How do I know that my prints are archival?
Basically you will have to trust the honesty of the printer. Most printers are honest, they depend on repeat business from their artists and will not take a chance of a print failing. It not only costs them money to reprint it, but word travels fast in the art community. Produce a bad series of prints and you are out of business.
Ask the person doing your printing what paper/canvas and inks they use. They will tell you and you can check out the products using Google. There are only so many manufacturers of the products we currently use. I for one have used Hawk Mountain Papers for almost 10 years. It is an American made paper.