Caustic Soda is Sodium Hydroxide (NaOH). look for this as an active ingredient in domestic "draino" type products. It could be as strong as 90% so be careful with it. Don't breath the dust if you get powder type and keep it off your skin and eyes. Even light dust that floats in the air and lands on your skin will cause irritation if its up near 90%.
Mix it with water at about 1 cup to 20 lts water and soak a sample over night to see if it is strong enough. Keep it away from aluminium, it will eat into it and give off flammable gas. Have a read up about it first so you know what you are dealing with.

http://en.wikipedia.org/wiki/Sodium_hydroxide

Potassium Hydroxide will do the same.