Coffee might be the most useful single ingredient in the ceramic process!
I mean, besides clay, of course. Oh and silica, and those other glaze materials. And propane. But coffee is pretty useful: I've saved a bunch of money after a reader suggested putting the grounds in wadding in place of expensive grog. Makes a better wadding, too: softer, so it comes off more easily and is less likely to leave a scar. Since that worked so well, I started putting it in door mud also, reasoning that the air spaces created when the grounds burn away would make a more insulating mix than the straight alumina/ fireclay mix I had been using.
Not to mention my climbing rose. I've been mulching around it with coffee grounds, and it's growing like a mad thing.
It helps get the potter in gear, too.
The only downside is, it stinks. Not at first (and not on the rose), but the next firing, the mix will have a faintly pukey smell. I'm not good at guessing exactly how much wadding or mud I am going to need, and I hate interrupting myself during the loading to go mix wadding, so I tend to overmix. I am loathe to throw any away - still got my World's Cheapest Human trophy - because I can use the leftovers next firing.
The extra wadding can just go into a ziplock, and then into the freezer. The door mud, though...
Last time it smelled bad enough that I really did throw it away. So, new plan! after the last firing, I left the batch of mud uncovered in its bin, so it dried out completely. Today I will add water and try to rework it, and see if the odor was inhibited.
If you haven't guessed, I am gearing up for a firing. I had planned on firing today, but that ain't happening, and tomorrow and Tuesday I have to be in Portland to teach classes, and Wednesday is my birthday, which equals FLOAT TRIP!!! So I guess that means the firing will be on Thursday, unloading Saturday.