U of S | Mailing List Archive | alt-photo-process-l | white precipitate in VDB

white precipitate in VDB

  • To: "Alt, List" <alt-photo-process-l@usask.ca>
  • Subject: white precipitate in VDB
  • From: "Christina Z. Anderson" <zphoto@montana.net>
  • Date: Sun, 02 Mar 2008 11:44:04 -0700
  • Comments: "alt-photo-process mailing list"
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  • List-id: alt-photo-process mailing list <alt-photo-process-l@sask.usask.ca>
  • Reply-to: alt-photo-process-l@usask.ca

Now I cannot remember who even brought up the problem recently about the white precipitate in VDB, and I think that the person got the answer to his question, but as I sit here preparing an exam for my alt class, I came across (in my own book!) a paragraph that answers the question for me, anyway. I can't believe it--the reason why I didn't find it was it was actually under the salt chapter!

Anyway, this is it--"the sensitizing solution must be made with distilled water, because the silver nitrate will react with chlorine and hard water ions such as carbonates, etc., that exist in many water supplies. The result is a cloudy white precipitate of silver chloride, silver carbonate, etc...."

Now, the last two times I mixed up VDB solution I definitely used distilled water from the grocery store, not "spring" water or some other option, so perhaps this is why I don't experience the problem, not because I heat my water up. The fact, as Judy says, that some "distilled" waters are not, in fact, distilled really kinda creeps me out. I mean, one can imagine that happens in 3rd world countries but on our own grocery shelves?

Christina Z. Anderson
Assistant Professor
Photo Option Coordinator
Montana State University