I posted earlier about making sculptural teapots out of raku clay that I hoped would be functional. I'm happy to report that one of the two sculptural teapots actually holds liquid and pours reasonably well. The other teapot developed a crack in the base, so it's strictly non-functional.
The weirdest part of this teapot experiment has been the result of the final glaze firing. I've never known a clear glaze to turn green when fired!
As usual, I bisque-fired to 06, then applied a copper carbonate wash and fired to cone 4. Next came underglazes fired to cone 6 followed by a clear matte glaze fired to cone 05. The glaze had thickened since I last used it, but I wrongly thought it would thin out in the firing. Consequently the "boat" teapot came out with a disappointingly thick glaze. However, the greenish hue that developed in the firing is the most disturbing outcome. I'm guessing the copper carbonate is the culprit, but I've followed the same steps before without this problem.
In a separate load I followed the same process but instead of firing between the underglaze coat and the topglaze, I applied them both and then fired the round "rabbit box". The box was painted in pale watered-down underglazes, then top glazed. That bright green box in the photos is what came out of the kiln!!
It has been recommended that I switch to manganese wash in place of the copper carbonate, which I will do. But I'm still curious about why this happened. The images attached show the "mountain" teapot which developed a crack in the bottom, so I didn't bother to glaze fire it....which is why it's the only thing that isn't greenish! The "boat" teapot is shown in its orginal colors after the underglaze firing but before the top glaze firing. And then it is shown as it came out of the final glaze firing with a distinctly greenish cast. The round box was originally painted in off white with pale green leaves but after firing, it came out bright green.