Sanding some old floors using a belt sander, for the most part this is doing a good job.
However, some areas of the floor are covered in a dark-coloured coating which just clogs the sanding belt up in no time. I've tried nitromors but this doesn't do anything. A heat gun and scraper helps but doesn't get rid of it all; what does come up forms a mound of 'tar' on the scraper. What could this coating be and how can I get rid of it? Presumably a drum sander would have the same problems trying to sand it.
I've attached some pics...
However, some areas of the floor are covered in a dark-coloured coating which just clogs the sanding belt up in no time. I've tried nitromors but this doesn't do anything. A heat gun and scraper helps but doesn't get rid of it all; what does come up forms a mound of 'tar' on the scraper. What could this coating be and how can I get rid of it? Presumably a drum sander would have the same problems trying to sand it.
I've attached some pics...