I've never tried something like that, but here is my idea: I should try
paints that are made for the purpose, ie. textile dyes. They need
fixation, but when you use cotton socks, there will be no problem with
that. Besides, a)socks are stretchy, and acrylics are considerably less
so, b)dyes sit in the fibre, not on the fibre like pigments do. And I
should wash the socks at highest temperature before marbling to remove
all residues of what factories think they need to put into their stuff.