This is G2890C, a cone 6 iron red glaze. It was so gelled that it was unusable! First I measured specific gravity (with difficulty): 1.48. That's too high, so I added water to reduce it to 1.44. Then I dripped in Darvan 811 (it is recommended for iron-containing slurries). I added it until adding more did not thin it further (more was needed than for deflocculating the average non-iron-containing slurry). But it was still gelled. That means 1.44 is not a realistic specific gravity for this recipe. So I added water to take the SG down to 1.42. Now it is so much better because it does not go on too thickly when pieces are dipped.
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.