Tin can saggar firing is a fun way of firing, with no more equipment than a large can with a pop off lid, such as those for powdered milk or milk drinks. Indeed, finding such an empty can may be the most difficult part of the process. The can, a fire and some clay are all that is needed - no kiln, no studio, and no special tools.

The process is very simple - a small bonfire, or ideally a campfire is used - but it also introduces the changes that take place when clay is fired (I used to call the process, tin can raku, because it is so immediate, and the ware is black-fired, but I think the term, tin can saggar fired, is more appropriate). This hands-on way may be more meaningful for beginners, as opposed to bisque firing done in an automatic electric kiln.

In an open fire, red heat is the maximum temperature that can be reached. With a good bed of coals, almost 800ºC is possible, a couple of hundred degrees, or so, below an ideal bisque temperature, but high enough. By this temperature, physical and chemical changes have occurred, and the clay is permanent, albeit soft and fragile.
I was first introduced to the process when we were on a fishing trip for a few days, with three or four children of school age. Upstream a few kilometres, all the trappings of civilisation were absent, but all of the ingredients for a tin can saggar firing were to hand. There was plenty of clay at the water's edge, and away from the mud, simple enough to collect a few handfuls at workable consistency.

It's possible to introduce a field test for plasticity. Roll out a coil snake and bend until it cracks apart - the fewer cracks the better the consistency. Good, plastic, earthenware clay is often signalled by its light yellow or orange colour. Grey clay would have some fine organic matter present, and may also be good secondary clay. In practice, so long as there is some plasticity, the clay will be fine. Because of the rough and tumble firing, objects are likely to have fragile projections knocked off. (I have usually had some back-up prepared clay in the car just in case, but bought clay somehow seems to defeat the purpose).
The process begins with the making - an ideal campfire activity. Animals, especially fish with no fiddly bits are ideal, though, I suppose anything is feasible with care. Modelling is done by hand, or with a knife or other cutlery, or a smooth stick. The sculptures are left by the fire overnight to harden up and dry out. At breakfast, the pieces can be put into the tin, but well away from the coals, and I usually poke a few holes into the lid or sides to let it breathe.

Black swan on nest, and pinch pot, using terracotta

If there is a difficult point, this is it, because a bisque firing steams at 100-120ºC, whilst a naked flame in an open fire is already at least three times that. It must be remembered that clay will only dry to the ambient humidity, and all water must be evaporated. On the second night, the tin is ever so gradually inched closer to the fire. A rattle of clay shards, not unlike popping corn, will signal that the process has been too hasty. This may also be a very good learning process, but hard on creativity. If I am conducting the operation in suburbia, or at a school, I may take the precaution of a pre-heat in the kitchen stove, on low for an hour or so.

When the can is finally pushed into the bed of coals and covered as much as possible, it is left for some time. Cans have a folded, not soldered, seam these days and the steel will take the heat of the firing. When the can has been as red hot as the coals around it for a while, the radiant heat should have been transferred to the pieces inside.
The pieces can be burnished with the back of a teaspoon, or a pebble, again an ideal campfire activity. Some leaves or grass can be included in the tin. These will cushion the wares and ensure that they are smoked black. While it is possible to have the clay come out natural terracotta, or white colour, in practice the tin is at least partly embedded in coals and ash and so some reduction tends to occur anyway.

Rake the tin out with a stick, or even a rake if you must, and pop the lid off immediately with the same screw driver or fishing knife that was used to make the holes in the can. Tip out the ceramics and splash with water until cool enough to pick up. The works are ready for immediate exhibition.

I suppose that there are some OH & S concerns about children and open fires, if the activity is school based. Sensible clothing and closed shoes, proper supervision and good garden gloves are essential for the operators. But, handling fire too can be a good learning process. Over the years, I've fired with people of all ages from senior primary to university - it’s still a good way for BFA or elective ceramics students to be introduced to fired clay. Perhaps the only proviso is that tin can saggar doesn't work well with too many cans in the one fire. The more cans, the larger the bed of coals needed, and to achieve a good bed of coals with a lot of cans the campfire will become a conflagration.

Ray Hearn, 24 Anslow St, Woodend Vic 3442, P: (03) 5427 3916