The best way to remove black mastic is not to use it in the first place!! The next best option would be to use some kind of thinner or degreaser and just keep rubbing at it until it goes away. There is no easy way to get rid of it but thinners will make the task a whole lot easier.

Here is a link that might be useful: More wooden flooring advice

If you use a solvent, you will drive the tar deeper into the wood. Mechanical removal with sharp scrapers and then sandpaper is about the only way to do it.

Be aware that some black tar-like mastics contain asbestos fibers.

Hi Donna, I used a hot air gun (about $30) on its lowest setting and metal scrapers for mine. Best done in our long cold Mpls winters... good luck!!!!!