I haven't dyed anything since 1976. However, I bought DH a lovely white dressing gown in the same fabric as this (they don't seem to have the dressing gowns available any more). He wears it a lot, and of course it gets grubby fast. He'd like me to dye it blue (well, I suggested it) but I see that dye packets (for washing machines - the dg is big and heavy and there's no way I could get proper coverage by hand) say they'll cover up to 600grammes and the dg is a lot heavier than that. Is it Ok to use multiple packets?