Help with Glazy, recipes, charts

[Michael D]

Hi. I'm pretty much a beginner with Glazy. 

When I enter a recipe for a very matte white  into the Glazy recipe maker, it shows on the UMF chart and the Stull chart that it should be high gloss.  I know it is matte because "matte" was the recipe of the original recipe and because  it has made very matte glazes from my kiln.  I wanted to experiment with entering into the calculator more frit, or more glass to make the glaze less matte and more semi-matte, but this is throwing me off.  

Could it be that this C-6 is really just an underfired gloss?  That maybe I just need to add a little more frit to make it a little more satin?

Thanks for any advice! 

[Bill Kielb]

2 hours ago, Michael D said:

Hi. I'm pretty much a beginner with Glazy. 

When I enter a recipe for a very matte white  into the Glazy recipe maker, it shows on the UMF chart and the Stull chart that it should be high gloss.  I know it is matte because "matte" was the recipe of the original recipe and because  it has made very matte glazes from my kiln.  I wanted to experiment with entering into the calculator more frit, or more glass to make the glaze less matte and more semi-matte, but this is throwing me off.  

Could it be that this C-6 is really just an underfired gloss?  That maybe I just need to add a little more frit to make it a little more satin?

Thanks for any advice! 

7:1 Si:Al  in Stull under UMF Says this glaze fired to its proper cone would be a gloss.  It’s possible to underfire glazes and they will appear matte. Will this be durable? No one knows, probably not. You have entered the mason stains and rutile as an ingredient and not a colorant, interesting have not been in the site for a while but that explains the 113% total. Interesting in that your only flux is  whiting, for durability generally  an R2O:RO of 0.3:0.7 would be most durable with an acceptable durable range down to 0.2:0.8. Fluxes are important to make things melt to form a strong glass. The flux ratio in general indicates early melters to late melters and both are generally needed to make a durable glaze.

There are many ways to evaluate glaze so not everyone is a fan of RT Stull ..... but looking at your recipe, it is odd in that it’s mostly silica and only has a single flux. That it fires matte but Stull says it should fire gloss (Without slow cooling)  is an indication it does not fully melt at the temperature it’s being fired to.

where is the Fritt in the original recipe and which Fritt?

Here is a beginners type intro to some of this

 

[Callie Beller Diesel]

What is your firing cycle, and what do the witness cones tell you about how complete it is? Is it reaching a true cone six, or is it only getting to 5? Any soak holds? How fast is it going?

[Michael D]

Thanks Callie and Bille.

That was an enlightening video, Bill. Thanks!

I do a drop and soak, Cone 6 and the witness cone says that it fired nearly a full C6; (I have other C6 recipes in there that were gloss, and they turned out great.) Maybe it is a problem of slow cooling (many shelves with tiles). But again, the other tiles came out great. 

After watching this video, I think it's clear that I need more flux. or frit. 

Here is another question: I have no idea when looking at the Stull chart, and R2O, what the cone for the recipe should be. This helpful video says that Boron should be .18 for a Cone6 firing. But I don't see on Glazy where to read that level. And if that is the best way to assess what Cone the glaze is made for.  Do you know a way to look at the date supplied on Glazy and assess the proper Cone?

thanks!

Michael

 

[Bill Kielb]

45 minutes ago, Michael D said:

Thanks Callie and Bille.

That was an enlightening video, Bill. Thanks!

I do a drop and soak, Cone 6 and the witness cone says that it fired nearly a full C6; (I have other C6 recipes in there that were gloss, and they turned out great.) Maybe it is a problem of slow cooling (many shelves with tiles). But again, the other tiles came out great. 

After watching this video, I think it's clear that I need more flux. or frit. 

Here is another question: I have no idea when looking at the Stull chart, and R2O, what the cone for the recipe should be. This helpful video says that Boron should be .18 for a Cone6 firing. But I don't see on Glazy where to read that level. And if that is the best way to assess what Cone the glaze is made for.  Do you know a way to look at the date supplied on Glazy and assess the proper Cone?

thanks!

