Tyler Miller Posted August 9, 2014 Report Share Posted August 9, 2014 I just shut off the kiln for the night and I thought I'd share some of the reading I've been doing while the firing's been going on. A while ago I posted a little something about Achaemenid glazes. I've kept thinking about them since then, curious about figuring out a formulate for myself. I found a very interesting essay here (http://www.gustav-weiss.de/files/GW_Essay-02_The-Origins-of-Glazes.pdf) on the origin of glazes. I highly recommend giving the essay a read, it's very insightful about just how glazes came about. "Chemical analyses (Hedges 1982) from the Achaemenid, Parthian and Sassanid periods (from 700 B.C. revealed glazes with the following boundary val- ues: 6-8 % Na2O, 2.5-4 % K2O, 4-8 % CaO, 2-4 % MgO, 2-3 Fe2O3, 4-8 % Al2O3 und 65-75 % SiO2. After a phase diagram by Morey (1930), this ratio of alkali to earth alkalis and silicic acid needs a firing range of 900°-1100°C. These glazes were ap- plied to a body with 16-17 % CaO, 5-6 % MgO und 50 % SiO2, which corresponds to the lime-rich clays of the Middle East." 10% soda ash, 10% potash feldspar, 10% dolomite, 10% kaolin, and 60% silica puts you right in the ball park of that chemistry. Historically, this would likely have been soda/natron and local sand, just like Egyptian glass. Edit: It occurred to me that I should share how I arrived at that recipe. The essay talks about plant ash and sand as the origin of this type of glaze, but I'm not sure how realistic this is when trying to replicate the result. I tried every known plant ash, and I couldn't make it work. There are plants in the mediterranean and elsewhere that take up soda and potash in tremendous quantities, e.g saltwort (salsola soda), but I don't have those, and it was later found in ancient glass making that substances like natron form a better glass than ash. In fact, it wasn't until the breakdown of trade routes that ash became important in glassmaking again. Thought I'd share Link to comment Share on other sites More sharing options...
Babs Posted August 9, 2014 Report Share Posted August 9, 2014 How does that compare to Eygyptian paste? Link to comment Share on other sites More sharing options...
Marcia Selsor Posted August 9, 2014 Report Share Posted August 9, 2014 I like the explanation of the environment and the soil's development of chemical content. Very interesting. It does sound like Egyptian paste with the migration of the body chemicals helping to flux the surface. Marcia Link to comment Share on other sites More sharing options...
Tyler Miller Posted August 9, 2014 Author Report Share Posted August 9, 2014 Babs, I think Egyptian paste and the glaze I posted are very similar indeed. Modern Egyptian paste recipes I've seen are nearly identical in composition, but they seem to have more feldspar, perhaps used as a body flux. Link to comment Share on other sites More sharing options...
Bob Coyle Posted August 12, 2014 Report Share Posted August 12, 2014 WOW! Thanks for the reference Tyler. I got interested and went to Weiss's main page http://www.gustav-weiss.de This guy is amazing! I also love the great display of his glaze painting and sculptor. Spent about three hours reading his essays and looking at his art. This guy is a true ceramic philosopher not to mention a fine ceramic artist. Link to comment Share on other sites More sharing options...
Leila Posted December 14, 2019 Report Share Posted December 14, 2019 On 8/9/2014 at 7:31 PM, Tyler Miller said: I think Egyptian paste and the glaze I posted are very similar indeed. Hi, That is what I am trying to find out, but after quite a lot of reading, I did not become wiser (on this matter). I found a lot of recipes and how-to's about Egyptian paste, none about Egyptian glaze though. It is obvious : they used a glaze which produced a similar colour. This figure, for example, has not been modelled in Egyptian paste: https://www.metmuseum.org/art/collection/search/548310 nor this : https://www.louvre.fr/en/oeuvre-notices/chalice-form-lotus Has On 8/9/2014 at 7:31 PM, Tyler Miller said: I think Egyptian paste and the glaze I posted are very similar indeed. Has somebody tried this, or a similar glaze? I remember the colour of Achaemenid antiquities resembling Egyptian paste. Link to comment Share on other sites More sharing options...
Babs Posted December 15, 2019 Report Share Posted December 15, 2019 Could pm the original poster. 2014 original post Link to comment Share on other sites More sharing options...
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