Updated: Jul 13
You can find a lot of tips about how to load a kiln to fire your ceramics, but because there are so many different types and sizes of kilns, I've decided to share some advice from my pottery experience.
What kiln are we talking about?
My kiln is Rohde Ecotop 60 S, so it's a 60 l kiln which I find a perfect size of a kiln if you want to glaze fire around 20 medium pieces per week. I don't have to wait too long until it's full or build backlog of unfired pieces between firings. What do I mean wait too long? Well, you would like to avoid firing a kiln that is not full enough because of several reasons.
Energy cost and environmental impact - empty kiln means more firings for the same amount of pieces
Some say, that full kiln helps to distribute the heat more even. I can't really check that, but seems to make sense.
Time, time, time. Remember, that for each firing you need around two days from loading to unloading.
Then, my kiln is round inside, it can fit shelves 35 cm diameter. It's convenient to fire round pieces.
Wait, what? How long does a bisque fire take? How long does a glaze fire take?
Two days??? Well, yes. The firing itself depends on a kiln size, program and firing curve you use. For me it can last around 9 hours for bisque fire and around 12 hours for glaze fire. And then you can't just open the kiln straight away. You should wait until the kiln cools down to 40 C. And, in case of a new, well-insulated kiln takes anything between 30 and 40 hours.
How tight should I pack the kiln?
Bisque kiln can be packed quite tightly, the pieces can touch or be one on top of the other. Remember though that the pieces, although they shrink after firing, expand in the middle of the process, so don't overdo it and avoid placing for example similar-sized bowls one into another, as they may get stuck.
Glaze kiln is a different story, as the glaze needs space to do its magic. The pieces can't touch each other or kiln elements. You'll have to leave around 1 cm between the pieces. If you are sure that the glaze will not dip, something small can be placed below wide part of the bowl.
In any case make sure there is at least 1 cm space from the top of the pottery piece to the next shelf!
How many pieces fit in the kiln?
It depends on the size and shape of your kiln and the pieces you make of course, but that you've figured out yourself I guess :) But again, from my experience and for my size of a kiln, that's a sample of what I could fit at once for a glaze fire:
11 soap dishes/incense holders, 2 small bowls, 4 medium bowls, 5 espresso cups, 3 teacups
2 soap dishes, 1 bowl, 8 teacups, 16 espresso cups
15 soap dishes/incense holders, 2 medium bowls, 11 espresso cups, 2 mugs
12 soap dishes, 1 small bowl, 2 medium bowls, 1 teacup, 1 plate, 8 espresso cups, 4 ceramic mugs
And as many pendants, spoons and test tiles I could fit in between.
What can I use to protect the shelves?
You should always procect the shelves with kiln wash. If you are unsure if the glaze will run a lot, you can use a cookie (a piece of bisque), a piece of old shelf or a special fibre cloth underneath the dangerous piece. Or else... grinding.