This Website has glaze calculation software that you can use free online.  Thank you, Zoophagous, for mentioning it on your blog.

Here is the link to visit the website -----> 

If you have never worked with glaze calculation software, this is a great place to try it out.  It has wizards to help you adjust your glazes to eliminate defects that you won't find in the Glazemaster or Insight software, as well as a straightforward user interface.  I just tested it for a few minutes, and will look into it more, but for now, I just wanted to get the word out to our members, and let you all try it for yourselves.  Please post your thoughts on here on this discussion.  It looks like it could be a very useful tool for a lot of people who want to formulate or improve glaze recipes.

Norm Stuart updated the information on glaze simulator with the following image from the site:

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Hey George,


I really like this site. No idea who put it together. I have been using it to take some cone 10 glazes and tweak them to cone 6. Very useful. 


I expect to start to use it to convert from formula to recipe soon (a soon as I pick up a copy of Nigel Wood's Chinese Glazes).

Maybe I'm doing something wrong but I am getting weird results. I have entered numerous recipes that I know are good cone 6 recipes and it tells me they mature anywhere from 04 to above 10. Its also telling me that most glazes are going to be matt finish and Iknow most are glossy. ?????
Lenny, There might be a simulation program out there in high end scientific ceramics circles that could with a high degree of certainty determine what a glaze recipe would be like when fired, but it really doesn't work for real world potters using the software available today.  Your recipes were probably entered correctly, but the combinations of glazing variables work against having highly accurate predictions come out of any software. I would say the usefulness of this site is to give you some hints of standard ways to go to change a recipe to correct defects.  The site is also good for converting your recipe from weight percentages to flux unity and Seger percentages from where you can check against limit formulas and make reasonable choices in doing adjustments.
Thanks  for the information George, I'm finding it more and more difficult to get my glaze test to come out right with the ever changing chemistry of glaze chemicals, this site should help.  Denice (Wichita, KS)

Hi just saw your thread. Thanks for posting information about

Just want to respond to the post regarding firing and ratio (shine vs matt) property predictions. First ratio is simply a value derived from the ratio of silica to alumina in a recipe. If the pgm predicts a matt surface for a glaze that is gloss it could turn out that you are firing a glaze beyond it's ideal range. Every pgm will use this formula to calc ratio so there is not much you can do. (Personally I think matt finishes have much more to do with ample amounts of things like calcium, barium, magnesium etc and a slow enough cooling phase to promote micro crystals. And to that end does include a msg about slow cooling and crystallization in the Ratio rollover. But ratio is a traditional formula you will find in any glaze chemistry text)

As far as melting prediction the pgm uses limit formulas primarily to estimate melting ranges. (please note the word -ranges) Just like ratio it is basically impossible for any pgm to calculate melting temperatures for a glaze simply because the recipe is only one variable out of many that will determine how the glaze melts. For example, a firing ramp could be adjusted longer by one hour and your glaze could turn out very different since you have adjusted the heat + time (work) input variable. The atmosphere in the kiln can be a huge variable esp in reduction kilns. Thickness of glaze, hardness of bisque etc will all add to variability of glaze results.

However most of the discrepancy between calculated results and empirical results comes about because most glazes melt over considerable temperatures.( I have a copper red that will work from cone 5 to cone 9)

Here's an example of what i mean. You fire a glaze to cone 7 and it turns out consistently glossy and functionally balanced (doesn't craze, shiver, crawl or run off the pot and can withstand thermal shock tests). Chances are you could fire that same glaze at cone 4 or 5 for an extra half hour and get a fully melted glaze but with a little less gloss. You also might fire it at cone 9 or 10 and still have a workable glaze but find it even more glossy.

The problem with prediction here is that there are a lot of glaze possibilities that 'work' over a large melting range i.e. it melts into something more or less functional. However other properties like ratio, surface tension, viscosity will change. At cone 4 the glaze may better approximate the ratio formula of silica to alumina while at cone 6 or 7 it will look much more glossy. 

The only way to determine if the pgm is completely off base is to test a line blend of your glaze at different temperatures. Problem here however is to adjust melting temperature of most glazes you adjust the level of clay (because clay contains the most amount of alumina - unless you're using calcinated alumina etc). However, once you adjust your clay content to alter the melting temperature you affect things like ratio, and viscosity etc. 

The level of sophistication in the  prediction software in is not really the issue. The issue is going from theoretical calculations constituting a limited number of variables to empirical testing that involves a much larger number of variables. That's why testing is so important and why the pgm cautions users to use the results as indicative of direction rather than giving a definitive result. 

There are other issues regarding melting temperature when transitioning from low melt ranges to higher melt ranges. Typically glazes melt because of flux alumina silicate interactions. However below a certain level no amount of flux will cause a glaze to melt (with the exception of a few frits). That's where boron comes in. Boron can act like both a flux and a glassformer depending on a number of factors including temperature. So will use boron information to help predict low temperature glaze melting ranges. 

Thanks again for the feedback and I will take these comments seriously and try to make improvements.


thanks for the info! very useful!
Several new additions to The most important is that you can store your recipes and materials preferences client side. This is possible because of new standards agreed upon by browser makers and it means only the newer browsers are capable. Many people have asked for some way to use the program without having to reenter recipes and material lists. Such a feature typically requires using a server based database and that requires users to register, have a password and so on....something to avoided in my opinion. What's cool about this new system is when you store recipes etc the data is kept in the browser that you're using - kinda like a cookie - but under your control.
This addition has been a long time coming.

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