Pam S Posted October 24, 2012 Report Share Posted October 24, 2012 In the newly expanded Electric Kiln Firing freebie, does anyone know the type of clay Jayne Shatz used to get the Ketchup Red to actually come out KETCHUP Red? I've tried it on several test pieces using Buncomb White and Mary's porcelin and it always comes out a very flat and ugly rust color. I've tried it at cones 5, 6 and 7 (electric). It is lovely when used under the Glossy Black (thin), very, very nice hairfoot. Link to comment Share on other sites More sharing options...
Kohaku Posted October 24, 2012 Report Share Posted October 24, 2012 In the newly expanded Electric Kiln Firing freebie, does anyone know the type of clay Jayne Shatz used to get the Ketchup Red to actually come out KETCHUP Red? I've tried it on several test pieces using Buncomb White and Mary's porcelin and it always comes out a very flat and ugly rust color. I've tried it at cones 5, 6 and 7 (electric). It is lovely when used under the Glossy Black (thin), very, very nice hairfoot. Hi Pam... I use this glaze... and the one thing I've found is that it has to go on THICK. Twice the specific gravity of any other glaze I work with- often with multiple dips. If you under-apply, it can yield a nasty off-matte black. The clay body doesn't seem to matter that much, in my experience. I've used it over Helmer (a pseudo-porcelin) and Klamath buff from SPS. Same result in both cases. Link to comment Share on other sites More sharing options...
neilestrick Posted October 24, 2012 Report Share Posted October 24, 2012 Can you post the recipe? I don't have the booklet. Link to comment Share on other sites More sharing options...
Pam S Posted October 24, 2012 Author Report Share Posted October 24, 2012 Can you post the recipe? I don't have the booklet. Ketchup Red Cone 6 oxidation Gerstley Borate . 31 % Talc . 14 Custer Feldspar . 20 EPK (Edgar Plastic Kaolin). 5 Silica (Flint). 30 100 % Add: Spanish Red Iron Oxide . 15 % Link to comment Share on other sites More sharing options...
neilestrick Posted October 24, 2012 Report Share Posted October 24, 2012 That's a very strange recipe. The silica to alumina ratio is 17:1, which is crazy out of whack. Most of these iron reds have a bit of phosphorous in them, but this one doesn't. I think it's depending on a ton of iron in a very glassy glaze to go red. In the normal cone 6 iron reds, they often start to brown out a little on white bodies and porcelain. Sometimes slowing down the cooling helps a lot, and putting it on thick also helps. Link to comment Share on other sites More sharing options...
Kohaku Posted October 24, 2012 Report Share Posted October 24, 2012 Pam- here's a photo of a piece with this glaze on the base. I'm curious as to whether this is anything close to what you're looking for, or whether this still falls into the 'rusty' bin. Link to comment Share on other sites More sharing options...
Pam S Posted October 24, 2012 Author Report Share Posted October 24, 2012 Pam- here's a photo of a piece with this glaze on the base. I'm curious as to whether this is anything close to what you're looking for, or whether this still falls into the 'rusty' bin. You're getting much more red than I am, though not as red as the photos of Jane's work. Your piece is beautiful! What are you ding to get that iridescence? Link to comment Share on other sites More sharing options...
Kohaku Posted October 24, 2012 Report Share Posted October 24, 2012 Pam- here's a photo of a piece with this glaze on the base. I'm curious as to whether this is anything close to what you're looking for, or whether this still falls into the 'rusty' bin. You're getting much more red than I am, though not as red as the photos of Jane's work. Your piece is beautiful! What are you ding to get that iridescence? Yeah- I've seen photos where this glaze was more dramatic... but this is the best I've been able to do in a cone 6 oxidation environment. Thanks for the kind words. Do you mean the upper vessel? It's raku-fired, with a copper-based glaze, light reduction... Link to comment Share on other sites More sharing options...
Pam S Posted October 24, 2012 Author Report Share Posted October 24, 2012 You're getting much more red than I am, though not as red as the photos of Jane's work. Your piece is beautiful! What are you ding to get that iridescence? Yeah- I've seen photos where this glaze was more dramatic... but this is the best I've been able to do in a cone 6 oxidation environment. Thanks for the kind words. Do you mean the upper vessel? It's raku-fired, with a copper-based glaze, light reduction... Yes, the upper portion. It is drop dead beautiful! I had a feeling it was a raku fire. Thanks for your input. I'll try the red thicker on a test piece next firing. Link to comment Share on other sites More sharing options...
KatzPots Posted October 25, 2012 Report Share Posted October 25, 2012 Jayne mentioned in the article that she developed her own clay bodies and she included the formulas for those in the Recipe section. The red glazed goblet is stoneware, according to the article. She also mentioned that it is a "red saturated glaze" so Neil may be correct in the amount of iron having to do with the coloration. Link to comment Share on other sites More sharing options...
bciskepottery Posted October 25, 2012 Report Share Posted October 25, 2012 Iron reds tend to like a hot firing . . . try a hold at peak temperature; and they like a slow cool . . . try a hold at 1500F or so -- promotes crystal growth. Here are some pointers . . . http://www.johnpost.us/Pottery%20Links/Glaze%20Recipes/cone-six-firing-schedules-and-troubleshooting.html#troubleshooting Link to comment Share on other sites More sharing options...
Dinah Posted October 27, 2012 Report Share Posted October 27, 2012 I hold those RIO/Crocus Martis rich glazes at 840d Centigrade for at least an hour on the down fire. John Post's comments will get you closer. Check out members gallery for image. Link to comment Share on other sites More sharing options...
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