Victorian cast iron fireplaces are beautiful and a wonderfully warm source of heat. But restoring one to its original condition can be tricky unless you know what you're doing and what to watch for. To avoid permanent damage treat your fireplace like a great piece of art that you are restoring. Start in an obscure area first, and begin with the simplest of cleaning tools, working your way up.
Lay newspapers or a tarp and clean the inside of the stove first; remove wood or coals and clean surface grime with a wire brush.
Clean the outside of the stove of all surface grime with a wire brush.
Inspect the various components of the stove for damage. Make certain the hearth has an underfloor, another raised hearth directly under the fire and a front, decorative hearth.
Repair any cracks in the fireback with fire cement, using a trowel. Attach the grate to the brickwork with screws or wire loops, if needed.
Check the surround and the hearth for damaged tiles. Replace these or repair them in place, if possible.
Have the flue inspected by a professional chimney sweep to make certain that the fireplace is OK to use.
Clean with the lightest weight of steel wool or sandpaper in an obscure area. Move up to heavier weights, if necessary. Clean down to the bare metal.
Use a commercial grade paint stripper recommended for use on cast iron if paint can't be removed with sandpaper. Use rubber gloves to protect your hands.
Scrape the paint off with a plastic or wooden spatula.
Clean the bare metal with a neutraliser such as vinegar or white spirit. Let dry completely.
Even out the finish with black stove paint, polish with grate polish and seal with a non-flammable hairspray or linseed oil.
Do not use harsh chemical cleaners on the surround and hearth. Many of these surrounds have been faux-painted and are not made from the material you think they are. Harsh chemicals will strip the faux work.