Michael

 

Sorry old very generic video. The earth is basically cone ten, that’s where the geology basically melts and as a result cone ten is a real thing. Cone six is an adaptation,  the easiest way to melt Cone ten stuff  is to add boron to bring cone ten down to cone 6. Katz did research and the boron relationship ends up pretty linear with respect to predictability. 0.18 is actually a minor mistake As the graph I was looking at had shifted slightly and showed .18  in the video but +/- 10% of 0.15 is generally fine for cone six.  So that is the easy way to make stuff that starts as cone ten melt at cone 6. There are other ways, some are:

•  Less silica and alumina, but the amount of natural silica and alumina almost relegates this to neph sy. After all we need to use what is available geologic chemistry.
• More flux, but there are real limits And durability issues  to making a good glass simply using more flux is not the most durable.
• Special properties of flux in certain ranges of operation. Look up zinc and Bristol glazes.

Glazes melt by composition so they will appear (more or less) in one area of the chart. Stull does not predict where it will melt, just the texture of the composition fully fired. As simple as this sounds it’s very useful in diagnosing a glaze. The recipe you have is not great IMO and very likely not fully melted. Is it durable? No idea, I would say likely not.  The question always comes up as well, it works and the answer is almost always the same, why not just create a true matte recipe that works and is fully melted and therefore we have a degree of confidence that it is durable.

As I said, lots of ideas in glazes, not everyone is a Fan of Stull.  Finally different Frits contain different amounts of raw materials for very different uses. If one subscribes to glazes are made of  basic raw materials then which Fritt used will have Very different  effects on the composition.

In short though, I am not aware of anything that allows one to look at a recipe and tell which cone it will melt at. Usually we make and test. Fire up and fire down with our tests to know a glaze melts well between cone 5 and cone 7 for instance. If one has no bases to conclude that a glaze should be matte or gloss then we have no insight into whether something is simply underfired. Stull, does give us this insight.

[Min]

Unpacking your recipe and comparing it to a tried and true semi matte cone 6 glaze that has a lot of calcium in it as yours does...

First off, have a look at the MC6G  High Calcium Matte Base 1 from Glazy. 

 

 

Comparing your recipe to this one, you can see that according to the chart they both should come out as a gloss. MC6G one can be either a gloss or a semi matte, depending on the speed in which the kiln cools. Now look at the amount of silica and alumina in the glazes, yours is relying on calcium alone to flux a glaze that is very high in alumina (stiffens a glaze) and fairly high in silica. Silica will gloss up a glaze but only if there is sufficient fluxes to melt it. Oversupply silica and don't increase the fluxes and you'll get a matte. At cone 6 unless you use zinc as a flux it's difficult to get a good melt without boron. 

It's actually easier to see the chemistry when the two recipes are side by side. I entered them into Insight below.

Your recipe is the one on the left on the right is From Mastering Cones 6 Glazes , High Calcium Matte Base 1. 

Calcium is supplied by wollastonite in MC6G recipe (as is some of the silica). CaO is 1 versus 0.91  this is telling us both are high calcium glazes. Now compare the boron; 0 versus 0.20  Next look at the secondary fluxes, there is a small amount of sodium and potassium in the MC6G recipe, 0 in yours. Onto the alumina and silica, see the differences? As we know the MC6G recipe melts well at cone 6 we can then look back at your recipe and see where the could be changes. 

You can see the silica to alumina ratio is about the same so you would expect the melt to be about the same IF you only go by this set of figures. That's the problem with the Stull chart; it doesn't tell you at what cone a glaze will melt at and doesn't take into consideration slow cooling the glaze. 

To answer your question re how to tell at what cone a glaze will melt at, have a look at a limits chart for the cone range you are firing at. There is a lot of wiggle room in the figures in a Limit Chart but it will get you in the ballpark as to what range a glaze will melt at. 

[Bill Kielb]

13 minutes ago, Min said:

Unpacking your recipe and comparing it to a tried and true semi matte cone 6 glaze that has a lot of calcium in it as yours does...

First off, have a look at the MC6G  High Calcium Matte Base 1 from Glazy. 

Comparing your recipe to this one, you can see that according to the chart they both should come out as a gloss. MC6G one can be either a gloss or a semi matte, depending on the speed in which the kiln cools. Now look at the amount of silica and alumina in the glazes, yours is relying on calcium alone to flux a glaze that is very high in alumina (stiffens a glaze) and fairly high in silica. Silica will gloss up a glaze but only if there is sufficient fluxes to melt it. Oversupply silica and don't increase the fluxes and you'll get a matte. At cone 6 unless you use zinc as a flux it's difficult to get a good melt without boron. 

It's actually easier to see the chemistry when the two recipes are side by side. I entered them into Insight below.

Your recipe is the one on the left on the right is From Mastering Cones 6 Glazes , High Calcium Matte Base 1. 

