A 44-gallon open-top drum with a hole cut out in the bottom to make a furnace. Cut the hole with a cold chisel that is a toughened chisel able to cut steel;

A 16 gallon open-top drum. These are called grease drums and a used one can be obtained from large users of machinery. Cleaning the new drum is easy if the grease has a melting point lower than that of boiling water. Just place the drum on the bricks in the furnace, fill with water, boil and then skim off the oil and grease. If the grease does not shift this way then you have to wipe it out with rags and wash it out with warm, grease-shifting detergent. Clean, open-top drums can be bought online;

A firm round disc with holes in it that fits nicely at the bottom of the smaller drum. A perfect one is the steel disc found across the lint sieve in the older New Zealand Fisher and Paykel tumble clothes driers. If you cannot find one, have a stainless steel one made in an engineering workshop. It needs to be 33cm in diameter drilled with 1cm holes. Do not use weather treated wood as a substitute because you don’t want wood preservative circulating around the jars. Don’t use particleboard as it will break up in the first boiling.

Stiff wire handles that go to just over the top of the drum are attached to the disc. This is the ‘basket’ on which the 24 jars are stacked in three layers of 8 jars.

The drums one inside the other
sitting on the bricks