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Amaco Ancient Copper, is on the left. Right is G3948A, our iron red (a publicly available recipe). Both of these have been fired using the C6DHSC slow cool firing schedule. As you can see the PC-56 crystallizes more, matting the surface in the process. But if cooled normally (e.g. using the PLC6DS schedule) it does fire similar to G3948A. Likewise, G3948A can be made to crystallize more if the iron oxide percentage is increased in the recipe (we use black iron, it is a little less concentrated than red but does not gel the slurry). The recipe offers excellent slurry properties when mixed as a dipping glaze. Our version uses Spodumene (which has 7% Li2O). Of course, lithium materials are very expensive these days, but that is what is needed for this effect. If you make a brushing glaze of it using our instructions only about 70g of spodumene is needed to make a 500ml jar. At current material costs, we could make 3 jars for $10 worth of powdered materials!

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This is G3948A (similar to the popular Amaco Ancient Copper product). To get this stunning result, it needs to be applied thickly. Therefore, it runs a lot. But the catcher glaze around the bottom of these mugs has stopped the flow. The catcher is a glossy black, G3914A (but Amaco Obsidian would also likely work). I have learned to put it on with the right height (about 2cm) and right thickness, and then apply wax emulsion to prevent the iron red glaze from sticking during dipping. The inside glaze, G2926B, is one I have tested and developed to fit Plainsman clay bodies as a liner.
| Glossary |
Iron Red Glaze
A type of ceramic glaze, typically fired around 2200F, where iron oxide in the cooling glass precipitates out to form a striking red crystalline mesh on the surface. |
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