Paint remover takes off old varnish

Q: I'm refinishing the stairs in my turn-of-the-century home, and when I pulled off the carpet I found this black stuff underneath. I don't think it's paint. What could it be?

A: This could be one of two things.

It could be shellac, which would be easily removed using alcohol. But the black substance is probably a varnish that was popular to use on wood in the era when your house was built. This varnish is thin and doesn't penetrate the wood, and will be easily cleaned with a mild paint remover. Question and Answer