ceramic sinks and wastes

Hi,
having a problem getting a water tight seal on a belfast sink waste?
The surface underneath is uneven.
I've tried plumbers mate to get a seal but its still leaking.
Is it OK to grind the ceramic underneath to get a more even surface?
If so what the best type of equipment to use to do this?

Susanna - this is a common problem with ceramic sinks; it's usually caused because the glaze dripped and collected, before firing, at this area. We've rarely come across one of these sinks that hasn't had this problem.

Solution:

rub down highspots by hand with a carborundum stone, sickle sharpening stone, tile file or even an angle-grinder stone-cutting disc (this last one should be used in your hand, not in the AG. These discs are cheap to buy in, say B&Q).

Use a good quality silicone to seal the fiitings.

Susanna - this is a common problem with ceramic sinks; it's usually caused because the glaze dripped and collected, before firing, at this area. We've rarely come across one of these sinks that hasn't had this problem.

Solution:

rub down highspots by hand with a carborundum stone, sickle sharpening stone, tile file or even an angle-grinder stone-cutting disc (this last one should be used in your hand, not in the AG. These discs are cheap to buy in, say B&Q).

Use a good quality silicone to seal the fiitings.