bryandave Posted October 1, 2021 Report Share Posted October 1, 2021 hello everyone i have encounter some questions, would like to ask for help! as you can see, the right hand side is my own glaze(the receipt is below) and the left hand side is amaco SM 11 my question is why my glaze looks so thin and not as buttery as the SM11, i was so obsess with that texture and feel, and i fine tune a lot for my glaze, but still cant get that texture! does anyone know why? how can i get my glaze more buttery tks my receipt silica 26.9 dolomite 23.5 china clay 18.3 3124 17.3 calcined kaolin 13.9 tin 5 Link to comment Share on other sites More sharing options...
Bill Kielb Posted October 1, 2021 Report Share Posted October 1, 2021 What is the basis for this recipe? It appears like not enough boron, assuming cone 6, and lots and lots of clay considering China clay and calcined kaolin.. Is this a recipe you have proven is good for you? It has a fairly non standard flux ratio, that aside it should fire matte by the looks of its si:al ratio and your picture seems to indicate it does that. Normally I would suggest to try: raise the boron to 0.15 for cone six and add silica until it is the desired sheen or feel. I am apprehensive about it because of the flux ratio and with double the clay in it I can’t help get the feeling one of these ingredients should be a feldspar and there is a transcription error in this recipe. Glay recipe UMF below Link to comment Share on other sites More sharing options...
bryandave Posted October 2, 2021 Author Report Share Posted October 2, 2021 9 hours ago, Bill Kielb said: What is the basis for this recipe? It appears like not enough boron, assuming cone 6, and lots and lots of clay considering China clay and calcined kaolin.. Is this a recipe you have proven is good for you? It has a fairly non standard flux ratio, that aside it should fire matte by the looks of its si:al ratio and your picture seems to indicate it does that. Normally I would suggest to try: raise the boron to 0.15 for cone six and add silica until it is the desired sheen or feel. I am apprehensive about it because of the flux ratio and with double the clay in it I can’t help get the feeling one of these ingredients should be a feldspar and there is a transcription error in this recipe. Glay recipe UMF below 9 hours ago, Bill Kielb said: Whoops duplicate hi bill! thanks for the answer, I have revise a bit to my receipt now (see attached ) by adjusting the flux radio and add some more felpspar, see what do you think to my new receipt bryan Link to comment Share on other sites More sharing options...
Bill Kielb Posted October 2, 2021 Report Share Posted October 2, 2021 It’s better, not sure it will work as intended but if you are developing, and you believe it is what you want to try. The alumina is fairly high but it is a matte and ought to be in the 5:1 range. If it fits and you like it then adding silica ( small progressive increments) ought make it less matte. Probably can rid yourself of the calcined kaolin at this point, just a hassle to prepare and at 18% China clay, plenty of clay. Not sure why you picked what you picked but something to test with. From here, dial in or check the fit and adjust silica to desired matte and feel as well as tin for color. Mattes can be a challenge to get a fit, so moving the R2O towards 0.2 while leaving the alumina relatively high to keep your 5 ‘ish si:al ratio is a technique to reduce the COE if this crazes on your clay Link to comment Share on other sites More sharing options...
neilestrick Posted October 4, 2021 Report Share Posted October 4, 2021 Do some searching on the internet, Pinterest, Glazy, etc and you should be able to find a recipe that's very close to what you want. It looks like a pretty typical magnesium matte glaze. Link to comment Share on other sites More sharing options...
bryandave Posted October 8, 2021 Author Report Share Posted October 8, 2021 On 10/2/2021 at 5:22 PM, Bill Kielb said: It’s better, not sure it will work as intended but if you are developing, and you believe it is what you want to try. The alumina is fairly high but it is a matte and ought to be in the 5:1 range. If it fits and you like it then adding silica ( small progressive increments) ought make it less matte. Probably can rid yourself of the calcined kaolin at this point, just a hassle to prepare and at 18% China clay, plenty of clay. Not sure why you picked what you picked but something to test with. From here, dial in or check the fit and adjust silica to desired matte and feel as well as tin for color. Mattes can be a challenge to get a fit, so moving the R2O towards 0.2 while leaving the alumina relatively high to keep your 5 ‘ish si:al ratio is a technique to reduce the COE if this crazes on your clay hi bill i have tried that glaze, and the result turns better now! thanks for the help! but it comes up another questions, is that when i put on ink (try to do a coloring test is if there are any small crackle), you can see there a few crackle on it!, and i have try to add more silica on the receipt, but the result sees not obverious, may i know how can i solve this crackle? or should i add more silica , then they surface may be better? ka Link to comment Share on other sites More sharing options...
