>What is done to an emulsion layer when paper is manufactured, to affect its contrast? >What makes a grade 2 paper different from say grade 5?
Usage slightly different quantity of silver and time of ripening.
> Is it something that is lost when the paper is washed?
If you will wash your paper hard enough, you will wash out some quantity (ver y low, if you will not destroy the emulsion layer) of AgHal and sensitizer.
> if I take an unexposed grade 5 paper and wash it in total darkness before using it, will it still be grade 5 afterwards if I then dry it and use it?
It should not change the grade of paper if you will do it accurately.