Grooves in the glass

[Armistead Cleaning]

Today I cleaned the windows of a new build house. The windows had been cleaned about 5 months ago by a cleaning company after the house was completed, so it wasn't too bad today. But when I was cleaning the patio windows I noticed lots of grooves or channels. I've seen this before, but not as bad as it was today with this house. I just wondered what causes this?

 

[scottish cleaning service]

Sometimes its inside the glass unit and comes from the rollers moving the glass. The imprint stays inside the unit and needs to be replaced.