Cleaning black stains from redwood
Two suggestions:

Try finding a different supplier. Check out another big-box store, or even better try to find a local lumberyard/sawmill. The local place may well have sawn their own on site and they'll never have been banded, so there won't be an issue. The time saved in cleaning may be worth an extra buck or two that they may charge. It should go without saying that you'd return the marked up wood to its vendor.

Use a plane, jointer or sanding block to sand through the marks. They're not likely more than skin deep, so taking off 1/32&quot; or so is probably all that would be necessary and wouldn't appreciably weaken the wood in any way.


And a third idea based on Graham's answer...

Pressure wash them. We did that with our deck prior to sealing it and all the lumber yard stamps washed right off. Warning: We found it difficult to get a nice, even surface coloration when pressure washing. No matter what I did, some of the surface grey seemed to remain, though most of the wood returned to the nicer, more golden color it started out at.