Calcium is supplied by wollastonite in MC6G recipe (as is some of the silica). CaO is 1 versus 0.91  this is telling us both are high calcium glazes. Now compare the boron; 0 versus 0.20  Next look at the secondary fluxes, there is a small amount of sodium and potassium in the MC6G recipe, 0 in yours. Onto the alumina and silica, see the differences? As we know the MC6G recipe melts well at cone 6 we can then look back at your recipe and see where the could be changes. 

You can see the silica to alumina ratio is about the same so you would expect the melt to be about the same IF you only go by this set of figures. That's the problem with the Stull chart; it doesn't tell you at what cone a glaze will melt at and doesn't take into consideration slow cooling the glaze. 

To answer your question re how to tell at what cone a glaze will melt at, have a look at a limits chart for the cone range you are firing at. There is a lot of wiggle room in the figures in a Limit Chart but it will get you in the ballpark as to what range a glaze will melt at. 

@Michael D
Just to add, all good points above but slow cooling is a preference thing. Just like nothing Really tells us when something will melt nothing  tells us how much or If indeed slow cooling will improve a matte and by how much. Probably the best indicator of matte or gloss for compositional firing is the Si:Al ratio then try slow cooling to hopefully matte it out to taste. These are tested and acquired knowledge things so hard stuff actually.  It takes time, and folks have their tried and true methods many of which are great.......... and testing and discovery of a unique repeatable  result is often highly rewarding.

[Dick White]

Ok, late to the party as usual. Let's take this one from the top - a  base recipe of 41 silica,  35 kaolin, and 24 whiting yields a UMF Si:Al of ~7.1, and molar levels of 3.99 and .57 respectively for Si and Al, and  0 for Boron. Looking at conventional limits, durable glossy glazes usually have an Si:Al ratio near 7 no matter the cone. But the molar levels are a good indicator of the likely cone for proper maturation. A cone 10 glaze generally has Si between 2.5 and 5.5 and Al between .35 and .75, with B at or near zero. Cone 6 glazes generally tend to have Si between 2.0 and 4.5,  Al between .25 and .5, and B between .18 and .4.  Low fire glazes tend to have yet lower Si (1.5 to 3.5) and Al ( .15 to .4) and much higher B (>.75). So your glaze fits very nicely in the conventional limits of a glossy cone 10 glaze, and is exactly where it should be on the Stull chart. And yes, as you already stated in your original question, glossy cone 10 glazes fired to only cone 6 will be underfired matte. The other consideration, already mentioned by others, is the singular flux of Ca from the whiting. Durable glazes tend to have R2O/RO at ~3:7 +/- . You can tweak it around by adding some gerstley borate or a frit - but the word frit covers a lot of territory, i.e., which frit? Or just go with one of the suggested semi-matte glazes.

[Min]

Should probably add a couple limit / target charts to this thread. Like the Stull chart they are another tool in the tool box, they are not absolutes.

 

[Michael D]

I'm blown away by your generosity of sharing knowledge and time. Thanks to all! 

I feel like I just too a crash course in glaze chemistry, etc. I see now that the original recipe may look cook, but it is clearly an underfired gloss that may not be stable. I've am seeing now how vital it is to have an understanding of the various tools: stull, R2O ratio, glass to alumina ratio, cooling rate.... And after that it is really about testing and verifying in my particular kiln, with my particular firing schedule. 

I'm still trying to figure out the R2O/RO ratio as that seems really tricky and contingent on various things. And I am thinking that this measure has a lot to do with durability, say in a washing machine, and may have less meaning on tile, or art. 

Thanks again. I have lots of ideas to run a few more tests. 

 

Md

[Hulk]

Bill had mentioned Sue McLeod's discussion on R20/R0 ratio (try searching Sue McLeod R20 R0)on another thread - interesting read.

[Michael D]

Hello all:  as I examine the specs on glazy, trying to make sure I have enough boron for a proper melt (trying to get at least .15, it’s not clear what these numbers mean (circled in pics). It looks like I am fine with R2O. But it’s the boron numbers that confuse me. How should I see/interpret these numbers?

mike
 

[Min]

In the first screenshot the "total" and "adjusted total" are different because the adjusted total takes into account the LOI (loss on ignition) of the materials.

In the second screenshot the stabilizers you circled first are showing the ratios in a UMF (unity molecular formula), fluxes will always equal 1 therefore the other numbers, ie in the stabilizer and glass former columns will be in relation to 1.

