This is related to chemicals USED in a pool, but I had a non-pool-use question!
Soda ash (sodium carbonate) is required for dyeing fabrics with certain types of dye. The site where I buy my dyes has something called DENSE sodium carbonate. I sent them a query asking how theirs was different from washing soda. I received a response but it wasn't very informative.
The "dense" sodium carbonate is somewhat more expensive than washing soda, but not vastly so. I am primarily just curious about it. Is it really different?