Streaking

A streak starts when solution stays on the glass. NGA's wash method, set out on the service page as the published exterior cleaning method, soaks the glass with clean water and a mild, non-abrasive cleaning solution, and then, immediately following the application, a window cleaning squeegee removes all of the cleaning solution from the glass surface. NGA does not name streaks in that step, but its timing leaves no solution behind to dry into one.

PGT, CGI and WinDoor reach the same point in their homeowner care instructions from the rinse side, telling owners to rinse the glass thoroughly with clean water to prevent the cleaning solution from leaving a film on the glass. Both instructions end in the same place: no solution left on the pane to dry.

The same guide adds a second instruction: rinse and dry any run-down quickly to prevent the cleaning solution from leaving a residue on the glass. Run-down is the solution or water that keeps running down the pane after the main wash.

The maker names residue, not streaks, but the logic matches the squeegee step: liquid left to dry where it ran leaves what it carried along that path.

Spotting is the neighboring mark: a spot is what water leaves after it evaporates where it sat, while a streak is solution or rinse water not fully removed. NGA names both in one sentence, for its pure-water technique, where the rinse is generally allowed to evaporate and the water must carry 20 parts per million of total dissolved solids or less to prevent spotting and streaking.

The tool behind NGA's wash step is its own entry at squeegee, and whether that tool or a cloth suits a given window is answered at squeegee versus cloth. Whether clean glass does anything for a business is a separate question, at whether window cleaning helps a storefront, and why marks on glass can show more when the sun is low is answered at why windows look dirty when the sun is low.