PREPARE THE GREENSAND

1 Source ingredients

Greensand is available readymade from casting suppliers, but we’re saving money by making our own. We’re using a 20kg bag of fine kiln-dried sand and a bag of plain clumping cat litter, which is basically bentonite clay. Total cost: less than £5.

2 Blend the bentonite

We need to turn around 1kg of the cat litter into a fine powder. Using an old blender attachment on a Kenwood mixer does the trick nicely, though it requires a lot of cleaning afterwards. Beware of the wrath of the owner of the Kenwood mixer.

3 Sieve sand

The grain size of the greensand you’re using defines the level of detail you can hope to achieve in your casting. Seek out the finest mesh sieve you can (60-mesh with holes of 0.25mm is pretty good) and sieve 5kg of sand through it into a clean bowl.

4 Weigh and mix

The proportion of sand to clay in greensand is adjustable, but a 9:1 ratio is a good starting point. Weigh out 4.5kg of sieved sand and add 0.5kg of powdered cat litter, also sieved. Mix the two very, very thoroughly. And old egg beater in drill is ideal.

5 Add water

To give greensand its shape-holding ability, it needs to be damp. Water needs to be mixed in very gradually, so be patient and add it either as a spray or a fine sprinkle. Expect to add between 250ml and 500ml of water. Go slowly from 250ml onwards.

6 Test consistency

As soon as you can squeeze a handful of greensand and get it to hold its shape with a decent amount of detail and density, without sticking, it’s ready to use. It’s slightly too wet in this photo – add more sieved sand and clay and mix patiently.