What is the brown discolouration in the spacer between the panes of glass in double glazing units

Hi, unfortunatly, any discolouration inside a unit means the seal has broken down. This can be caused by either age, frost , poor manufacture or fitting. The only solution is replacing the affected unit. However, if one unit has failed,its worth checking the others, as its lightly others will have gone too Cheers Terry

Hello. Brown is an unusual colour unless they are fitted into a stained wooden window either way the unit has failed and needs replacement. Hope this helps

The brown stain in the unit is most likely a coating burn. Its usually a slightly irabge/ brownie colour. Its a defect that can occur when the glass is low e coated. Unfortunately if its not visible from 3m distance at 90 degrees to the glass ss you look through it ( and not directly at it) its considered acceptable due to manufacturing tollerances/ visual impairments.