[pure-silver] Re: fix good?
- From: Mark Blackwell <mblackwell1958@xxxxxxxxx>
- To: pure-silver@xxxxxxxxxxxxx
- Date: Wed, 6 Feb 2008 18:39:31 -0800 (PST)
Of course this is always the case. It was my last package, so no more to remix
tonight and I need these few rolls done tonight. This was powdered an of
uncertain age. Found one more container that is clear, but also of uncertain
age but clear and hypo check shows no build up. I am going with that for
tonight and see what happens and hope for the best. In the past if its gone
bad there have been some visual signs and this container had none.
I did have film in the camera at least. This time anyway. lol Never ceases to
amaze me at how easy it is to foul up if you don't think before you do.
Richard Knoppow <dickburk@xxxxxxxxxxxxx> wrote:
----- Original Message -----
From: "Mark Blackwell"
To:
Sent: Wednesday, February 06, 2008 3:48 PM
Subject: [pure-silver] fix good?
> Well after a while I mixed a batch of fix only to forget
> to turn down the water temp, and its now a very milky
> white mixture in appearance. I have mixed fix with
> water too hot before and it always seems to clear when it
> cools off
>
> Would it likely be ok to use this as is? Could it be
> used, as a temp fix and then refix the negs later as
> insurance?
>
> This might also clear, but I tried to help on portion of
> it along in the cooling process but it didn't seem to
> help.
>
> Any help would be appreciated.
>
I think its possible the heat may have caused the
thiosulfate to decompose. One of the steps in making
alum-hypo toner is to subject a mixture of hypo and alum to
high temperature water (above 160F) to get the hypo to
decompose. The sign of the decomposition is a milky
appearance.
Most old fixer formulas specify crystalline hypo which
is endothermic when it dissolves. That is, it cools the
water and is difficult to dissolve if the water does not
start out hot (Kodak specifies 125F). However, anhydrous
hypo has little heat of solution and should not be mixed
with water over about 90F. I am not sure if ammonium
thiosulfate is similar but its usually available as a liquid
concentrate because the powdered type does not have a long
shelf life. In any case, hypo is pretty cheap so IMO its not
worth taking a chance on it.
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx
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