Aye kiln dried sand :-/
I am trying for the first time loft granuals, £7 a bag it is a form of deep litter similar to cat litter but for pigeons, I was in Rembrants lofts and it really seemed to be working well, just rake the worst of the top, Chickadee is tired of scaping out every day
I first tried saw dust from the workshop but it was too fine, scattered too easy when the birds flapped their wings
Do not use hard wood shavings, use soft wood shavings as heavy as possible or there is a product called easybed that a lot of fanciers use