Removing stubborn varnish

Q: I am refinishing a staircase that has oak treads. The treads were finished with some sort of clear finish that’s about 60 years old. I sanded and sanded until it felt smooth and then stained three of the treads with an oil based Minwax walnut. It couldn’t look worse. Every scratch, mark, and slightly different texture turned black, and the rest hardly changed at all.

I was going to flip the treads over, but they are all glued, nailed and shimmed. When I tried to sand them again, the sand paper instantly clogged with hard melted looking varnish chunks. Is there any way I can get this varnish off?

A: I think I would try chemical stripper first. Then go at it with a random orbit/orbital sander starting from about 50-60 grit, then 80 and if you like, 100. Corners have to be largely scraped by hand. If you want a deeper colour, wet the wood first (not soak) and let it dry, then stain. This “pops” the grain open to receive the stain.

Be careful. A lot of old varnishes also contained lead.