I’ve ran into an “issue” whenever I use dipping clear glaze only on the inside of cinco blanco pieces. It seems like the glaze bleeds through the piece and leaves a yellow stain on the outside which turns into a light brown. Thicker parts of the piece don’t show the stain as the glaze probably isn’t permeating all the way through
Has anyone run into this before or have any ideas on how to prevent/clean up the staining?
I’ve run into this before, especially with light clay bodies, but the yellowing always burns out in the kiln. Are you still seeing staining after glaze firing?
I love your piece 
Thanks!
Typically, the majority of it burns out, but the parts that don’t turn into a tan/light brown.
Hmmm, do you have any pictures of the tan/ brown staining after firing?
I’ve had some shadowing show up on my final pieces when I have bare clay (the mug below was fired at a different studio, also cone 6 electric, buffalo wallow). In that case, I think it was that the pieces were packed tightly in the kiln and there might have been some off-gassing/ fuming going on. TBH I like the kind of earthy effect, even if it wasn’t intentional.
Mine usually burns out, but I don’t know that I have every had such an expanse of unglazed clay to show it as well as yours. Perhaps it is iron from the wet glaze traveling through the dry bisque clay body as it is absorbed and evaporates. I wonder if it would help to wipe the areas that won’t have glaze with a wet/damp sponge to try to slow down the traveling on those areas you want to stay pristine? Worth a try on a test piece. I’d be interested to see if it helps at all. ETA: have you had this happen with other glaze colors?
Would be curious to know if in the example piece (fired) was the discoloration isolated to that area pre glazing firing? I’ve seen bisque go yellow in places frequently (like in your first photo) but it always burns out in the glaze fire for me. I would also be interested to see how the outside looks after firing for that piece in the first photo (I’m assuming it has only been bisque fired).
Do you mean wipe down the outside with a wet sponge before glaze to saturate the clay a bit? Will definitely give it a try.
I haven’t tried only glazing the interior of pieces with anything other than clear. But I’m going to try white or ivory next.
Correct, the first photo is only bisque fired. I can post the glaze fired photo tomorrow when I’m at the studio.
Yes, I was trying to imagine ways to stop the moisture from getting all the way to the outside or at least slow it down somewhat. Alternatively, I wonder if wax would penetrate enough of the clay to stop the stain from getting to the visible outer layer.
One other bit of info that may help is how you’re getting the dip glaze into only the center of the pot.
Due to the way some glazes behave, it can be hard to get a truly even blending of ingredients if not actually dipping the piece.
alternatively- decant off a small portion of it, and add cmc gum. Should reduce its ability to flow.
This is an interesting idea - do you think that the added CMC gum acts to keep the glaze and moisture more on the surface than actually penetrating the clay?
That’s the hope anyway, lol.
It should help suspend the ingredients on the surface, and slow down the moisture penetration so hopefully things dry out closer to the surface before getting all the way through.
I wonder if it could also help to switch to a different clay body. Cinco Blanco is pretty porous and there are other similar-colored clay bodies that are less so. For instance, Kentucky Mudwork’s Iceman.
I wetted the outside of this piece before pouring in the dipping clear and it seems like it has worked so far. Also, tried to pour the glaze in and out as fast as possible for all of these. Haven’t seen any yellow splotches yet.
This next one was a control. Dipping clear fast as possible, no wetting the outside. Saw a couple yellow splotches
Lastly, I tried glazing the inside with white gloss as fast as possible, and haven’t seen any bleeding through onto the outside of the piece.
We’ll see how it turns out in the kiln 
we love an experiment!
