There were some posts about rhodium plating solutions getting
contaminated, I came across an April 2007 Stuller Standard, a
monthly newsletter, and there is an ad for a carbon treatment kit for
cleaning organic dissolved contaminates. It is 45-4160 and it is
$69.95. If you do not have an account, you can still put the number
in the search and you can see what the kit contains.
Richard Hart