braeden.ness Posted November 19, 2015 Report Share Posted November 19, 2015 I am fairly new to this group of what seems to be very helpful people and i would like to ask for some help. I live in a place that has an abundant supply of natural black clay. I have no problem with refining the clay, but I am open to helpful tips and tricks, but i am not sure how to go about testing it in the kiln to determine if it is a low-fire or high-fire clay. If any of you can shed some light on this topic i would be grateful. Link to comment Share on other sites More sharing options...
Denice Posted November 19, 2015 Report Share Posted November 19, 2015 If you would let us know what area of the U.S. or the world and what type of area that you are digging the clay from would help in answering your question. Denice Link to comment Share on other sites More sharing options...
Surubee Posted November 19, 2015 Report Share Posted November 19, 2015 Black clay that you find naturally is often black because of organic matter which will burn out when fired. The color could change to something brown or red after firing. One way you can test it is by making little cones and pinch pots which you fire first to bisque temperature, and then higher if it survives. You can also make a clay ruler to test for shrinkage and another piece to test the amount of water it absorbs after firing so you will know if it is vitrified. To protect your shelves, make sure to fire the test pieces on a piece of scrap shelf or a pad of bisqued clay with raised sides. I have seen tests of these natural clays that have totally melted at high fire temperatures, but are great at lower temperatures. If it has a low melting temperature but a nice color when fired, you may be able to use it as a base for a slip or glaze. Link to comment Share on other sites More sharing options...
braeden.ness Posted November 19, 2015 Author Report Share Posted November 19, 2015 I live in central Texas a little ways out of Austin. And thank you Surubee it sounds awesome and i am really grateful for the helpful information that this community has provided me. What really got me interested in black clay is watching videos of Japanese artists mixing black clay with other clays, simply because of its unique property of picking up small details. again thank you for all of the support. Link to comment Share on other sites More sharing options...
bciskepottery Posted November 20, 2015 Report Share Posted November 20, 2015 You can also check with the local geologist/agriculturalist who has knowledge of local clays and soils. David Hendley makes his own clay and slips from local sources; he is in Maydelle, TX. He is a very helpful person and might be able to offer you some insights. http://www.farmpots.com/ Link to comment Share on other sites More sharing options...
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