Quote Originally Posted by geraldatwork
There are variations in temperature in different sessions usually less than +- 5 degrees from 68 if that could make the difference I don't know. But if the temperature is cooler I'll keep it in the soup for 3 minutes or warmer than 68 in the soup about 2 1/2 minutes. I develop face down as to eliminate additional chance of fogging and don't even look at the print until I take it out.
A 5 degree change in developer temperature is significant and is likely to be the cause the inconsistencies. The adjustments to development that you quote are guesswork and you should be more precise. There are two ways to deal with this problem: one is to purchase a timer that includes a temperature probe and as the temperature changes it indicates the change in timing that may be required. I know that Zone VI used to have such a timer. The second method is to use the Watkins factor; when you make the first print with fresh developer make a note of the time of the first appearance of tone and then the total development time. You then divide the appearance time into the total development time to arrive at a factor, say 5. Thereafter the appearance time is noted for each print and multiplied by the factor to arrive at the adjusted development time. This is the method used by many of the old time printers when they were printing big batches and wanted consistency. It's crude but slightly more scientific that your guess. Clearly, the first thing you havre to do is attempt to ensure that you hold the developer temperature at consistent levels.