If you're talking about the one who does them on wood flooring, yes that is
a form of suminagashhi. The main difference between suminagashi and
marblling, to my knowledge anyway, is every other "ring" is done with
either diluted photo-flo or some form of surfectant., and true suminagashi
is done on a water base, rather than a gel base.
My bath get muddy after it's been used for awhile, but not when it's new,
so don't know what you're doing to cause that.
Is this the person you're talking about:
some of them look like suminagashi, some look like marbling and some look
like they have been printed on the wod. Maybe someone else knows more
about the process.
this is one of the better demos I have seen about suminagashi:
don't know if this answers any of your questions or not.
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