...
Callie Beller Diesel Posted January 7 Report Share Posted January 7 7 hours ago, Bam2015 said: this thread is way over my head. This thread is getting more complex than it needs to be, certainly. It has ceased to be about helping the OP, and more about people arguing fine points of technical knowledge. I’m going to suggest that the tech heads start a new thread about the comparative merits of Stull’s and Katz’s work if they want to keep going in that direction. Any further replies on this one should try to focus on helping @GEP find a practical solution to her problem, which is needing a good base glaze for her work that doesn’t need recently discontinued materials. Bam2015 and Kelly in AK 2 Quote Link to comment Share on other sites More sharing options...
Callie Beller Diesel Posted January 7 Report Share Posted January 7 @Bam2015 don’t let this thread overwhelm you too badly. If you want to zoom out far enough, no glaze will be as good as the day it was fired in a thousand years. They’ll all break down eventually. While it’s possible to get really granular about the chemistry, it’s also worth noting that there’s also a pretty wide range of things that can be considered durable. The “good enough” threshold has at least some flex in it. And chemistry isn’t the only factor: the entire firing cycle is at work, as well as any interactions with the clay body itself. We use tools like Stull maps, glaze calc software or limit formulas to help reduce some empirical testing, but it doesn’t eliminate the need for at least some due diligence test tiles. And that holds true with commercial clear glazes too. At some point you have to pick a recipe to mix, apply it to a pot and find out. Magnolia Mud Research 1 Quote Link to comment Share on other sites More sharing options...
neilestrick Posted January 7 Report Share Posted January 7 8 hours ago, Bam2015 said: This post is truly mind boggling to me. I know that glaze chemistry is complex, but this thread now makes me question if I should just buy commercial clear glaze rather than make my own because I might be creating an end product that is neither durable nor safe over time. Maybe I have no business making my own glaze if the info in this thread is way over my head. The things being discussed here is are not necessary to good glaze formulation. I've been making durable glazes for 30 years without ever looking at a Stull chart or Katz's papers. Learning the basic of glaze formulation- fluxes, stabilizers, and glass formers- will serve you just fine, and allow for tweaking formulas to increase durability and adjust glaze fit for your clay body. Commercial glazes are not necessarily any more durable. They all take testing as well. Clear glazes are generally quite safe if they're free of lead and cadmium, which most all glaze recipes being used nowadays are, and they don't have the heavy metals (colorants) in them that are likely to leach in a poorly formulated glaze. The benefits of mixing your own glazes are that they are much less expensive, and you can alter them as needed to fit the clay body you're using. If you know another potter that has a good clear glaze, by all means ask them for a recipe. Kelly in AK, Magnolia Mud Research, Roberta12 and 2 others 5 Quote Link to comment Share on other sites More sharing options...
Bam2015 Posted January 8 Report Share Posted January 8 (edited) I did not mean to take this thread down a different path but appreciate the responses. Mea, hopefully this thread will result in a new glaze formulation for you. Betty Edited January 8 by Bam2015 Hulk 1 Quote Link to comment Share on other sites More sharing options...
C.Banks Posted January 8 Report Share Posted January 8 (edited) On 1/7/2024 at 5:20 AM, Bam2015 said: Maybe I have no business making my own glaze if the info in this thread is way over my head. There is old criticsm of certain aspects of glaze chemstyr as being overly complicated and a bit elitist - the UMF system in particular. Some of the most sucessful potters I've known grew up on a healthy diet of 'melt and see'. They wasted some time, energy and materials over time I imagine but we did just fine for our purposes. There is obvious value in the UMF but please don't let the language muffle your curiosity. Edited January 8 by C.Banks Magnolia Mud Research 1 Quote Link to comment Share on other sites More sharing options...
High Bridge Pottery Posted January 8 Report Share Posted January 8 Everybody starts off way over their head with glaze chemistry. I have been chatting about glazes on here for 10 years and I still feel things flying over my head. I find frit and clay glazes much easier to work with and control. You do have to add flocc/deflocc and possibly a binder to dial in the working properties but it is better than having raw materials bring variable qualities to the glaze slip. The fired result may be better or worse using frit but on getting the glaze onto pottery I like a simple glaze. Quote Link to comment Share on other sites More sharing options...
Min Posted January 8 Report Share Posted January 8 3 hours ago, C.Banks said: There is old criticsm of certain aspects of glaze chemstyr as being overly complicated and a bit elitist - the UMF system in particular. How so? I have started a new thread covering Stull, ratios etc here, might be best to reply in that thread to avoid this one going off topic. Quote Link to comment Share on other sites More sharing options...
ChristopherW Posted January 19 Report Share Posted January 19 Hello, Is this glaze stable? It is a similar recipe to the one in this thread. Gerstley Borate 50 Silica 30 EPK 20 Thank you... Quote Link to comment Share on other sites More sharing options...
