I saw some really cheap silver nitrate on ebay. http://www.ebay.com/itm/ws/eBayISAPI.dll?ViewItem&item=250990041362&ssPageName=ADME:B:WNA:US:1123 Is this useful for alt processes like salt prints? Or do I have to buy the more expensive ACS grade? http://www.ebay.com/itm/Silver-Nitrate-ACS-Grade-99-6-1-Pound-/150654523039?pt=LH_DefaultDomain_0 I don't need a whole pound, but what's the difference? Thanks in advance!