Back in the 80's I bought quite a few Kodak books and publications. I ran across several of them the other evening and one caught my eye since much has been brought up about developers, agitation methods, etc. This particular publication was called "Practical Processing in Black and White Photography", Kodak publication P-229, inside cover dated 1976.
Page 8 has some interesting info on agitation...
"Agitation is probably the least understood and the most abused of all the development controls. Some individuals use no agitation, while others employ a variety of techniques. Nevertheless, agitation is a simple, straight-forward process that should be used for consistent and uniform results.
When agitation is lacking, a stagnant layer of developer and development by-products forms at the interface of the emulsion and the solution. This stagnant layer is partially depleted in developing agent and is rich in bromide from the developing emulsion. Since bromide is a restrainer that inhibits developer action, the rate of development is retarded unless fresh developer is supplied to the emulsion. On the other hand, if the developer solution is agitated, fresh solution is continually brought into contact with the emulsion surface, and the normal development rate prevails.
Lack of agitation also contributes to another processing problem. Without agitation, the stagnant layer, which is heavier than the fresh developing solution, begins to sink slowly toward the bottom of the processing vessel. As it sinks, it tends to leave streaks on the processed negative. Good agitation overcomes this tendency toward uneven development. It is important, therefore, that the manufacturer's recommendations regarding solution agitation be observed."
There you have it, straight from the horse's mouth.
Page 8 has some interesting info on agitation...
"Agitation is probably the least understood and the most abused of all the development controls. Some individuals use no agitation, while others employ a variety of techniques. Nevertheless, agitation is a simple, straight-forward process that should be used for consistent and uniform results.
When agitation is lacking, a stagnant layer of developer and development by-products forms at the interface of the emulsion and the solution. This stagnant layer is partially depleted in developing agent and is rich in bromide from the developing emulsion. Since bromide is a restrainer that inhibits developer action, the rate of development is retarded unless fresh developer is supplied to the emulsion. On the other hand, if the developer solution is agitated, fresh solution is continually brought into contact with the emulsion surface, and the normal development rate prevails.
Lack of agitation also contributes to another processing problem. Without agitation, the stagnant layer, which is heavier than the fresh developing solution, begins to sink slowly toward the bottom of the processing vessel. As it sinks, it tends to leave streaks on the processed negative. Good agitation overcomes this tendency toward uneven development. It is important, therefore, that the manufacturer's recommendations regarding solution agitation be observed."
There you have it, straight from the horse's mouth.
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