It substitutes for the sodium with the thiosulfate; it's basically a way of getting something a bit like rapid fixer (ammonium thiosulfate) if you only have access to sodium thiosulfate.
Originally Posted by newcan1
As to the original question, the Kodak docs do say that the pre-blix stop+wash steps are optional for RA4 and that you run the risk of magenta streaking if there is any developer carry-over into the blix bath; it can be avoided with careful squeegeeing in a roller processor but is practically inevitable with a drum. Developer will also raise the blix pH and reduce its effectiveness.
A stop+fix step will certainly help your blix out, but given its price ($2.50/L) and replenishment rate of 10mL/sheet (2.5c!), I really don't think it's worth spending any extra to make a special fixing stop bath. I'm pretty sure that my blix (or I!) will die of old age before it runs out of its 2000 sheet capacity...
Last edited by polyglot; 02-24-2013 at 06:55 PM. Click to view previous post history.