Tech tip for Black Diamond (and any other polycarbonate base blocks.) Do not use any product that contains:
tetrahydrofuran, methyl acetate, or toluene to clean sandpaper sticky residue off the block.
Polycarbonate is strong, amazing stuff and resistant to many chemicals, but those listed will destroy it.
Just had a customer reach out to me and ask why the polycarbonate base was deteriorating. It alarmed me and I had him ship me back the blocks (I sent him replacements at no cost.) Further investigation revealed that he was using "Grow Automotive 1501 Premium Wash Thinner" to clean the base. That is actually not "thinner" at all, but a chemical cleaner, a very strong one at that.
Here is the chemical breakdown, along with each elements effect on polycarbonate:
In the information sheet I provide with the blocks, I do state that toluene is to be avoided, but there are others and I will update the TDS.
The best thing to use to clean residue off is SPI 710 Solvent Wax and Grease remover.
Or a 50/50 mixture of Isopropyl Alcohol and Lacquer Thinner.
Adhesive removers like "Goo Gone," work as well.
If you are using sandpaper that leaves a lot of residue, another tip is to put clear packing tape (like Scotch Heavy Duty Packing Tape) on the base. The tape doesn't affect the performance of the blocks and the residue doesn't accumulate on it like it can on the polycarbonate.