Occasionally after a cleaning we get the question..."why does that pane look so bad?" Nine times out of ten it's a broken seal.
If a seal breaks, moisture seeps in-between the glass and forms a foggy or discolored look on the window. In less severe cases the condensation appears as round splotches or in diagonal patterns and is most visible when the sun is low in the sky.
While regular maintenance and cleaning goes a long way in preventing a broken seal there is no real way to clean these surfaces. However if you need any such windows replaced we would love to recommend a great friend of ours.