Details matter! The image is of the gap between the kiln shelf & the bottom of the pot, which is raised up by three wads of high-refractory clay material (called wadding*) which prevents the pot from sticking to the kiln shelf when the soda coats everything in the chamber with soda glass. After the firing, the wadding just pops off, leaving pale marks where it previously stuck.
I find the higher this gap is, the more glaze gets deposited on the bottom, creating some color & sometimes a bit of shine. The wad marks - pale dots where the pot rested on the wadding where no soda vapor could get deposited - are often quite handsome.
|Wad marks on a mug|
Because the wadding is basically wet clay, the weight of the pot tends to squish it almost flat. It will still do its job of preventing the pot from sticking to the shelf, but the bottom won't get any soda, so will just be white. Not the end of the world, & not the end of the pot, but I do like the ones with more distinct wad marks better.
To achieve this, I find I have to make the wads ahead of time, so they are a bit drier & stiffer when I place them on the pot. I can't make the wads too early, because if they dry to much, they won't stick to the bottom long enough to get the pot into the kiln. Like a lot of things in clay, the pots are fine if I don't do it, but they are just a little bit nicer when I do.
Speaking of things that I should really remember to do ahead of time: I was supposed to fire today, & I would have, except my cone packs exploded! Regular readers must get tired of hearing all the ways I manage to screw up, but maybe you can draw inspiration from it: If a ginormous fuck-up like Lori can do this, so can I! Actually I don't know if I screw up more than most people, but since I am a ceramic educator as well as a potter, I believe in being open about my mistakes. I make em! A lot. But then I fix em & move on.
|The culprits. You can just tell they are plotting something.|
I fixed the exploded cone pack by unloading the entire kiln to dump out the little bits of debris inside the pots, then reloading the whole thing. I was mad at myself at first - the exploding cone pack was definitely caused by my dumbness - but it's summer in Maine, I was outside, the birds were singing, & loading kilns is fun! If that's the worst mistake I make this week, I can live with it. Anyway, the last firing was absolutely picture-perfect, the cones falling in synchronicity, so I was overdue to have a Murphy's-Law firing.
Anyway, once I got over calling myself a moron & started enjoying the work, I decided that, far from a moron, I am in fact a genius! (LOL ALL DAY) Or at least reasonably clever in this instance, as I realized that when I scheduled the firing I built in some time in case something goes wrong! So I'm still on schedule.
Barring some other mishap, I'll be firing this load on Friday, probably unloading Monday. I hope to have new work in the online shop on Wednesday!
1/3 Alumina Hydrate
1/3 Coffee Grounds