Over treating is not as common as under treating, but can occur as well. Mostly PE’s can be over treated quite easily, especially when treating in-line with the extrusion process. When this occurs the film can reach a dyne plateau. This plateau can actually be less than the actual treat that is achievable when not overpowering with the power supply. With this said, over treating is indicated by “blocking” or after the initial treat (at too high a power level) a dyne level reading that cannot achieve what is expected for the given film. This ultimate dyne level can vary as well based on the additives in the PE resin. The additives (slip, TIO2, carbon black, etc.) can make the film much more difficult to treat.
Under treating also gives you readings of lower than as anticipated dyne levels for the given film and additives. So you see they could look identical. Production personnel need to work with their plants Quality Assurance to check what the applied power levels were at the given treat speed to determine which problem is occurring.