Emulsions, depending on the manufacturer, all have different exposure times. Did your emulsion come with instructions? What brand do you have or where did you get it?
I use emulsion from ryonet, it doesnt came with instructions... so im stuck on stupid.
what emulsion is best for water based ink?
Ryonet sells an emulsion for water based ink. They have instructions on their site on how to determine exposure times: Emulsion Exposure Times
Understand, even if you are using emulsion for plastisol, you can still use waterbased ink with it. For a one and done job, there will be no ill affect. It's just once you start cleaning the screens, plastisol based emulsion will start breaking down. But if you are going to use waterbased inks exclusively, it's better to use waterbased emulsions.
Help With Water resist emultion 
