Thanks for your suggestions on chemicals and warnings against drum sanding. I went shopping Monday morning for chemicals, and in the meantime Mr. Weedy made faster passes on the floor with the sander to avoid heating up and globbing the shellac or whatever was on the floor. Results: Denatured alcohol did nothing. I tried wiping with a rag, scrubbing with steel wool, flooding a small area and letting it sit, all with no results. Guess it's not shellac. I then tried lacquer thinner. Scrubbing with a rag seemed to have an effect, so I did a fairly large area. Once it dried, however, there was minimal results, and less so on the unsanded wood than sanded. I tried it in one of the bedrooms that had a single sanding pass, and quit once I started feeling a little stomach cramping. :-) Yes, I had the windows open and a fan going. Sanding that didn't seem any different from the area I didn't apply the lacquer thinner. Didn't try the mineral spirits yet. In the meantime Mr. Weedy had sanded one of the bedrooms about 18 times with 60 grit (seemed to create more dust than 20 grit), and made headway. I took an orbital sander with 40 grit to the spots left behind (slightly deeper grooves/dents) and here's where we're at: Bottom left corner is where I hand sanded. Lowe's had no oxalic acid, but we've got some in our garage 100 miles away, so we'll work on the kitchen again later. Also, in the meantime, we used a belt sander on the mosaic inlay portions to get off the lippage, machine sanded over it to even out the belt sander marks, and then chipped away with a hand sander to get the residual off. This shows what our eventual goal is, but it'll be dozens of hours if we have to hand sand off this finish. I've done some more googling and may try citrus strip or Formby's furniture restorer to remove the finish. We've also got this area that had tile over it. The thinset seems to have bleached out the wood where it touched, but even aggressive hand sanding is having a tough time evening out all the discoloration. I'm still very open to additional suggestions to attack this. And I must say that I now know the answer to the question, "why would anyone cover up hardwood floors?" Anyone who asks has never personally refinished them. :-)

My 1934 old house had had a fire before I bought it. I was told to use terpentine and linseed oil mixture, it looked really beautiful..I sanded it first. Danish oil also looks beauriful on old wood. Stains? You just have to sand first, then use a stain darker than the original. Use a wood conditioner first, then hand stain the wood, trying to blend around the stain until the spot on the floor blends in better. Apply 2 coats of poly. Keep the room as dust free as possible. I still have a dark spot on my living room floor that was burned. Doesn't bother me, just reminds me that this old house has a story to tell.

It's splintering and cracking because it's maple - hard, durable and brittle. And prying boards up is guaranteed to destroy them. You have to remove them by reversing the motion it took to install them. The screws look like the easy way out, and the least expensive, if you haven't reached the point of no return on the removal. If you want to salvage the wood - and it's selling for $5+ per square foot as salvage - buy an oscillating multi-tool and several metal-cutting blades. Slice through the nails under the boards and coax the board loose. If you can work from the side with the tongues, the nails are accessible and the boards easiest to remove. It's faster, and easier and saves more boards. Remove the molding and use a wood-cutting blade on the multi-tool to slice out around the cabinets, but accept that it's going to be difficult to impossible to do a clean job, and the new floor will abruptly end at the cabinets. If appearance matters a lot, remove the cabinets, take up all the floor, put down the new floor and re-install the cabinets.

I had the exact same issue. Initially they thought they could do it. But my house is old and when they did the demo they said the way they did the spacing of the supports under the wood on the older section cannot be duplicated today and the floor would never look even and the old section would always be a little higher and "squeaky". Ended up doing the whole floor. However, the hallways are old hardwood as well and the transition (via a doorway) seems fine.