|Monthly Tech-Tip |
John Porter was a prolific glaze tester and developer, both in reduction and oxidation firing. We have finished taking and cataloging pictures of a treasure trove of glaze samples of his testing from the 1970s to the 1990s. Among them are also samples done by Luke Lindoe, he focussed mostly on reduction. Every one of the many hundreds of specimens was code numbered and we already know the recipes of some. We are confident that other cataloguing work will uncover more of his notes and provide clues and information to derive the recipes on many of the samples. The ultimate goal is to make all the pictures and documentation available on line for students and potters.
He was the founder of Plainsman Clays. My dad had just built the Plainsman Clays factory for him and I began working there in 1972. He was a well-known artist potter and sculptor at the time, having come out of the pottery production industry in the area. He got me started along the fascinating road of understanding the physics of clays. He was a true "plains man", interested in the geology of the plains (notice the skulls, these inspired the Plainsman logo). He got me started doing physical testing of raw clays (that he was finding everywhere). I was blown away by the fact that I could assess a completely new material and judge its suitability for many types of ceramic products and processes by doing the simple physical tests he showed me. It got started writing software to log the data for that back in the 1980s, that eventually led to digitalfire.com and Insight-live.com.
Luke Lindoe prospected Montana and Idaho for clays during the 1970s. He found an amazing variety of fireclays, earthenwares and stonewares. Every color, texture, plasticity. For each he made test bars to fire at different temperatures. Our M2 and Troy clays originated from this work. We just found these bars, but do not have Luke's shrinkage and porosity data, so are measuring them now. He code-numbered each and stamped them with four-inch marks. So we can derive the total fired shrinkages and measure the porosities. We can tell a lot about the plasticity of each by the nature of the cut lines. The texture also is obvious. Now we just need to start searching Luke's map archives to find out where all of these are.
In a ceramics lab, studio or classroom specimens of hundreds of glazes and bodies may be present. A code numbering system that links these to written or computer records is essential.