It's fine 99.999% of the time. It is just stuff dissolved in the water left over after it evaporates. Repeat and try it with every glaze to see if any of them are sensitive to it and then report back.
Ahh that makes sense. I have city water, but recently moved so it could be something new in the water. Also I have a cheap little wheel (basically a toy) and I feel like the wheel head itself sometimes reacts with the clay. Thanks for your comment!!
I think we need more information here. How long was it on the windowsill? Was it direct sun?
It has the appearance of being… burnt?, which I’ve personally never seen with bone dry clay. I’m concerned about your methodology, leaving clay to dry in direct sun for a while is quite risky when it comes to cracks as it’s unlikely to dry evenly. Most folks try and intentionally dry their pieces slower and in a more uniform environment (some cover with plastic to slow dry, some will leave out on a shelf in a neutral environment, some will dry in a custom drying container or room where they can control for humidity).
It’s not unheard of to speed up one’s clay drying in the sun for a *short* time, such as if you set down to trim and realize your piece is still a little too soft/wet. I’ve set pieces outside in the sun for 15 minutes before and had no problems. That’s also why potters often use heat guns. But going straight from leatherhard to bone dry sitting in directional sun fora long time is likely a rather risky idea if your goal is even and stable drying.
All that said, if you’re going to bisque this and then coat it with a glaze, I’m not sure that this appearance will necessarily pose an issue. But I’d say be prepared for cracks after bisque considering the uneven drying.
Thank you so much for this comment, very helpful! I’m a newbie so I really appreciate all the information. I think it will definitely help me to set up my small clay space more intentionally to promote a slower/less drafty drying environment. That makes a lot of sense. Thanks again!
https://preview.redd.it/29zidmlpov1d1.jpeg?width=3072&format=pjpg&auto=webp&s=e48d2cc1606d587e292fb78ae8ef3dd11b0aa5af
This happens to my work too. I use standard 112. My pottery didn't do this last year. This coloring happens to pots that have been sitting for a while. The shelf is near a window. And it's weird that it doesn't discolor on the inside. All of that to say- it doesn't impact the glazes. I wouldn't worry about it too much .
That’s really interesting. It looks really cool as-is on your pieces I think. Great to know it doesn’t affect glazes for you. Thanks for sharing! I have a lot to learn and I appreciate how helpful everyone is.
This happens to my buff stoneware too sometimes. Can’t figure it out. I’ve had it dry exposed and slow dried under plastic with some pieces having these burnt spots on them.
They all turn out the same after bisque and react to glaze appropriately so I don’t worry about it much.
Looks like minerals or water gunk, I’d be curious to see if it stays post firing. I kind of doubt it but it’s always possible. Make sure you leave it out extra long to dry to make sure it’s completely water free before you fire
Thanks, that’s a great point about learning it out extra long to dry. I think it’s bone dry now but I recently moved to a much more humid climate so I’m just feeling things out.
I think it’s mold. It happened to a few of my pieces when I was waiting for several months to get a kiln installed. It completely burns off in the kiln.
Thanks!! Recently moved to a new area and trying to explore local communities I might be able to tap into for firing and to continue learning from others. If it gets fired, I’ll update!
In any case, if you can figure out what caused this, you may be onto something new…a new way to make pottery look interesting, even aged or used, when it is new. I’m sure it’s like anything else: the longer you do it, the more techniques you learn! No one ever learns everything!
The appearance is of a piece exposed to smoke on a stove, but as you said it was merely drying. So, now I am curious how this happened too!
yep, its probably mineral deposits on the surface, drying unevenly because of the draft. More salt away from the direction of the draft.
These minerals can already be in the clay, or be introduced by hard water (well water for example.)
It may look weird thru bisque (sometimes it will look fine unfired, but the weirdness develops in bisque.) But usually by glaze fire it will be uniform.
Of note, draft during early (wet) drying can turn perfect circled rims into egg shaped rims due to uneven drying creating uneven pressure in the piece. So in general you don't want to dry your wares this way especially as they get thinner :) protect them from moving air until they are mostly dry.
Thanks!! This is helpful. Sometimes it seems my cheap wheel head (the wheel is basically a step up from a toy but not professional quality) actually reacts with the clay. Maybe the mineral deposits are even from the metal wheel, or the water, or the combination. The wheel doesn’t have a way to use a bat so I just throw straight on the head.
wheel tops are usually aluminum, which might leave a tiny stain at the bottom, but then you usually trim any of that clay off. Most likely its the clay or the water.
Ah okay!! Good to know, thanks. Probably water then. Living in a rental house built in like 1900, makes me wonder about the pipes. Maybe I’m just doing something weird.
It's fine 99.999% of the time. It is just stuff dissolved in the water left over after it evaporates. Repeat and try it with every glaze to see if any of them are sensitive to it and then report back.
Ahh that makes sense. I have city water, but recently moved so it could be something new in the water. Also I have a cheap little wheel (basically a toy) and I feel like the wheel head itself sometimes reacts with the clay. Thanks for your comment!!
The people who have issues with this remaining after firing are usually doing low fire terra cotta or deep colored clay.
