Homebrew PCBs

I wonder if the resist is anything like the Riston blue -Ve acting 
dry film. This film is the main one used by the manufactures here.
It sounds a lot like it.

I have used this resist for many years.

The exposure for this film requires a strong UV light source. A 
standard light would do little in the way of exposing it.

I use a 300W mercury vapor street light at about 300mm. This gives an 
exposure of two minutes. The mercury vapor light produces a fair bit 
of UV light.

With this light source I never have a failure.

I notice you use Calcium carbonate to develop. The Riston uses Sodium 
Carbonate. I wonder If this would work on your resist. Sodium 
Carbonate is also known as washing soda and is very cheap. I think I 
paid about $25 for 25 Kilos. The mixture ratio is about 8 teaspoons 
to 4 liters of water (not the least bit critical). 25KG will last 
longer than I will.

Could be worth a try.

David

David G. Hopkins (Vk4ZF)
CAPALABA QLD.
AUSTRALIA
S27 32.191 E153 11.867