I want to modify a wall so that small magnets will stick, and even hold a small dead weight. I would prefer that the magnetic area not look all that different from the rest of the wall, I don't want to just hang a sheet of steel. I am imagining that 1/4" mesh hardware cloth could be attached to the face of the drywall, and skimmed over with joint compound. We will be skim-coating the walls in any case to get a specific plaster texture.
The hardware cloth I've looked at has 1/4" openings, and is woven from 23 gauge steel and zinc galvanized. Magnets stick nicely to the bare cloth. My concern is that the joint compound will react badly with the galvanization causing the wall surface to check or fail in time.
The wall in question is in a full bath, and so humidity is likely to be higher than in the house in general. One of the proposed locations is directly behind the sink, the other is open wall. We are still discussing the right spot.
Is this a viable approach? If not, what else should I consider?
Update: My intent is to use rare-earth magnets to hold up a glass mirror behind a bathroom sink. The mirror is a 20 inch square cut into seven pieces forming a puzzle. Using magnets to mount the mirror will allow guests to play with the shape of the overall mirror on the wall. My plan is to epoxy three NdFeB magnets to the back of each puzzle piece, or possibly just one on the smallest pieces.
The back of an envelope says that 400 square inches of 0.25 inch glass should weigh a couple of pounds, but I probably should go weigh the actual pieces since Amazon thinks the shipping weight is 4.6 pounds and there can't be all that much cardboard in the box.
Assuming the 4.6 pound figure is correct and that the box accounts for about .6 pound, the smallest pieces would 1/16 the total weight, or about 4 ounces, and the largest pieces would be 1/4 the weight or about a pound.
So the bottom line is that I do need a surface that will allow magnets to hold up about a pound.
Final Update: As all things in a home remodel are in continuous flux, this plan has fallen by the wayside. The answers and discussion have been helpful. I believe the mirror will find a home on a steel-backed whiteboard in the home office, and something more conventional will end up on the walls next to the sink.
I still plan to play with the magnetic primer paint, but from all I've read I'm not expecting it to work out to hold up anything more than a few sheets of paper. With that in mind, the answer pointing to the useful permanent magnet calculator gets the coveted green checkmark mostly because it has been the most useful in guiding us towards a location and use for the mirror.