Third circled area is showing the relationship between the 2 flux groups. R2O versus RO. When looking at this ratio the total will always be 1. In your example you have 0.21 from the first  column  and 0.79 from the second column. "R" stands for the symbol for any element that fits the situation of the chemical structure. Example would be alumina which is Al2O3 so it would go under the R2O3 column. Speaking of alumina, this recipe is quite high in it, might need to up the boron to get it all into the melt.

[Michael D]

Thanks Min!
I read somewhere that the B2O3 (or boron) should be at least .14 for Cone 6.  But you say that I may have too much alumina in the recipe for this. Is Silica easier to melt than the alumina? Is that why you suggest I get more flux (or boron) in the recipe? 

[Min]

Without making things more complicated than they need to be at this point, a few things to look at...

Have a look at the alumina and silica amounts in your recipe, from the Glazy analysis you have alumina at 0.55 and silica at 2.75  Now scroll up to the limits charts I posted in a post above. Lets just use the Hesselberth and Roy one for now, in the far right column you can see "Rge" which stands for range. Range for a cone 6 well balanced glaze has alumina in the 0.25 - 0.50 range. For silica it's 2.5 - 4.0  Now have a look at your alumina and silica amounts again. See how the alumina is a bit over the upper end and silica is on the low side of midway between the high and low range. Might melt okay as it is but if not boron is a good material to add to help dissolve alumina. Too much though and it will turn an otherwise matte glaze glossy, even with a low silica:alumina ratio.

One more thing, you can see how there is a high amount of calcium in this glaze, (0.75). One of the ways to get a matte glaze is to slow cool a glaze that is high in calcium. As the glaze is cooling the excess calcium precipitates to the surface of the glaze and forms micro-crystals that refract light causing mattness. So if you have a glaze like this one that is matte from the silica:alumina ratio and combine that with one that could be matte from slow cooling you have 2 matting mechanisms. 

1 - When you enter a recipe into a formula re-total it to 100 without the colourants or opacifiers. 

2 - When you enter a recipe be as specific as possible as to the materials being used. For example when you enter kaolin you will be getting a "theoretical" analysis unless you enter the specific type. So if you are going to be using Edgar Plastic Kaolin (EPK) then enter that to get more accurate chem. Same thing for the soda feldspar in your recipe. 

3 - After getting the base recipe sorted out and re-totalled to 100 then add colourants and opacifiers.

[Bill Kielb]

6 hours ago, Michael D said:

Hello all:  as I examine the specs on glazy, trying to make sure I have enough boron for a proper melt (trying to get at least .15, it’s not clear what these numbers mean (circled in pics). It looks like I am fine with R2O. But it’s the boron numbers that confuse me. How should I see/interpret these numbers?

Not to add confusion but maybe looking at your recipe and simple Stull analysis, the si:al ratio of 5.07:1 should fire as matte fully melted, runny matte overfired. The R2O:RO is in a known durable range so that is good and boron of 0.15 +- 10% should be fine for cone six melt. So specifically your boron numbers are in a know decent range for this to melt at cone 6. Specifying the type of feldspar and the specific clay you use is important as this will affect the analysis of this recipe..  So change the feldspar to maybe Custer ( common) and the kaolin to EPK (also common) And remove the rutile (colorant) from the recipe As a component. Then look at your numbers.

Limits are fine but we routinely exceed 0.54 AL especially to remove crazing from matte  glazes at cone 6. So limits are great but there is significant overlap between cone ten and cone six in the limits they are a decent guide ......... so all these things are simply guidelines. Proficiency with exceptions comes after a great deal of personal research and testing. There is no one master method that guarantees a specific number or outcome. Fire and test.

[poppyandlily]

Hi Bill,

Can you tell me the source of this video? I’m curious about the glaze group he speaks of.

 

thanks!

[Callie Beller Diesel]

@poppyandlily It’s @Bill Kielb’s video.

[Bill Kielb]

5 hours ago, poppyandlily said:

Hi Bill,

Can you tell me the source of this video? I’m curious about the glaze group he speaks of.

 

thanks!

@poppyandlily
I do not know the source of the recipe actually other than something pulled from Glazy last year. At least I don’t recognize this by composition or colorant as something we have used.  You could try and DM @Michael Dsee if he remembers. We have an old video (not the greatest) that does some intro Stull stuff, but it was centered around real basic Stull and the free Katz spreadsheet which we got his permission to modify and redistribute. The mods were  a bit for ease of use,  color research, etc….. of the original sheet.