I took out my knife, opened it, wiped off the blade and pared off the dirty outside surface of the cheese.

By rubbing the sponge against dirty surfaces, the dirt can be removed.

It is designed for cleaning very dirty surfaces, especially washing dishes.

When used on dirty surfaces the yellow brown colour of the iodophor is absorbed and disappears.

On the dirty surface of Sarge's porcelain bathtub I saw everything.

The emission lines are equally affected by 'dirty' surfaces or optics.

With emulsion and masonry paint, painting over a dusty, dirty or loose surface is the cause.

Or the opposite, starting slowly, helps with dirty surfaces, provided the metals are compatible.

The repair materials will not bond properly to a dirty surface.

You might get away with painting over a partly dirty surface - for a while.