Last month there was a thread about problems with uneven development using the Yankee tank. Today I developed 8 sheets of 4x5 Agfa APX 100 in D 76 diluted 1:1 for 10 minutes. I prewashed for 1 minute, drained the stained water and prewashed for an additional minute before starting the developer. There is no uneven development on any of the sheets. I don't know if the credit goes to the prewashing or the long development time or both. Years ago using the same tank I did have some uneven development using Super XX and DK 50. I think I did not prewash at that time.