GestaltArtworks

Bill, is the orange peel texture what you are calling "refractory"? I've had this happen with Speedball royal blue on a piece with multiple other colors inside/out and only the blues were affected. Seems like you're saying that painting on washed out has better results, yes?

I don't unload the bisque (I fire at a community centre so the technicians load/unload) but do rinse after wet sanding and after that it's glove only handling until after they are glazed. I've had scrubbing damage the underglaze in the past so i only use a sponge now, but wet sand in one sink basin & rinse in the second basin.

Do you mean the interaction of oils/sweat from bare hands touching before glaze is applied? I always wear gloves when handling bisqueware - after wet sanding - to avoid contaminating the surface.

As this issue is mostly on rims, I think it might be a moisture unevenness problem. Thanks for bringing this up. I'll watch the rims!

Speedball yellow, orange, amethyst and carmine have been grainy for me. Spectrum I love for the smoothness! I've done what you've suggested with test tiles; all mine have 1, 2 and 3 coats of u.g., with my chosen gloss and matte glazes, so I know which colors need more or fewer layers depending on glaze plan. I apply at the consistency of heavy cream, and am very careful with drying between layers and not applying too thickly. I feel like it's maybe not a 'too thick' issue since most of this 10 cu. ft kiln load wasn't affected, but absolutely I could be wrong so will watch this more closely in the future. Thanks for taking the time to give me feedback!

This never occurred to me before.... What are the best conditions to ensure underglaze attaches? And which colours do you add frit to?

Yes bisque then separate glaze firing. I did have to do a bit of touch up of the underglaze on one spot along the rim before glazing, so perhaps this is the answer... underglaze not well adhered! What are the conditions for best attachment/adherence? I'm guessing NOT bone dry as Babs alludes to? I spritz my pieces to maintain some body moisture throughout painting and carving, so painting for me is never on bone dry...

Actually I forgot that on this particular piece it is Spectrum black; all the other colors are Speedball though, and still a couple colors like I mentioned. Application is with small brushes for each painted shape. I've had this situation happen that you mention - especially around lips - and am diligent about making sure there are no blobs like this, the chances are they will break/flake off.

Some colors are grainy and need Darvan periodically to apply smoothly. Yes I'm diligent about applying only on dry previous coats

It's happening to a few different colors, mostly black and teal in this last kiln full. I keep my underglazes thinned with Darvan 7 & water to the same consistency, and typically apply 3 coats at the hard leatherhard stage with brushes, before sgraffito carving. The puzzling thing is, it's happening randomly yet - like on this bowl - it's just in some places around the rim only, not the whole rim, not inside, not outside (underglaze/glaze is everywhere except the foot). On pots that I've left underglaze decoration unglazed, this has never happened, so I had guessed that it had more to do with the glaze/underglaze combo, as this glaze/clay fit is perfect and I've not seen any defects otherwise. Also I wondered if it might have been too close to the kiln element, but the clay technician who fires for me didn't think so, and didn't have a clear idea of what might be causing this.

Here's a pic!

First time poster here.... have been experiencing some glaze/underglaze defects and wonder if anyone has any ideas as to the reason why... I'm using speedball underglazes and Georgie's No More Tears clear over their Trillum porcelain. The glaze crawling pulls the underglaze with it, exposing the clay body. It has happened with a few colors and more commonly on the edges/lips of plates and bowls, but closed forms also have been affected. The effect is like an archipelago of multiple small spots, a few millimetres (~1/8") diameter, usually. Has anyone else had this issue?