Question about cleaning copper packing

[groundhog47]

Hey I have been trying to clean up my copper mesh packing today. It has got fairly dark and I noticed a Metallic type flavor in my spirit last run and packing has started to have a funny smell even when I wash it between runs it keeps that little bit of funny smell so anyways I have 5 pounds of citric acid started out with 4 ounces per gallon ended up soaking some packing for 1 hour and it still is somewhat dark. Have I got ripped off on my citric acid or what because everything I read says it should clean up in miniutes not hours any ideas?