Hulk Posted January 19 Report Share Posted January 19 That glaze formula (ChristopherW, above) is within two percentage points of "Functional Clear" glaze (cone 5/6) that was available in a Studio setting where I started out. It went on well*, melted well - glossy, smooth, fit the clays, nice! ...however, I'm not seeing that it's particularly durable. The wares that have seen regular** use, the glaze failed, hence the wares were retired. I'm using a liner glaze that has much less boron, more silica and alumina, low coefficient of expansion... A nod to Forum regulars that provided feedback, observations, and formulation suggestions when I was looking to fit a liner glaze. I ended up abandoning a few (at least four) formulations and adjusted what I'm using now several times. *After thorough stirring, I'd ladle some out to a clean container, sieve it, check specific gravity, adjust the thixotropy, glaze my ware, then dump the glaze back into the communal bucket. **The wares that see occasional use and are otherwise "babied" by hand wash with mild soap and No Soaking are still looking good. Quote Link to comment Share on other sites More sharing options...
Min Posted January 19 Report Share Posted January 19 @ChristopherW, I would not expect the recipe you posted to make a durable glaze. (but it will be a very expensive glaze to mix up given the price of Gerstley Borate now) Callie Beller Diesel 1 Quote Link to comment Share on other sites More sharing options...
Bam2015 Posted January 19 Report Share Posted January 19 3 hours ago, Hulk said: I'm using a liner glaze that has much less boron, more silica and alumina, low coefficient of expansion.. Hulk, are you willing to share this recipe? Or maybe you already did and I overlooked it. Thank you! Quote Link to comment Share on other sites More sharing options...
ChristopherW Posted January 19 Report Share Posted January 19 Appreciate replies! As the thread title suggests.....does anyone have a simple cone 6 clear glaze recipe to share?! I understand if someone doesn't want to post the recipe, for various reasons! Particularly, is there a simple clear using Gerstley Borate that someone thinks is stable? Appreciate.... Quote Link to comment Share on other sites More sharing options...
Bill Kielb Posted January 20 Report Share Posted January 20 (edited) @ChristopherW Ok I’ll take a shot. This was a favorite in 2018 and has been tested and used for a studio clear for several years I know of. Samples in dishwasher forever. Actually moved to new dishwasher as old one wore out. Test piece going on approx 800 wash cycles. It’s Gerstley so not so much a favorite anymore. Glazes often don’t travel well but you are welcome to it. Hope it works for you. This is one of those glazes developed taking the Katz course. The spreadsheet is his, but we have written permission by him to automate the sheet and redistribute. I think he has a new free excel sheet as well. Don’t forget use the 100% batch column. Edited January 20 by Bill Kielb akilpots, GEP and Roberta12 3 Quote Link to comment Share on other sites More sharing options...
akilpots Posted January 20 Report Share Posted January 20 I've been working on this simple cone 6 glossy base using the cheapest materials at my supplier. also developed during matt katz's course. https://glazy.org/recipes/420048 GEP and Bill Kielb 2 Quote Link to comment Share on other sites More sharing options...
Hulk Posted January 20 Report Share Posted January 20 11 hours ago, Bam2015 said: Hulk, are you willing to share this recipe? See 10-SEP-2020 update, second recipe, "Min's low expansion III" Clay composition and crazing - Page 2 - Clay and Glaze Chemistry - Ceramic Arts Daily Community I mix and sieve it, setting specific gravity to about 1.42, then adjust the thixotropy as needed*. I like the glaze, having tried, adjusted, then abandoned several clear/clearish liner glazes before getting this one sorted. Playing around with new recipes in coming years, likely, for my bag of Gerstley Borate will one day be empty, also the bag of Texas talc, and smaller sack of Petalite. *I'm stirring clockwise at a repeatable speed. Once the whisk is removed, I expect to see the mass of glaze revolving together at the same speed, for about three or four turns before coming to a stop, all together, and "bouncing back" a little bit. Glaze that's not sufficiently "gel" will spin much longer, with several currents running at different speeds. See Tony Hansen's article and video clip Thixotropy and How to Gel a Ceramic Glaze (digitalfire.com) Roberta12 1 Quote Link to comment Share on other sites More sharing options...
Min Posted January 20 Report Share Posted January 20 Appreciate the people who have shared their recipes for a clear glaze. Getting a well fitting clear is one of the harder glazes to come up with. For those new to mixing their own glazes, be sure to test the glaze for FIT before making up a big bucket. Glaze fit to a claybody is no different than fitting a pair of jeans. What fits my body won't necessarily fit everyone else's body. If you use a high expansion glaze on one side of a pot and a low expansion one on the other there is a good chance of the pot dunting / cracking. If someone is looking for a clear glaze to use with or over stains or underglazes or some specific colouring combinations (like chrome tin pinks, reds, purples etc) then you need a specific type of clear glaze that is hospitable to the colourants. Roberta12, Kelly in AK, Hulk and 2 others 5 Quote Link to comment Share on other sites More sharing options...
Harold Roberts Posted January 22 Report Share Posted January 22 This is a clear glaze that I use, fairly simple and if you add 8% rutile it becomes a beautiful white gloss. Oyster Gloss EPK –--------------------- 6 Dolomite –------------- 12 Gerstley Borate ----- 23 Flint –-------------------- 27 Nephelene Syenite - 32 And another clear using less Gerstley Borate. Gloss EPK –----------------------- 6 Dolomite –-------------- 12 Gerstley Borate –----- 12 Flint –--------------------- 30 Nephelene Syenite -- 40 Hulk 1 Quote Link to comment Share on other sites More sharing options...
ChristopherW Posted January 22 Report Share Posted January 22 Super appreciate...! Quote Link to comment Share on other sites More sharing options...
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