A Recipe Overwhelmed by One Crucial Variable or a Perfect Storm of Many?
Long story short (too late?). The paper was fogged. Some more than others. The ADOX Art Baryta was least of all. There is a small piece of each uncoated paper next to its coated mate for a color comparison.
Each variable could lead down a research trail.
1. What factors might have changed with a recipe doubling? How much can a recipe be scaled up before its characteristics change?
2. Can the recipe be held under refrigeration at stage before coating?
The answers to 1 and 2 could help address whether or not largescale POP production is feasible.
Do any of the papers have components that fog emulsion? If an offending component can leach out of the paper, can it be soaked out before coating to make the paper safer to coat on?
If a paper has a component which potentially causes fog, could it cause the deterioration of a print over time?
Ripening time is a key emulsion variable. At a specific time/temperature an emulsion reaches it's peak speed. Beyond that point the emulsion can (and usually does) start to fog. The aspirational goal is to ripen right up to top speed and no further. With paper, speed is far less an issue than a clean (completely unfogged) emulsion. What is often overlooked is that ripening continues after coating. It slows down after the emulsion is dry but never really stops. Some emulsions fog much sooner in storage than others. POP is notorious for a short storage life. When I both over-ripened the emulsion before coating and then dried the paper in a very warm room, I almost certainly contributed to the fog. There are several questions generated.
What are the time and temperature of ripening end points for a successful POP emulsion?
Are they different for different POP recipe formulations?
Could reducing the time and/or temperature of the emulsion ripening result in longer dry paper storage life?