Chilly

This commercially available mug mould (http://www.clay-king.com/pottery_wheels/hump_molds.html) shows the shape the sprue should be. The red line shows where you use a Lucy tool or similar to cut away the excess slip and gives a really clean edge. I have similar moulds, both commercial and home made and they all give a clean edge, and I've never noticed any slumping. You have to be careful not to let the slip be too thick or you risk cutting into the actual mug.

Can you re-read your temperatures. They look way too high for Celsius.

Hi @Emma Law. Welcome from sunny Langdon Hills, about 60 miles north of you. Depending on flatness/size of work, you can also fire on cookies/waster slabs to protect your shelves.

Did you put a cone pack on each shelf? Probably a different temperature on each shelf.

Make a test tile. Like a mini chess board. On each square, do 1, 2, 3 and 4 coats of your medium. Then add a dab of clear glaze in the centre of each square, so some of the medium is left unglazed. Take a photo and write on the photo which colour is where. Make sure you know which is top and bottom. When fired, you will have a reference showing light coats, medium coats, heavy coats, with and without glaze. I could spend a whole lifetime making tests like this. Can also do colour a over colour b.................

And here are the finished vases, not on the workbench, but on the hearth.

I too want to ask this. In the UK, every electric kiln I have used will not work if the lid or door is not fully shut. One, in a school, had a weird key like object that had to be removed from the door lock, and inserted into the controller before the controller would work. And it could only be removed from the door if that was shut. It was a bit of a safety overhead, as a number of times, I would be just about to switch it on and would see a pot that had not got in.

I made some pots a week or so ago and now they're dry. So today's task was to load and fire the kiln. Before that could happen, of course, I had to make space to roll the kiln out from under the greenhouse staging, and into the middle of the floor. So I also had to move stuff away from the kiln, and from on top of the kiln. Also had to lift and store the anti-fatigue mats that keep my feet warm. Then had to sweep the floor. Silver birch seeds get everywhere!

As Johnny says, make sure it is absolutely, completely, totally dry. One problem with drying thick pieces: as the outer surface dries, it shrinks and makes a crust. The inner moisture now has more and more difficulty evaporating to the outside. Fire it very, very slowly so the moisture can escape slowly. Depending on the clay body, you can probably fire it anyway up that fits in the kiln. So long as it is dry.

That's interesting. Mind goes off on a wander - how can I utilise this feature ................. experiments on their way.

Sticking dry clay "chips" back on Eating/drinking in the studio Finessing after I've removed my apron

Is this for a glaze or bisque fire? 1/2" kiln posts is very low gap. If for bisque, have you tried tumble-stacking?

They crumble into nothingness-ish after firing. Maybe, maybe not. I had a porcelain spoon rest (resembled a whale tail) slump to complete flatness. It was born flat under a slab roller, and bent into shape. Next version was born raised (one of my few successful thrown and cut objects) and didn't slump.

Unlikely to bond together. Think how much effort we all go to, to ensure a handle stays attached to it's cup or mug.

What @Hulk said! Front/thicker pot is probably underfired.