The knife-grinder’s wheel

Text 1: Sparks by the pump, by Clara Dunmore

An original diary written in a nineteenth-century voice; a period simulation, not an archival document.

A knife-grinder came down our street this morning pushing a barrow with a great stone wheel upon it. He set up at the corner by the pump, worked a treadle with his foot to turn the wheel, and held each blade against it so that a fan of sparks sprang out over the cobbles. Cook sent me out with the carving knife and four kitchen knives wrapped in a cloth. He tested each edge against his thumbnail before he began and again when he had finished, and charged a penny a blade. The children gathered as close as they dared. That evening Cook sliced the Sunday joint so thin that she declared she could read the newspaper through it.

Give one phrase that shows the knives were much sharper after they had been ground.