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yo bruise..I have no idea. i am not a metallurgist, linguist or metal head...why do my hands get carbide on them....

but then i was thinking..if JB is only toproping those routes, the rope that is in the gri gri would rarely be the rope touching the rap rings, so my already asinine comment is further eradicated.

Every time you toprope through a fixed anchor, god kills a kitten

I'm no metalurgist either but isn't it aluminum oxide that gets on your hands from the rope running through biners? I get the same thing from ladders.

Sandy wrote:I like the shooting people idea.

Have Gun, Will Belay

JB wrote:the aluminum oxide (gross black stuff)...definitely doesn't saw through the anchors.

http://www.kramerindustriesonline.com/b ... -oxide.htm
"Aluminum oxide is an extremely sharp, long-lasting blasting abrasive that can be recycled many times. It is the most widely used abrasive in blast finishing and surface preparation because of its cost, longevity and hardness. Harder than other commonly used blasting materials, aluminum oxide grains penetrate and cut even the hardest metals and sintered carbide."

cool. thanks for that. maybe i need to call it something other than aluminum oxide, because that can be a little confusing.

i don't believe the "black stuff" that forms on ropes is the abrasive form of aluminum oxide. the alumina used as an abrasive is in crystaline form, and is a corundum, which indeed is used as an abrasive in things like, oh, sandpaper.

the black powedery stuff that forms on ropes is oxidized aluminum of such an incredibly fine grain that it is likely to act more as a lubricant than an abrasive. you're not going to get crystaline aluminum oxide (corundum) from an oxidizing aluminum carabiner.

I always assumed the black stuff was a mixture of aluminum residue, sand/grit and slightly melted nylon from the rope. After awhile your rope will get a slightly glazed feeling, especially if you're a sport rappeller.

Just a thought. I really don't know.

The aluminum oxide doesn't hurt anything other than giving some of us headaches.