[pure-silver] Re: b&w print has discolored - re:Richard's comment on washing
----- Original Message ----- From: "Nicholas O. Lindan" <nolindan@xxxxxxxxxxxxx> 
To: <pure-silver@xxxxxxxxxxxxx>
Sent: Thursday, March 27, 2008 2:26 PM
Subject: [pure-silver] Re: b&w print has discolored - re:Richard's comment on washing 



"Janet Cull" <jcull@xxxxxxxxxxxxx>


Here's how I wash my prints. [quick rinse, then
emulsion side up, under a running tap for a "few minutes"] 

Not good...

You may want to consider re-washing all your prints.
Though Richard seems to feel it is a lost cause, and it
certainly may be. At the least test a few with residual hypo tester where you can snip off a bit of border. You may also wish to clean whatever method you use for drying prints. 

Have you collected the running tap water to see how much
water per print your method uses? You may find a tray siphon 
that washes ~10 prints at a time to be more economical.
You need to do residual hypo testing if you use HCA, especially the Orbit, Permawash etc. types. HCA goes bad in 
a few hours [or faster if the stock is old].  The stock
goes bad after a few months.  There is _no_ indication the
HCA has gone bad - well maybe after a few years when the
prints washed in expired HCA all turn odd colors.

See
http://unblinkingeye.com/Articles/Archival/archival.html
for residual hypo test, fixer test (is the fixer any good)
and residual silver test (did the fixer remove the silver). 

It is important the water used for washing is 70 to 85F.

My present darkroom doesn't have running water.  Well it
does, in the sense that I run with the bucket. My method is sparing on water. It uses a deep wash tray [called a 'hypo tray' at B&H], agitation and periodic changes of water. There are as many methods as people you ask. 

Method:
After the first fix, all prints are held in water in the large wash tray after first fix, they accumulate there until (normally) the end of the session. 

 Keepers are run through a second fix, keep some scrap
 sheets to test washing efficacy

 Large tray then used for the wash -

 2 changes of water, 30 seconds each with agitation
HCA with agitation as needed: 1 minute for RC, 10 minutes for FB.
Take to bathroom and rinse under tap to remove 'soapy feel' 

 Prints back in the large tray, with occasional
agitation and water changes at increasing time intervals until prints test clear for hypo
I wash till the prints test clear, and not for a fixed time: there is no point washing the prints after they are free of hypo; and there is certainly no point in continuing with prints that still have hypo in the emulsion/base. 

== Nicholas O. Lindan
Cleveland Engineering Design, LLC
Cleveland, Ohio 44121
The important thing is that the water at the surface of the print be fresh. This is increasingly important as the hypo washes out because it is a diffusion process and the rate of diffusion depends on the difference in concentration on the two sides of the emulsion. As the hypo washes out the concentration in the emulsion goes down so the wash water must be free of hypo for the process to continue. There are two standard tests for fixing and washing. For fixing the test is the residual silver test. This can be done with a 2% solution of sulfide or a 1:9 dilution of KRST. The KRST solution is longer lasting but fails where there is much residual hypo in the emulsion. Both are used in the same way. Place about 2 drops on wet but blotted emulsion surface and allow to stand for about 3 minutes. Blot or rinse off and look for any stain. There should be no stain if there is no halide. The test must be made on a clear portion of the print or film and is best done on a scrap of fixed out film or paper processed with the regular run. The residual hypo test is done with a solution of silver nitrate in a preservative, usually acetic acid. It is done much like the above and will leave a brown or yellow stain which will be darker in proportion to the amount of hypo left in the emulsion. Some emulsions will show a very slight yellow stain even when hypo free. Kodak used to publish an overlay called a Hypo Estimator with chips of colors to compare with the stain but I suspect it has been long discontined. The test solution formulas are available in several sources including the _Kodak Black and White Darkroom Dataguide_ which I believe is still being published. Fixing for paper (including RC) or film should use the two bath system. The capacity of a single bath to completely fix paper emulsion is very limited. Ilford estimates it at no more than 10 8x10 prints per _gallon_. If two successive baths are used the capacity is multiplied by four to ten times. There is no simple way to measure the amount of dissolved silver in a fixing bath. A very rough mesurement can be made using a solution of postassium iodide. This is what commercial products like Edwal Hypocheck are. When the amount of silver exceeds a certain amount the test forms a permanent cloud of silver iodide. However, the amount needed varies with the strength of the solution and, IMO, is too high for archival purposes. Note also that the capacity of fixer for film is usually greater than for paper. About the only reliable test is to mesure the amount of residual silver in the emulsion using the toner tests as described above. There are more sensitive tests but they are too difficult for routine home use. The capacity of "rapid" or ammonium based fixer is somewhat greater than sodium fixer but neither is very high in a single bath. The use of a sulfite wash aid like Kodak Hypo Clearing Agent can extend the capacity of the fixing bath(s) because it makes soluble some otherwise insoluble fixer reaction products. However the use of KHCA or other wash aids for RC is questionable and not recommended by Kodak because even with the problems of washing after fixing with an acid hardening fixing bath the rate of washing for RC is very fast. However, if you are going to tone completely in a sulfiding bath this probably is not relavent because the toner will completely stablize the emulsion. There may be an advantage if you use the bleach and re-develop type toner and find you have some reduction in maximum density from the toner. The bleach can act as Farmer's reducer if there is much hypo in the emulsion causing some permanent bleaching. I have not found this to happen with a normal four minute running water wash. Another method of checking the rate of change of water in washers is to put some coloring agent in the water. I used some of the juice from canned beets. The color should be visibly gone in no more than four minutes. Very few so called archival washers will do this. I have a Zone VI 16x20 washer and run it in the bathtub allowing some overflow and also use the tap to empty it once or twice in the wash cycle. There are better vertical washers that use less water and have a shorter change time. A tray syphon in a 16x20 tray is much faster but can be used for only one large print at a time. It is quite satisfactory for RC but I use it mainly as a holding tray for fiber. 
---
Richard Knoppow
Los Angeles, CA, USA
dickburk@xxxxxxxxxxxxx 
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