Bill Kielb Posted October 8, 2021 Report Share Posted October 8, 2021 More silica will make it smoother but not likely solve the crackle (crazing) which is a glaze fit issue or difference in the coefficient of expansion. COE problems can be tough to solve especially for a matte. Moving the R2O more towards 0.2 while maintaining the relatively high alumina can be a successful technique. Unless you are committed to this recipe for some reason, as Neil said it may be easier just to find one that already works on Glazy or from another source. If you are doing this as part of a learning experience then that is admirable. Here is a nice video that Sue McLeod presented at NCECA a few years back. https://youtu.be/Uf07jOKuW5s it has a lot of Stull and surface indication but near the very end she discusses the reason this technique can work for mattes which really is removing or reducing higher expansion fluxes for lower expansion ones. Glaze chemistry is fairly complex and folks spend many years learning the nuances. Raising the silica will generally transform the glaze from matte (approximately) 5:1 Si:Al to glossy (Approximately) 7:1 Si:Al so along the way the matte becomes more buttery or glossy. Solve the fit problem first, then you can work on the texture pretty easily.. Here is a matte you can try https://glazy.org/recipes/19734 some have great results (four stars) and others hate it with passion. No guarantees but if it fits your clay now you know that by simply adding silica to this it can go from matte to gloss, rough to buttery, metal marking to non metal marking. The more you can learn the more you can solve. Link to comment Share on other sites More sharing options...
bryandave Posted October 8, 2021 Author Report Share Posted October 8, 2021 hi bill thx for the reply again! u advice is so helpful to me, for me this time is quite a self learning experience, i looked after a lot of boboks and information , and try to fire it with different marterial, everytime, the result gave me suprise, although not very good everytime! i will keep on revising this glaze until i can find my perfect one! (and the texture is so good now, only things is the crackle problem) back to the receipt, now my R2O is already 0.2 how can i make it better？ attached is more photo of what is it looks like. as you can see the crackle is different on different clay ! and below is my updated receipt. see if you have any comment on that potash Feldspar 37.80 Dolomite 16.00 Kaolin 15.00 Ferro Frit 3124 7.80 Wollastonite 7.70 Talc 7.00 Silica 5.70 Calcined Kaolin 3.00 Tin Oxide 3.00 Link to comment Share on other sites More sharing options...
Bill Kielb Posted October 8, 2021 Report Share Posted October 8, 2021 Nice crackle, save that recipe! I think I looked at this base with your initial ingredients and location in Stull and entered the following to try attempting to get about a 0.2:0.8 R2O:RO and .54 - .56 alumina and keep your boron at about 0.15 for cone 6. With mostly your materials calcined kaolin - 26.79 3124 - 25.00 silica 9 -> 19. = matte -> Gloss.. dolomite - 8 talc - 12 wollastonite - 4 neph sy. - 20 Thats as much as I messed with this, I needed neph sy for the alumina but the more neph sy the more sodium which likely becomes a crazing issue. Anyway, your current recipe is so different than the earlier, I don’t think these choices apply anymore. Some real good content here about glazes …. And it’s free https://suemcleodceramics.com/understanding-cone-6-nceca-presentation-2018/ lots of things from boron to crazing, it’s definitely a good read I would recommend. Link to comment Share on other sites More sharing options...
Min Posted October 9, 2021 Report Share Posted October 9, 2021 @bryandave, are those two different claybodies? Seems the crazing is worse on one than the other. 20 hours ago, Bill Kielb said: calcined kaolin - 26.79 3124 - 25.00 silica 9 -> 19. = matte -> Gloss.. dolomite - 8 talc - 12 wollastonite - 4 neph sy. - 20 I would suggest not using all calcined kaolin if you try Bills recipe, I'ld go with around 20 kaolin and the remaining calcined (balance it to allow for the loi). I have a hunch this is going to craze also, I think there is going to be too much high expansion sodium in the formula. I like the increase in boron and silica though. Revisiting your last recipe, I think the silica is too low (for a durable glaze), the sodium and potassium too high (contributing to crazing on your clay) and the boron too low for a good melt at cone 6. I think there are a couple ways to attack this glaze if you want to put the time into tests. First off reduce the high expansion fluxes (sodium and potassium). Replace those with low expansion fluxes, more magnesium and or lithium. Lithium supplied from spodumene or lithium carb, problem with this is lithium can effect the melt so you might loose some of the matte quality of the glaze. It also needs more silica which is going to throw the silica to alumina ratio off so that would need adjusting. How much silica and alumina can be taken into a melt is going to be trial and error. It might be okay with more silica but I think the craze lines are too close together on that one glaze sample you posted for this to work. Going back to Neil's suggestion of trying a different glaze recipe, I use a version of this glaze blended with my low expansion clear to make a good semi matte that doesn't craze on my low expansion clay. If you can get Ferro Frit 3249 where you live the other version of that glaze has a bit better a melt. If you have a clear that fits your claybody I would give it a try, blend your clear with the matte base to fine tune the amount of matteness. To make it white add tin or zircopax. I haven't found a durable fully matte glaze that withstands cutlery marking, I don't know if you need this glaze for food surfaces but having a semi matte/gloss resists cutlery marking better than a matte. Link to comment Share on other sites More sharing options...
Russ Posted October 9, 2021 Report Share Posted October 9, 2021 To keep the buttery look and feel increase both dolomite and talc in your adjustments. That adjustment is up to youhow you do it in order to keep the glaze stable. Crackle is indicative of a non-stable glaze but often a great addition to your glaze palate Link to comment Share on other sites More sharing options...
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