Removing layers of shellac, varnish and paint

Q: I am refinishing 112 year old fir plank floor in my farm house. These floors had received many different finishes over the years, including what appear to be orange shellac, varnish and paint. I am having difficulty in fully restoring the floorboards to an even colour, free of any trace of previous coating.

Should I just continue to sand the floors aggressively with a drum sander and edger prior to finish sanding?

A: I would have strongly encouraged you to hire someone experienced in the use of professional sanding equipment (which, for the most part cannot be rented from a rental). Having said that, all of the previous coating should be removed either with chemical strippers or sanding machines down to the bare wood. It is possible that some trace of paint may remain in some parts of the board. I have just used Waterlox tung oil finish for the first time, and it may be a good option for you too.