HyperGlaze Tips

Stan Sulewski sent in the following story about teaching a glaze class this summer at Millersville University in Pennsylvania, and how he used HyperGlaze with his students to solve a number of problems. He DID teach the class hand glaze calculation first, but the students really appreciated having HyperGlaze to do calculations faster!

Stan writes:

We solved a number of problems efficiently using HyperGlaze. Our methodology was to create a new card for each new glaze, then call up the Glaze Limits window, and pressing the ‘Get Current Glaze’ button. Then we duplicated the original card and made changes to the original glaze, using the original glaze’s UMF in the Glaze Limits window for reference.

For example, a pink glaze that used tin oxide and rutile shivered and ran badly. It had a very high Si:Al. We made several adjustments, raising the alumina and lowering the alkali, creating a new glaze that doesn’t shiver, doesn’t run too much and has a richer color. In another, the end members for a Gloss to Matte Line Blend were created. First, the gloss was entered in HyperGlaze. It’s Si:Al was 11.7:1. We chose 4.3:1 Si:Al for the matte, adjusting clay, silica and alumina hydrate to achieve the target. The end members had the same refractory to flux ratio (RO2 +R2O3). By executing an 11-member line blend, the student developed a range of textures from gloss to matte. A third example was one of the school’s chrome-tin pink glazes that had some problems with color stability. The UMF showed a fairly high combination of amphoteric oxides (alumina and boron) that I have found to be detrimental to the color. Lowering the amphoterics by .07 in the UMF was enough to stabilize the color. The new glaze holds color even where it’s thin, like on the corners of embossments. The final example was a conversion of a cone 10 glaze to cone 6. It was accomplished by exchanging lower melting fluxes for portions of higher melting ones (e.g. Li & Na for K, Sr for Mg) and lowering the refractory to flux ratio from 3.5:1 to 3.2:1. All changes were dispatched in short order using HyperGlaze.

These are just a few of many examples that the class resolved during our five week course. HyperGlaze enabled students to generate new formulas quickly so that more tests could be done in a relatively short amount of time.

Nope, that’s not a typo. This month a short note about how the way your materials are processed can change a glaze - things like silica flour. One common aspect is the mesh size of ingredients. Generally, the finer the grind of the material the more easily and quickly it is incorporated into the glaze melt. The larger the mesh number, the finer the grind. Silica is commonly supplied in a number of different mesh sizes. The most common form of silica for glazes is 200 mesh and finer, but it’s also available in 90 mesh (or even coarser 30 mesh silica sand) and 320 mesh. 320 mesh silica is sometimes specified in glaze recipes, and may make noticeable a difference when it is or isn’t used in that particle size. Most other ceramic materials are provided in the United States in powdered form, ground to 200 mesh or finer so they can be directly added to glazes and mixed.

Occasionally, materials come a little more coarsely ground, or you may find your own natural source. In this case, you may want to ball mill the glaze before using to reduce the particle size for a smoother melt. However, too much ball milling can grind the glaze to too fine of particles, making it melt more fluidly than expected. Another side effect of too much grinding can be that the glaze shrinks more in drying on the pot, creating application problems. And grinding some materials isn’t recommended at all, as it may cause other problems such as increased leaching of soluble portions of the material in the raw glaze slip, or in the case of zirconium encapsulated inclusion stains (highfire red stains, for example) grinding may even destroy the stain.

Just a quick note for April (okay, it’s later than April, but I’m trying to get caught up with my one-post-a-month plan - foolish me…) to talk about how one can be fooled by limit formulas. Limit formulas are best used as merely advice about glazes, not rules that must be followed. There are lots of very useful glazes which fall outside of the so-called ’standard’ or ‘food-safe’ limits, and will still be perfectly good glazes and quite possibly even food safe. Food safety can best be determined by having the glazes tested by a dependable lab, if you have questions about a particular glaze. If you’re making sculptural ceramics, many of the more interesting glazes for sculptural texture and color fall outside the more industrially-based limit formulas.

