Re: crushed walnut shells and Tek 500 series scopes
There are good examples on the web where walnut shells are used in blasting applications. For example:
If you are really curious even Home Depot and other big box stores has bags of the blast media. I primarily use the media for removing rust and corrosion from chassis and such. Cleanup is simple using compressed air. Since walnut media does not absorb moisture it will not stick to most items.
As for the hardness of black walnuts, I have a tree in my back yard that produces a hundred pounds or more of drupe each year. The nut is a delicacy for the squirrels and it is amazing how they can grind their way through to get to the tiny amount of nut meat inside. The down side is as the squirrels gnaw their way through the nut it leaves a small rock hard object with razor sharp edges that is a delight to step on when walking around in your bare feet.