I strongly recommend to use readily made photoresist material for PCBs. I further recommend to stay with the brand you have purchased, tested and found good for you.
Using liquid photoresist you end up with a pretty messy work place and NO result at all. Liquid photo resists requires 24 hours of baking at 70°C and a slow cooling period in absolute darkness.
The same applies to Positive20 a sprayable photo resist made by Kontakt Chemie, Denmark.
I prefer to go the somewhat more expensive way (shipping) and purchase photo resist basic material at BUNGARD (
https://www.bungard.de)
Bungard PCBs are the Mercedes class boards amongst boards.
Bungard photo resist has not been changed for years, which means you might omit any dry runs when using different brands of PCB material. The film coverage is even all over the board area leaving no "clouds" after development. "Clouds" can be seen after rinsing the developed PCB with water and dunking it into the etchant for a short moment and checking for shiny areas which are commonly found within large copper areas.
Those clouds take very much time to get etched burying the risk of under etching fine traces and making the board unusable.
My last advise: Don't think to save money when buying cheaply. By the time you've got a successful result you will have
- spent more money for new raw material
- gained more gray hair
- your hair pulled out several times
- and you'll have had several heart attacks (Remember: The fourth one is deadly!
)
- risked the partnership with your wife
- become a stranger for your kids.
Regards
Boncuk