There are a few ways to repair a stone fireplace. You can either use mortar or caulk. If you're using mortar, you'll need to mix it with water until it's a thick consistency. Then, use a trowel to apply it to the damaged area and smooth it out. Once it dries, you can then paint over it. If you're using caulk, just apply it to the damaged area and smooth it out. It's a bit easier and faster than using mortar, but it won't last as long.

You repair a stone fireplace by removing the old mortar, cleaning the surface of the bricks, and then reapplying mortar. First, use a hammer and chisel to remove the old mortar. Be careful not to chip the brick. Then use a wire brush to clean off any dirt or debris from the surface of the bricks. Finally, apply fresh mortar and use a trowel to smooth it out.