White Specs in Emulsion

Film Photography & Darkroom discussion

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tmolson
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White Specs in Emulsion

Post by tmolson »

has anyone experienced white specs on the emulsion side when processing black and white film? we are getting these specs that seem to be part of the emulsion (they won't come off). it's not consistent on every roll that we process nor is it consistent on a specific type of film. if anyone has any ideas, i'm open to hearing them!

Digitaltruth
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Post by Digitaltruth »

If the white specks appear on different films, then they must be caused by something in your film processing procedure.

It sounds like the specks are some form or particle, either undissolved developer or limescale/calcium or some other sediment in the water. These particles are probably becoming embedded in the emulsion during the drying phase. Although the latter is the more likely explanation, you should make sure that your developer is fully mixed and in solution prior to use.

To avoid the introduction of solid particles during processing you will need to fit a filter to your water system. For a small darkroom you can use an inexpensive inline micron filter, such as the Paterson Water Filter. If you run a larger darkroom, then it would be worth investing in professional filtration units which can be fitted to your pipework and feature changeable filters.

B&H sell these items: http://www.bhphotovideo.com/bnh/control ... &Q=&ci=522
(the Paterson filter is the last one on page 2)
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Ornello
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Re: White Specs in Emulsion

Post by Ornello »

tmolson wrote:has anyone experienced white specs on the emulsion side when processing black and white film? we are getting these specs that seem to be part of the emulsion (they won't come off). it's not consistent on every roll that we process nor is it consistent on a specific type of film. if anyone has any ideas, i'm open to hearing them!
Are you using stop bath?

Lowell Huff
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Post by Lowell Huff »

If you are using a hardener, STOP. White spects usually is the aluminum dropping out of solution.

Ornello
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Post by Ornello »

Lowell Huff wrote:If you are using a hardener, STOP. White spects usually is the aluminum dropping out of solution.
Nope, that's not it. It's the failure to use stop bath.

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Post by Lowell Huff »

What is the chemical reaction that not using stop bath causes white specs?

Digitaltruth
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Post by Digitaltruth »

A stop bath is not required. Modern research demonstrates that a water rinse is sufficient for most materials unless very exact control is needed. I haven't used a stop bath with film for over 20 years and have never experienced any white specs on the emulsion.

A stop bath is simply an acid (usually acetic acid) which is used to chemically halt the development process. I have heard of problems (pinholes etc...) being attributed to the use of a stop bath because of its acidity, but I have not heard of any problems caused by eliminating stop bath from the processing sequence.
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Keith Tapscott.
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Post by Keith Tapscott. »

Lowell Huff wrote:What is the chemical reaction that not using stop bath causes white specs?
I`m not a chemist, but the white deposits on the negative may be caused by calcium scum. In the `Kodak Data Book of Applied Photography (Volume 3), there is a section titled `Processing Stains on Monochrome Negatives and Prints`(Publication PR-12). On page 4 it mentions calcium stains which are most pronounced with high sulphite weakly alkaline developers such as D-23 developer.
Removal of calcium stains: "The use of a suitable acid stop bath or a solution made up to Kodak formula SB-4, during processing, will destroy calcium sulphite scum which can also be removed by the procedure previously described for the removal of aluminium deposits".
So it seems that the use of a stop-bath is not merely just for stopping development.

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Post by Keith Tapscott. »

Lowell Huff wrote:If you are using a hardener, STOP. White spects usually is the aluminum dropping out of solution.
Could be something in that too. Also in Kodak Publication PR-12:
"Aluminium Precipitates: A white stain caused by an aluminium precipitate can be identified by it`s solubility in both acids and alkalis. It occurs only if an alum hardening bath is used.
Aluminium Sulphite: This is the most common of the alum precipitates and it`s formation can be explained as follows: The usual acid-hardening fixing bath consist of a mixture of alum, acetic acid, boric acid, sodium sulphite and hypo. When alkaline developer is carried over by the material and as soon as the acidity of the bath falls below a certain critical value, aluminium sulphite precipitates from the solution and turns the bath milky. This forms a white sludge, which settles on the surface of the negative or print and is not removed by wash water.
If a stop-bath is not used, only a limited number of negatives or prints can be fixed before the critical point is reached and the precipitation of the sludge commences".

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Post by Digitaltruth »

From Keith's references, it sounds like calcium or aluminium deposits may be the cause, so I would certainly agree with Lowell that by not using a hardener you will stop the aluminium being introduced altogether.

Most of the literature which encourages the use of hardeners is based on film stock from many years ago which used to be much more susceptible to damage. Modern film is highly resistant to damage and rarely requires hardening.

The reference which states that stop bath can destroy calcium stains (Kodak Publication PR-12), also states the following:

"...it is usually removed in the acid rinse bath or acid fixing bath. Consequently it is seen on the finished negative or print only if these baths are insufficiently acid as a result of exhaustion, and if the material is imperfectly swabbed prior to drying."

This publication is quite old, dating from the 1960s, and calcium scum is less likely to be seen in modern formulas, some of which contain an anti-cal agent. The article refers to calcium deposits as being a "scum" and appearing in to look like fingerprints. I have seen this type of residue before, and it should rinse off modern film stock very easily during a normal washing procedure and can be wiped off with a chamois when wet. Perhaps if you are using a specific developer, such as D-23, then you many need to introduce an acidifier, in which case a normal acid fixer should dissolve the calcium just as effectively as a stop bath.

To sum everything up, I would follow the suggestion that you eliminate hardener from your processing sequence if you are using it. Make sure all of your solutions are fresh and your tank is completely clean. Use a filter to ensure that no particles are introduced. If you are using an acid fixer, make sure it is fresh.
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Lowell Huff
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Post by Lowell Huff »

Kieth:
The "hard water" deposits you describe are another reason why we manufacturers have made our formulas with additional water sofeners. The ancient formulas that everyone seems to think are so fantastic, do not have the level of sophistication or advantages that the modern formulas have.

Ornello
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Post by Ornello »

Lowell Huff wrote:What is the chemical reaction that not using stop bath causes white specs?
I'm not sure, but I had the same problem. I went back to using stop bath and the specks disappeared.

Keith Tapscott.
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Post by Keith Tapscott. »

Lowell Huff wrote:Kieth:
The "hard water" deposits you describe are another reason why we manufacturers have made our formulas with additional water sofeners. The ancient formulas that everyone seems to think are so fantastic, do not have the level of sophistication or advantages that the modern formulas have.
Agreed, some of the latest rapid fixers by some of the German manufacturers such as Labor Partner and Tetenal are even claimed to work at pH neutral.

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Post by Lowell Huff »

Alkaline, neutral, or acid pH of fixer, other than processing time, maybe, and some personal preferences, there is no scientific data to support that one is better than the other. The biggest advantage of acid fixer is in machine processing. It is buffered against developer carry over and no stop bath is required because it is a stop-fix.

Ornello
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Post by Ornello »

Lowell Huff wrote:Alkaline, neutral, or acid pH of fixer, other than processing time, maybe, and some personal preferences, there is no scientific data to support that one is better than the other. The biggest advantage of acid fixer is in machine processing. It is buffered against developer carry over and no stop bath is required because it is a stop-fix.
I believed this too, until I started getting spots when I started skipping the acid stop bath and using water only. When I went back to using stop bath, the spots disappeared.

Use stop bath and fresh rapid fixer with hardener.

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