· by Michael Blair, Nashville's Window Cleaning
Windows at the end of a build or a renovation carry things a normal clean never meets: manufacturer labels and their adhesive, silicone smears from the glazing, paint and stain overspray, mortar and concrete splash, drywall dust ground into the frames, and sometimes the mineral haze from a pressure wash of the brick. Each comes off differently, and the wrong approach to any of them scratches glass that was perfect a week earlier.
What is actually on the glass
Labels and the adhesive they leave behind. Silicone from the glazing bead, which smears rather than washes and is invisible until the light catches it. Latex or oil paint spatter and stain, on the glass and on the frame. Mortar, stucco and concrete splash, which are alkaline and start etching glass if left. Drywall and sanding dust in the tracks and on the sills. And, on new construction where the brick was acid washed, a possible acid haze on the glass below.
Most of that is not soil in the ordinary sense and will not respond to a squeegee and a solution. The routine window clean that follows a build is quick; the construction clean that precedes it is the job.
The scratching problem
Scraping construction debris off with a razor blade was standard practice for decades and it is where the argument starts. Some tempered glass carries fabricating debris fused to its surface during manufacture, tiny particles that a blade drags across the glass leaving fine scratches. Glass manufacturers and window cleaners have disagreed about responsibility for years, and the practical result is that many cleaners will not scrape tempered glass, or will only do so with a written waiver.
Low-E coatings on the inside face of newer glass are another concern. The coating is inside the sealed unit on most residential windows and cannot be touched, but on some products it is exposed, and abrasives or scrapers damage it. Ask what the glass is before anyone puts a blade to it.
- Identify tempered glass by the etched stamp in a corner
- No dry scraping, ever; wet the glass first if a blade is used at all
- Test any blade work in a corner and inspect in raking light
- Solvents for silicone and adhesive, not abrasion
How each residue comes off
Adhesive from labels responds to a citrus or mineral spirits based remover, dwell time, and a plastic scraper. Silicone smears come off with a silicone digester or, with patience, mineral spirits and a cloth; they do not come off with glass cleaner. Latex paint spatter softens with warm soapy water and lifts with a plastic blade; oil paint and stain need mineral spirits. Fine steel wool, the grade sold for glass, removes paint and stubborn film without scratching plain annealed glass, and it is the tool most professionals reach for before a blade.
Mortar and concrete splash need to come off soon after the work, while they are soft, with water and a plastic scraper. Once cured they are bonded and etching, and removal involves a mild acid cleaner that has to be kept off the frames and the surrounding masonry. This is the residue most worth catching early.
Frames, tracks and screens
The glass is the visible part. The tracks are where drywall dust, sawdust and mortar collect, and a window that is hard to slide a year after a build usually has cured debris in the track. Vacuum, then brush, then wipe, before any water is used, because wet drywall dust turns to paste. Vinyl and aluminum frames take mild detergent; solvents that clear the glass can dull or stain them.
Screens on a new build are often filthy from the construction site and are cleaned separately with a soft brush and detergent, then rinsed and dried before going back in. Do all of this before the routine glass clean, not after, or the next rain washes track debris across the glass you just finished.