Cleaning Ceramic Surface - what abrasive?

[Frank Stacey]

During recent renovations to one of our bathrooms, the outside of the WC bowl has become sprayed with some black dust-like muck which is proving difficult to remove. We have tried cleaning off with typical bathroom cleaners but the stuff is reluctant to be come off. What is the most abrasive "thing" we can apply to a ceramic surface without damaging the surface itself?

[The origin of this mess is a not known. In the early stages of renovation I had to remove on old metal shower cabinet which was so "well" built in that I used an angle grinder with a cutting disc to break up parts of it. This sprayed some sparks (hot metal) around and looks the most likely culprit. Only the ceramic has this mess on it. Formica and plaster surfaces are as clean as ever.]

Frank

[Peter Parry]

If it is from an angle grinder nothing will work. The hot spark melts the thin glass surface on the ceramic and the metal particles embed themselves into the glass. Over time the particles (if steel) will rust as well. The Formica and plastic survive somewhat better as the sparks tend to bounce off them rather than adhere.

If you want to experiment with cures just hold a sheet of glass in the sparks from an angle grinder to create test panel to try things on.

I have a very sad tale about a Triumph 2000 windscreen that turned into an abrasive pad as far as windscreen wipers were concerned after using an angle grinder on the bonnet.

[[news]]

ah, the old triumph 2000 / 2.5 PI. fantastic cars.

RT

[Rob Morley]

The black specks are bits of grinding disk and steel that have welded themselves to the soft ceramic glaze - the only thing I can think of that might improve the appearance is treating it with some sort of acid to dissolve the iron component (which will otherwise rust and cause staining) but I suspect that won't remove all the marks, and even if it did you'd be left with the little craters that have been burned.

[Rob Morley]

In article , "Peter Parry" [e-mail] says... .

Been there, done that - but it was only the inside of a Mini screen, so not so important or hard to replace.

[The Natural Philosopher]

It may be that treatment with brick acid (HCl) will at least get the iron out of the pits. If that is what it is.

I fear it is.