One other aspect of glaze calculation that can fool you is the calculated thermal expansion. For a range of gloss glazes which don’t contain lithium or strontium, the calculated thermal expansion can often be very close to the real measured thermal expansion. For everything else, the calculated thermal expansion is at best an indicator of the likely range of thermal expansion and how it might change with a change of ingredients. For matte glazes this is because matte glazes contain crystalline materials (those little tiny crystals in the glaze are what makes the glaze matte as it cools and the crystals form), and crystalline materials have much more unpredictable thermal expansion. So take calculated thermal expansion with a bit of skepticism, but it is still quite useful when you’re trying to adjust a glaze to stop crazing, if nothing more than giving you an idea of what a change in materials might do to change thermal expansion.

Often we make new versions, new colors, slight variants, etc. of a particular glaze. While you can keep notes on this type of thing in the Comments section of HyperGlaze, it may be more useful to have a separate recipe for your ‘new’ glaze.

The easiest way to do this is to go to the original recipe in HyperGlaze, then choose Duplicate Card from the Edit menu of the Glazes window. You’ll instantly get an exact copy of the original recipe. Rename it (add ‘revised’ or some other way to know it’s a different recipe), and then add your other changes to the recipe and save.

This is an easy way to work with the recipe, adding ingredients or changing amounts to see how the estimated thermal expansion or molecular formula changes. If you’d like to have the original recipe in a window to compare it to your altered recipe, go to the original recipe, choose ‘Compare Glazes’ from the Glazes menu, and when the window opens, click the ‘Get Current Glaze’ button at the bottom of the Compare Glazes window. You’ll see the recipe in the Glazes window repeated in the Compare Glazes window. This window floats over other windows, so move it to a convenient spot on the screen, then go back to the Glazes window and find the new glaze that you’re altering. You can go anywhere in HyperGlaze and the Compare Glazes window will stay visible until you close it. Even when you open it later, it will still show the last recipe you chose to view.

You can email recipes from HyperGlaze very easily. If your friend has a copy of HyperGlaze, send the recipe as a HyperGlaze file that they can import right into HyperGlaze without having to retype it. If they don’t have a copy of HyperGlaze, you can still quickly send a recipe as email text. Here’s how to do both.

Let’s do the email text version first (also helpful for making those glaze handouts!).
Go to the recipe you want to export, and make sure you’re in the Glazes window. Choose ‘Copy Recipe as Text’ in the Edit menu, then make your choice of one of the three submenus: Recipe Only, Include Comments, Include UMF
Recipe Only just copies the basic recipe items. Include Comments gives you the full text of any comments you’ve entered along with the recipe. Include UMF copies all of the above and adds the Unity Molecular Formula to the end of the copied text.
Then just paste the recipe into your email or a word processor!

Sending a HyperGlaze formatted recipe is just as easy: Choose ‘Export as HyperGlaze file’ from the File menu of the Glazes page. You’ll be asked to save the exported Glaze file. After saving, you can attach it to an email and send it off to your HyperGlaze owner friends. If you have several recipes to share, first Mark them using Mark Card in the Glazes menu, then choose ‘Export Marked Cards as HyperGlaze file’ from the File menu. All marked recipes will be included in one HyperGlaze file that can be emailed and imported by your friends.

About cone 6 glazes: they are different than cone 10, especially the glazes that depend on iron oxide for color - they just don’t do the same kind of things at cone 6. That’s not to say that you can’t get beautiful iron colors at cone 6, but you won’t get quite the same celadons, temmokus, etc. - the classic Japanese/Chinese colorations. Additionally, if your cone 10 glaze is a glaze that requires firing in a gas reduction firing, changing the glaze to cone 6 and firing it in an electric oxidation kiln may give very different results indeed.

HyperGlaze does work well in lowering or raising glaze firing temperatures, but the problem with some cone 10 glazes is that there’s nothing in the glaze recipes that really will get them to melt well at cone 6 even if you add more. For instance feldspars don’t really melt at cone 6 well. Changing from potash spar to nepheline syenite may give you a bit of a boost in this respect, but even neph. sy. isn’t really getting very fluid at cone 6, so frits may have to be added. I often use Ferro frit 3195 for this as it seems to be the least likely (amoung the frits mentioned below) to induce crazing problems.

