So this is what I did.
Soaked the shells in water, not distilled (though I read it should have been) for 48 hours.
Cooked them for 24hour
Strained and removed cooked shells
Reduced liquid by 80%
Strain through 4 layers of muslin
Strain through a coffee filter or something similar, I used a garden mesh that is used to shelter plants from frosts.
Reduce by half again.
I have a project ready and waiting for it ... Can't wait!
12 January 2015