MAKE THE FURNACE

1 Sacrifice a bucket

A metal bucket lined with mixture of sand and multipurpose plaster makes an ideal furnace. Two-thirds fill the bucket with a 50/50 blend of sand and plaster. Mix it well while dry, then add water and stir achieve to a thick but liquid consistency.

2 Insert flowerpot

Find a plastic flowerpot that fits inside the bucket with a gap of roughly two inches all round. Extend its height with cardboard if necessary and push it down into the wet mixture until it’s two inches from the bottom. Weight it in place until set.

3 Form furnace lid

Find a second bucket with a base the same diameter as the top of the first bucket. Make more sand and plaster mix and form a doughnut-shaped lid by pushing a smaller flowerpot into the centre. Add old exhaust clamps to make handy lifting rings.

4 Create air hole

Once the plaster mixture in the bucket has dried, pull out the plastic flowerpot and use a holesaw to cut an air hole through the side of the bucket and plaster at a 30° angle. Aim to have the hole emerge halfway down the inside of the furnace.

5 Rig up air supply

Find a section of steel tubing 2-3ft in length and of the right diameter to fit snugly in the air hole. Work out a means of attaching an air-blower to the end of the tube. A hairdryer, an airbed pump or an old vacuum cleaner set to ‘blow’ will be adequate.

6 Assemble furnace

Insert the air tube to check the fit and angle. Remove the lid from its bucket when hardened and make sure it fits squarely on top without large gaps. Also shown here is a graphite crucible, bought online for £14; other options will be examined next issue.