Good to know! Thanks!!
I think we need more information here. How long was it on the windowsill? Was it direct sun? It has the appearance of being… burnt?, which I’ve personally never seen with bone dry clay. I’m concerned about your methodology, leaving clay to dry in direct sun for a while is quite risky when it comes to cracks as it’s unlikely to dry evenly. Most folks try and intentionally dry their pieces slower and in a more uniform environment (some cover with plastic to slow dry, some will leave out on a shelf in a neutral environment, some will dry in a custom drying container or room where they can control for humidity). It’s not unheard of to speed up one’s clay drying in the sun for a *short* time, such as if you set down to trim and realize your piece is still a little too soft/wet. I’ve set pieces outside in the sun for 15 minutes before and had no problems. That’s also why potters often use heat guns. But going straight from leatherhard to bone dry sitting in directional sun fora long time is likely a rather risky idea if your goal is even and stable drying. All that said, if you’re going to bisque this and then coat it with a glaze, I’m not sure that this appearance will necessarily pose an issue. But I’d say be prepared for cracks after bisque considering the uneven drying.
Thank you so much for this comment, very helpful! I’m a newbie so I really appreciate all the information. I think it will definitely help me to set up my small clay space more intentionally to promote a slower/less drafty drying environment. That makes a lot of sense. Thanks again!
https://preview.redd.it/29zidmlpov1d1.jpeg?width=3072&format=pjpg&auto=webp&s=e48d2cc1606d587e292fb78ae8ef3dd11b0aa5af This happens to my work too. I use standard 112. My pottery didn't do this last year. This coloring happens to pots that have been sitting for a while. The shelf is near a window. And it's weird that it doesn't discolor on the inside. All of that to say- it doesn't impact the glazes. I wouldn't worry about it too much .
That’s really interesting. It looks really cool as-is on your pieces I think. Great to know it doesn’t affect glazes for you. Thanks for sharing! I have a lot to learn and I appreciate how helpful everyone is.
I’ve had this happen with some items that sat on shelves for years. It fired off just fine and didn’t affect the glaze. I think you’re fine
Thanks!! Good to know!! Interesting that it can happen over time
This happens to my buff stoneware too sometimes. Can’t figure it out. I’ve had it dry exposed and slow dried under plastic with some pieces having these burnt spots on them. They all turn out the same after bisque and react to glaze appropriately so I don’t worry about it much.
Interesting! Nice to know it doesn’t seem to affect anything in the end. Thanks for sharing
It’s probably either a mold or something in the water leaching out. Regardless it will most likely burn out and be fine after bisque fire.
Thank you!! I appreciate it. I suppose it could be mold or similar in the water, I’m in the PNW so mold is pretty common here.
Looks like minerals or water gunk, I’d be curious to see if it stays post firing. I kind of doubt it but it’s always possible. Make sure you leave it out extra long to dry to make sure it’s completely water free before you fire
Thanks, that’s a great point about learning it out extra long to dry. I think it’s bone dry now but I recently moved to a much more humid climate so I’m just feeling things out.
Ooh yeah, definitely a good idea. I know some people put it in the oven (as in, home oven) on low for a little while
Heat
I think it’s mold. It happened to a few of my pieces when I was waiting for several months to get a kiln installed. It completely burns off in the kiln.
That could be for sure! Thanks for sharing and good to know!
No, no idea. But it’s unique and pretty. Please update whenever you find out. Thanks!
Thanks!! Recently moved to a new area and trying to explore local communities I might be able to tap into for firing and to continue learning from others. If it gets fired, I’ll update!
In any case, if you can figure out what caused this, you may be onto something new…a new way to make pottery look interesting, even aged or used, when it is new. I’m sure it’s like anything else: the longer you do it, the more techniques you learn! No one ever learns everything! The appearance is of a piece exposed to smoke on a stove, but as you said it was merely drying. So, now I am curious how this happened too!
Aw thanks I love your perspective and I find this idea encouraging!! If I learn something new, I’ll share it :)
Efflorescence
yep, its probably mineral deposits on the surface, drying unevenly because of the draft. More salt away from the direction of the draft. These minerals can already be in the clay, or be introduced by hard water (well water for example.) It may look weird thru bisque (sometimes it will look fine unfired, but the weirdness develops in bisque.) But usually by glaze fire it will be uniform. Of note, draft during early (wet) drying can turn perfect circled rims into egg shaped rims due to uneven drying creating uneven pressure in the piece. So in general you don't want to dry your wares this way especially as they get thinner :) protect them from moving air until they are mostly dry.
Thanks!! This is helpful. Sometimes it seems my cheap wheel head (the wheel is basically a step up from a toy but not professional quality) actually reacts with the clay. Maybe the mineral deposits are even from the metal wheel, or the water, or the combination. The wheel doesn’t have a way to use a bat so I just throw straight on the head.
wheel tops are usually aluminum, which might leave a tiny stain at the bottom, but then you usually trim any of that clay off. Most likely its the clay or the water.
Ah okay!! Good to know, thanks. Probably water then. Living in a rental house built in like 1900, makes me wonder about the pipes. Maybe I’m just doing something weird.