As Zumer knows, I've been messing around with scratch boxes lately, and just happened to notice that the piece of white chalk I received with Mr. Shively's Super Yelper has a much different coefficient of friction than the brown chalk I have from Primos.
I think the scratchers sound better with the white chalk than the brown chalk.
Just wondering if you have a chalk manufacturer preference, seems to me while chalk specifically made for friction calls may be oil-free, they may not all be the same.