>> "The main thing to say here is DO NOT USE SODIUM HYDROXIDE for developing
>> photoresist laminates. Use of Sodium hydroxide is the primary reason
>> people complain about poor results when trying to photo-etch PCBs."
>>
>> "It is completely and utterly dreadful stuff for developing PCBs - apart
>> from it's causticity, it's very sensitive to both temperature and
>> concentration, and made-up solution doesn't last long. Too weak and it
>> doesn't develop at all, too strong and it strips all the resist off. It's
>> almost impossible to get reliable and consistent results, especially so if
>> making PCBs in an environment with large temperature variations (garage,
>> shed etc), as is often the case for such messy activities as PCB making."

Patrz. Nie wiedziałem. I używam kreta dokładnie tak jak napisał jacek.
Działa. A skoro działa - po co przepłacać ? :)