It took me a while to get around to sending my favorite rocks off to be analysed. I had wanted to try doing it myself at Utah State University, or at least going through our geology department. Unfortunately, the USU XRF (X-ray flourescence) machine was not working and it did not seem like a fix was coming soon. So, after a fair bit of trying, it became clear I should send them off.

A geology professor and friend recommended Washington State University’s lab. I contacted them and found them very responsive and professional to work with. I sent off three of the rocks I have been experimenting with for analysis:

DP: Devil’s Playground granite

CM: Craters of the Moon basalt (collected outside the national park)

HD: Hyrum Dam lake sediment

The results came back in 6-8 weeks, and cost $60 per sample. As a student from a research institute, I got a deal; normally they charge $120 per sample. Below is the meat of the analysis I received in an Excel spreadsheet…

This may not look very interesting to you, but to me, after having performed many “trial and error” glaze tests with these materials, it was fascinating.

I can now say, after having run some tests with the knowledge of what is in my rocks, that this information is invaluable. I did manage to hit on some nice glazes with a more haphazard, trial and error approach, but now my tests can be much more focused.

How come?

I inputed the data above into glazy, so now I have these materials in my tool kit. Let’s say I want to aim at a tenmoku and find a nice-looking recipe on glazy. I can now target that recipe, substituting my materials for some in the recipe. For my granite, I can reliably substitute out some or all the feldspar and silica in a recipe. Theoretically, if you target a recipe and match the unity molecular formula with new materials, the glaze should come out the same.

You would go through this process if a mine stopped producing a material you used. This happens all the time to potters… feldspars especially seem to go out of production with alarming regularity. I know from experience that these mathematical substitutions rarely work 100%, but they get you close… really pretty close. A few tests around the area should get you to the desired result quickly. Far, far quicker and with fewer tests than the way I was doing it before.

Why not go and collect your own materials and use them instead of relying on industry? Getting a XRF analysis and using glazy represents some upfront cost, but in the long run, you will have unique materials and ones that will never run out. Once you learn your materials, making each new glaze becomes much easier.

I am thrilled with this new method. New to me anyway, haha. I take no credit for it whatsoever. It just took me a long time to come round to the idea. Two great book to get you started in this way of testing glazes are Matt Blakely’s “Rock Glazes Unearthed” and Ian Currie’s two books detailing the “Grid Method.”

If you have any questions, don’t hesitate to reach out to me. I am always happy to talk about glazes! My email is hamish.jx@gmail.com

And here is the link to the geo lab at WSU again: https://environment.wsu.edu/facilities/geoanalytical-lab/service/sample-submittal/