Since I keep the albumen in the fridge, I decided I wanted it to be non-toxic, which also lets me mix it in ordinary kitchen stuff. For 1 liter egg whites (about 4 dozen eggs), I add 30g sea salt and 40ml distilled white vinegar. Seems okay with no odor after a month or so.
To keep it from curling in the tray, don't leave it in too long. It probably depends on the paper and relative humidity, but I just float it for 30 seconds (no longer than a minute) usually.