What you will be able to get at cone 6 is a bit broader palette of colors from stains, especially if you fire in oxidation, and with some of the more stable new stain colors, in reduction as well. There’s a glaze you might try in HyperGlaze called Clear RB that I devised as a result of a class Lana Wilson and I taught at Penland. It’s very fluid (it actually works at cone 3 quite well and isn’t so runny), but you can make a really nice cone 3-6 celadon from it using about 0.5% Victoria Green (6204) mason stain. I’ve also revised a version of this glaze to be less runny and less likely to dissolve stain colors - recipes for both of these are below. Basically, I used HyperGlaze to raise the firing temperature 2-3 cones.

Here’s my favorite hint for trying to lower the firing cone of a glaze without any calculations: adding 10% gerstley borate to almost any glaze will lower the glaze about 2 cones. 15-20% additions of GB will take a cone 10 glaze down to cone 6, but will change the glaze somewhat. Remember to add the FULL percentage of colorant in the original recipes to the batch size that includes the GB (20 percent GB really dilutes the glaze - one fifth of the original glaze is now GB, so you’d want to add an equivalent amount more of colorants).

You can also use lowfire frits in a similar way (Ferro frits 3124, 3134, 3195, 3110) to the GB. Picking a frit that has similar qualities to the original glaze may help to minimize any change to colorant results. For instance if you have an alkaline-dominated glaze (lots of sodium/potassium), adding frit 3110 might keep the alkaline quality better than GB.

You can use lithium carbonate, too, if you’re trying to lower a strontium or barium matte type glaze, but use about half to a quarter of the lithium carb compared to adding GB or a frit. So to lower a glaze two cones you might try a 2-5% addition of lithium carbonate - start with the smaller amount as lithium is a very strong flux. It may also induce pinholing. Small lithium carb additions can be useful when switching from barium (with it’s strong affect on colorants) to strontium (which is a bit more like calcium-based/middle of the road glazes), or with alkaline glazes. For instance it will help copper give the turquoise blue of barium-fluxed glazes instead of the more greenish blue-green that is typical of strontium-fluxed glazes.

Glaze Name: Clear-RB
Cone: 3, 4, 5, 6
Color: Clear
Surface: shiny or glossy
Firing: oxidation
Testing: Tested

Recipe: Pct Amount
Ferro frit 3195 70.00
EPK 8.00
Wollastonite 10.00
silica 12.00
TOTALS: 100.00

Also add these colorants and additions:
epsom salts 0.25
bentonite 2.00

Comments:
Doesn’t craze, no bubbles in glaze - very clear, has a bit of flow if thick. Should be a good, durable, food safe glaze. Good as an oxidation celadon with 0.1% copper carbonate plus 0.5% Mason 6201 Celadon Green stain - nice light bluegreen.
Works well at cone 3, too, still a nice gloss. Good reds and orange with zirconium inclusion stains at about 12% at cone 3, but will pinhole with these stains at cone 6.
If you use this with stains like Saturn Orange, add 10% zinc oxide to make it more orange (still a bit dull orange, but better).
Dark green with 4-5% copper carbonate.
Nice celadon with 0.5% Mason 6204 victoria green stain. Tested with a wide variety of stains at cone 6-15% needed for maximum color. There’s a bit too much boron in this for use with a lot of stains - the color dissolves. Try this as a possible majolica, too - adding 12% zircopax OR 7% tin oxide, along with additions of CMC to harden the glaze surface for painting).
Nice over oxide washes on texture. Notable wash colors include:
(measured by volume - teaspoons)
bluish grey black - 9 parts Manganese dioxide + 1 part cobalt carbonate
golden tan - 1 part rutile + 1 part gerstley borate
blue green - copper carbonate 3 + cobalt carbonate 1
purple red brown: crocus martix 1 + cobalt carb. 1 + gerstley borate 2
warm gold: crocus martis 1+ rutile 2+ gerstley borate 1
softer green: crocus martis 1 + copper carbonate 1
brown black: 1 copper carbonate + 1 manganese carbonate
Penland glaze class variant modified from 2004 Kate the Younger’s Clear

Unity Molecular Formula
0.001 K2O 0.396 Al2O3 3.150 SiO2
0.224 Na2O 0.781 B2O3 0.001 TiO2
0.761 CaO 0.001 Fe2O3
0.014 MgO

Look for new posts coming soon on different HyperGlaze topics like changing glazes so that they will melt at a different cone, substituting materials, and more.