Building Box Walls That Meet Cleanly at the Corners
Okay, so we've done bowls draped over molds, which is the forgiving version of shape-making. A box is not forgiving. A box has corners, and corners are where everything you've learned about scoring, slipping, and matching moisture gets tested at the same time, four times over, in the same piece.
I'll be honest with you, boxes were the thing that made me actually good at joins. Bowls hide a mediocre seam. Boxes don't.
Start with a plan, not a slab
Before you cut anything, decide your box's finished dimensions. Draw them on paper. A box has a base, four walls, and eventually a lid, and every wall needs to be cut to match the base exactly, or your corners will be fighting each other before you've joined a single seam.
Cut a template for the base and templates for the walls, same as we did back in the straight-edges lesson. Two walls will be one length, two will be the other length, unless you're doing a square box, in which case all four match. Cut your wall height the same for all four. This is not the place to eyeball it.
Let the slabs firm up together
Here's the thing about box walls specifically: all five pieces (base plus four walls) need to hit that leather-hard, holds-its-edge stage at the same time. If your base sat out an extra twenty minutes while you were cutting walls, it's drier than they are, and you've already set yourself up for a join that's fighting a moisture mismatch before you've picked up a scoring tool.
Cut everything, then cover everything, then check all five pieces together before you start joining. Don't join as you go and hope it evens out. It won't.
This is also where I'll say the thing I say in every lesson and will keep saying until you're sick of it: the air here is dry and it is working against you the entire time you're building. At our elevation, slabs skin over fast, faster than feels reasonable if you learned pottery somewhere humid. I keep a stack of the giant shower caps from Costco next to my work table for exactly this. Not for showering, obviously. I pop one over a wall the second I'm done cutting it and I'm not actively working on it, and I move on to the next piece. It looks a little ridiculous, five leather-hard walls sitting there each wearing a shower cap like they're about to get a perm, but it works better than plastic wrap for anything with a flat top, and it's cheaper than buying the fitted ceramic covers some studios sell you. Nobody believes me on this until they try it. Then they're buying their own twelve-pack.
Joining the corners
Stand your first two walls up on the base, meeting at a right angle. Before you do anything else, check that the bottom edges are actually sitting flush on the base slab. A wall that rocks even slightly will telegraph into a gap at the corner later.
Score both edges that will meet: the vertical edge of each wall where they'll touch each other, and the bottom edge of each wall where it meets the base. Slip all of it. Press the corner together first, holding it steady for a few seconds, then press the wall down onto the base.
Do this one corner at a time, not all four walls up at once and then joining. You want each corner to set up a little before you're leaning on it to attach the next wall.
Once a corner is joined, run a thin coil up the inside seam, the same reinforcement move from a few lessons back. Blend it in with your finger or a rib. This is not optional for me. Score and slip every join, no exceptions, is the one rule I don't bend on in this whole class, and box corners are where I've watched that rule get skipped most often, because people are tired by wall four and just want to be done. Don't. The kiln will find the corner you rushed.
The part where I tell you not to chase perfect
Your corners will probably not be perfectly crisp, ninety-degree, furniture-catalog corners. Mine rarely are. I've made peace with a little softness in the line, and honestly I've come to prefer it. A box with slightly rounded, slightly human corners reads as handmade in a good way. A box that looks machine-precise just makes people wonder why you didn't buy one. Fix actual structural problems, cracks, gaps, walls that lean. Leave the personality alone.
A caution worth stating plainly: once all four walls are up, the box is fragile until it firms up more. Don't pick it up by opposing walls to move it, you'll squeeze it out of square. Slide it on a board instead.
Before next time
Get your base and four walls cut and covered (shower caps or plastic, your choice, but covered) so they're ready to join at the same moisture level next session. If you want to get ahead, sketch what you want the lid to look like. Fair warning, lids are their own fight, and I'm not going to pretend I've mastered them.
~erin