This stuff is in oven pride, but only about 6% of the 'oven pride' solution attacks the ano.
u can buy these pellets from:
http://www.reagent.co.uk/sodium-hydroxide.html11.99 for 500g - pellets are smaller than a pea!
mix about 7 pellets in a an old cake tin and fill it up to about 3/4's with water - stripped a chainring and and brake set in under 5 mins.
it did not go black either because the process was so fast, flushed the items with loads of water, job done!
You can also re use the solution for months - BEWARE however, this does increase the mix to about a 70% solution and it will burn your skin OFF if you are not careful - best done outside for ventilation also (do not stick your head in the tin, breathing the crap in), but trust me there are worst chemicals out there!!!
Have fun!