Heat register grates are often found in older or historic homes. The grates sit directly on the wall, ceiling or floors and in front of a vent. It lets the heat escape from the vent, but gently directs the heat so that you don't get a blast of hot air. Typically made of cast iron, the grates attract dust, dirt, pet hair and a variety of other debris. Restoring the old heat register grates improves the grate's function by removing anything blocking the grates.
Remove the heating grates from the wall using a screwdriver. Most heating grates have four screws, one placed on each corner of the metal. Push the edge of the screwdriver into the edge of the grate and apply some pressure to pull it loose, if it sticks to the wall.
Lay down a few sheets of old newspaper and place the heating grate on top. Scrub the surface of the grate with a wire brush. Knock loose any rust clinging to the surface of the cast iron and any other dust that might be stuck on the cast iron.
Apply an even layer of the distilled white vinegar onto the surface of the grate. Rub the wire brush onto the grate. Focus on any areas with a thick layer of rust or other debris. Lightly dry the surface of the grate with a dry cloth.
Rub the coarse grit sandpaper over all areas of the heat register grate. Use the sandpaper to loosen any remaining rust and give the piece an even coating. Wipe down with a dry cloth, removing any paint chips or metal dust from the heating grate.
Paint over the heat register grate with heat proof paint, which won't chip or fade when the air pushes through the vent. Wait for the paint to dry and then paint the opposite side, if you like. Use a razor blade to scrape away any paint that clings to the vents in the grate.