sintered glass funnel

[catfish]

WTF? SWIC can't figure out how to get out these stains. Was gotten used and chipped on the bottom and would like to send it off to bee repaired, but clean. How much abuse can one of these things take? It's about 4 inches across maybe 8 or 10 long. If this is the wong place to post this, don't flame.

[Rhodium]

They are pretty delicate, so please don't abuse them too much. What does the stains consist of? Sucking chromic/sulfuric acid through them works good, as does persulfate/sulfuric acid for organic stains, for inorganic you need to know what it is, or use aqua regia.