Cat pee is a vile, destructive thing. Aside from the smell, it's an acid that crystallizes, and the crystals are not soluble in water. It reacts with chlorine bleach, but not in a good way, and it actually burns (scorches) the hardwood floors. The only way to neutralize it is with an enzyme.
So I got some kitty-pee-out stuff in a spray bottle at Walgreens. Spray it on, let it soak in and dry. What is left is a whitish powdery residue that is cleanable with water.
So I did that. About three applications. It did a pretty good number on the smell, but it doesn't reverse the scorching; for that, you need to actually sand the wood down.
So last night I got out the belt sander. I figured it was worth a shot, because the floor is pretty much ruined in that spot anyway.
1.) Sanding a hardwood floor is a hell of a lot harder than one would expect. That's why they make floor sanders specifically for that purpose. I was using 70 grit sandpaper, and it took a couple of hours.
2.) Sanding generates a lot of sawdust. Even with a dust mask, I got sawdust in my nose, and that sawdust was still impregnated with cat pee crystals.
3.) I am highly allergic to cat pee crystals in my nose.
I think that with an actual floor drum sander I could probably sand the floor down enough to get past the scorching, but it would probably lower the floor by 1/8-1/4". That's a lot of sanding. Taking that much off the floor would probably mean having to remove the radiators, and that's not something that I want to do right now. Eventually, yes.
Also, I really don't want to do a major refinish until the cats are gone. In the meantime, I will live with a scorched floor.