Quantity ball clay

[Cumnor]

Hi, I am going to use ball clay to build my WFO, it comes in 25kg bags, very roughly hom many bags will I need for the first layer of my dome.
many thanks

[david s]

That depends on a few things.

1. how big is your oven? Assuming you want to build a hemisphere, to calculate the volume of the dome use 4/3 x pi x r3 then calculate the volume of the sphere using radius of the outside, then do the same using the radius of the inside. subtract the larger from the smaller and divide by 2 because it's a hemisphere and you will have the volume of your dome.
2. Are you casting or using bricks?
3. How thick are you intending to make the walls?
4. Are you using the clay for a cob mix, castable or brick mortar ?