Recently I developed a problem with lines appearing on the abrasive that were not from glue. I didn't think the cherry or hard maple I was using were particularly resinous, so I was clueless. Here are the photos I sent them:
I contacted SuperMax, and here's the response I received:
These black lines are build-up on and in the abrasive. Usually caused by a glue line or resin line in the stock being sanded. Easiest method to prevent/reduce these lines are to angle the stock being sanded. A 30 degree angle is ideal. If the stock is too wide for that, any angle is helpful. Even a 1 or 2 degree angle can dramatically reduce build-up.
As for resin lines, Cherry and Hard Maple are the most prone to this kind of build-up. Again, angling is helpful as is less depth of cut and a faster feed rate than used with other woods.
These lines can be removed with using clear plexiglass on edge as an abrasive cleaner. Or the abrasives can also be soaked in paint thinner or mineral spirits, which will dry out the build-up. Then it can be brushed out with a stiff nylon brush.
If the lines are developing from Cherry or Hard Maple and are not from glue lines, the other option is using a cooler running abrasive such as the blue Zirconium… Please let me know if you have questions or if I can be of any service.
If you need a drum sander, I'd suggest you give this one serious consideration. It's a little more money, but for a lot more tool, and you can't beat the customer service.