In reply to GrahamD:
slightly off subject, I have owned some pretty rank climbing chalk.
How
Well, when I was a student I was, of course, skint. A mate of mine reckoned he could get climbing chalk for free of his old man.
so the next week he turned up at the Richard Dunn wall ( lots of nice inset polished rock in a DR wall) and we all took our fill of his unending supply of white stuff.
Off I trotted, and did my party piece which was a traverse of the top wall, about 30 foot above a wooden floor. I dipped nervously into my chalk bag and went for the polished sloper, The next thing I know I was plunging sideways, my bowels went loose and I just about managed to keep my left crimp. Shitting it, I down climbed and asked my friend WTF was in my bag.
"chalk" he replied "from my dad's engineering workshop"
Turns out he had given us some sort of silica which is used as a dry lubricant and in turn made your fingers into teflon.
Happen I might put some in FH's bag next time he does TPS.