I know smarter people will be along, so I'd like to hear their answer. But, I'm positive somewhere I read that cure #1 & #2 shouldn't be added to hot water because it deactivates them....or something like that.
Like I said, someone will be along with a more thorough answer that I'd like to see also.
It is scary how many TV cooking shows have the house Chef mixing Cure #1 into a big pot of boiling Brine. I saw one for a Corned Beef/Pastrami brine that the Chef said to simmer the Brine for 30 minutes to extract the spice flavor......JJ