Well, the simple answer is as long as it takes to remove all of the water.
When I started in this biz, I printed yardage on long tables, with waterbased inks. We were able to set it with a normal hand iron.
I also have used a waterbased ink from Union that with a catalyst would dry enough to handle in a couple of minutes, and fully dry/cure in a day at room temp.
Now, as for using waterbased inks on shirts, even with a conveyor dryer, one with circulating air is best to aid in the removal of this vapor.
With plastisol, we are merely bring the ink layer up to cure temp.
All this said, with luck, someone who has also tried this will have some real-world advice.
