FotoDave@aol.com
Wed, 13 Jan 1999 17:54:37 -0500 (EST)
In a message dated 1/13/99 2:35:21 PM Pacific Standard Time,
sanking@hubcap.clemson.edu writes:
> Dave, I don't understand how this happens. Can dichromate precipitate out
> of a solution mixed with distilled water? If so I am unaware of this having
> happened in my own work.
<snip>
> Yes, I use the dichromate almost always for carbon. However, the difference
> between a 1% dichromate solution and one of 3% is a very big deal in carbon
> printing, and the loss of concentration of the dichromate in solution would
> be immediatley noticed.
I had a suspicion (spelling?) why my dichromate precipitated out but wasn't
sure. Now the above is giving me some clue. Did you mix your dichromate to
about 3% strength and dilute as needed?
I followed some suggestion to mix my dichromate at saturated strength. Now my
suspicion is that the weather is much colder now, and the saturation point at
cold weather might be lower than during summer. And you are in Carolina, I
believe, and I am in Michigan!
My darkroom is not heated at night, so the temperature might drop to very cold
at night, so that might be the reason for precipitation.
But I don't know if that's a good explanation. Do others have problem of
saturated dichromate precipitate at all?
> But I don't think Kosar made this point with reference to the strength of
> the dichromate solution, or did he? If he did, please tell me where.
I wasn't sure it was Kosar but there isn't many books that deals with
dichromate in that technical details, so I was guessing it was him. I don't
have Kosar, so I can't check right now. I read it from the university library.
My memory seems to point to his book though.
Also, I believe the Web site of the company that sells fish glue (Norland or
something) has the statement about the amount of dichromate, but the wording
sounds almost exactly the same as the book that I have read, so I think it was
probably a quote or paraphrase.
Dave
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