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Adding a frit of unknown chemistry in a glaze recipe?

That is like adding a dog of unknown breed to this team. How predictable is that going to be? It is like that with ceramic glazes. They fire the way they do because of their chemistry. Not knowing the chemical makeup of a key ingredient robs you of the single biggest tool to explain characteristics or issues or propose adjustments, improvements or fixes.

Monday 27th January 2020

Sedimentary clays are a whos-who of the periodic table

These are the results of a detailed elemental composition analysis of a sedimentary clay. The first column of numbers is ppm (parts per million), divide them by 10,000 to get percent. The Fe here, for example, is 50,868 or 5.1%. The second column is +/- error. Notice that this test does not detect ... more

Friday 24th January 2020

Things that are too big to 3D print can be done in two pieces

This jigger mold shell has a step that provides the ideal place to split it into two pieces for printing. It is not necessary to do it in your 3D design app, 3D slicer software has the ability to do just before printing. In Simplify3D you just push the object downward on the platform (anything below ... more

Thursday 23rd January 2020

Cuerda seca is a flexible technique at any temperature

The mug is has an unglazed (bare porcelain) outside surface. The cuerda seca lines containing the glaze have a formulation to flux and melt more than what is typical in the classic technique on tiles. And this appears to be reduction-fired porcelain at high temperatures (because of the iron specks ... more

Thursday 23rd January 2020

Cutting out the background on a photo

White backgrounds are used for presentation on ecommerce websites (contextual backgrounds when showing a product in use). Even if you can photograph to pure white at the edges of a photo, it will transition to grey around the object and pieces will almost always have some fuzzy edges. While there ... more

Monday 20th January 2020

Melt fluidity comparison - 1650F

Fired at 350F/hr to 1650F and held for 15 minutes. FZ16 has turned crystal clear and spread out across the runway (has low surface tension). Frit 3110 has so much surface tension that the flow can be lifted off the tester. Since 1600F Gerstley Borate has gone from unmelted to passing all the rest!

Wednesday 1st January 2020

The myth of aging clay

Do you really need to age clay when you make your own? No. In ancient Japan they did not have power blenders and propeller mixers, we do. To illustrate: I just sieved out the +80 mesh and +200 mesh particles from this raw clay (from one of our stockpiles) and then propeller-mixed it as a slurry. ... more

Wednesday 18th December 2019

Aged commercial clay really needs to be wedged before use

This is a cut through an eight-month-old slug of pugged clay. The cut was done near the surface. The patchy coloration is a by-product of the aging process. If a slice of this was fired in a kiln, an even and homogeneous white surface would emerge, with no hint of what you see here. A few moments of wedging will mix the matrix and ready it for wheel throwing or hand forming.

Wednesday 18th December 2019

Hand-tooling a mug model vs. 3D-printing a mold to cast it

I am creating molds for a 2019 casting-jiggering project to reproduce heavy stoneware mugs manufactured here 50 years ago. I have a profile drawing I want to match (upper left). The solid plaster model on the left was my first attempt at manual tooling. The metal template was time-consuming to ... more

Friday 13th December 2019

Cone 10R mugs made with new casting-jiggering process

Very exciting! The easiest batch of mugs I have ever made, no wheel throwing or trimming. These are made from two casting recipes I am working on to match the fired appearance and glaze compatibility of Plainsman H550 and H440 (buff and iron red burning bodies). This is how many you have to make to learn some of the finer points of the process.

Friday 13th December 2019

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Chemistry plus physics. The on-line successor to desktop Insight. Get an account for as little as $15. It does so much more.

Conquer the Glaze Dragon With Digitalfire Reference info and software

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Interactive glaze chemistry calculations (legacy, no longer supported)

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