Can tinted windows be cleaned?

The word covers three different things, and each one gets its own line before any rule.

• Tinted glass. The pane itself is tinted: the National Glass Association (NGA) writes that architectural glass “can be clear or tinted.”
• A reflective coating. NGA says reflective coatings increase the reflectivity of the glass and “are normally obvious,” and that some may sit on the exposed surface.
• An applied film. A film applied to the surface of the glass. NGA notes that exposed films, security or spall films for example, may be applied to the inside surface of the glass.

A fourth layer can hide behind all three. Low-E coatings, NGA writes, are typically neutral in color and “very difficult to see,” so a window that looks plain may still carry one; where that coating sits is the subject of whether Low-E windows need special cleaning.

NGA's own first step is the same sorting: “Before proceeding with cleaning, determine whether the glass is clear, tinted or reflective.” Whether a pane is tinted glass, coated or filmed is the window maker's or the film supplier's to confirm. How those kinds of glass sit beside impact and tempered panes is set out under impact, Low-E, tinted and tempered glass types.

The rule NGA attaches to tinted and reflective glass is about heat: cleaning either in direct sunlight should be avoided, because the surface temperature “may be too hot for optimum cleaning.” Timing a clean around the sun is covered in the window cleaning questions on cleaning in the middle of the day, and summer as a season for glass under whether windows can be cleaned in the summer sun.

A reflective coating adds a second rule when it faces outward. NGA writes that “Surface damage is more noticeable on reflective glass as compared with the other glass products,” and that where the reflective surface is exposed, special care must be taken, because damage to it may remove coating and cause a visible change in light transmittance. NGA's paper also says razor blades should never be used on coated glass surfaces.

NGA publishes a pencil test for locating a reflective coating, and scopes it to that coating alone; it is set out under how the industry finds where a coating sits. NGA does not offer it as a way to find Low-E or film.

Film changes the tools. For glass with film applied, NGA's paper asks that the film not be scratched: bristle brushes and abrasive cleaning materials are out, a soft cloth or clean synthetic sponge is recommended for washing, paper towels and newspapers are not, and neither is rubbing vigorously or pressing hard.

It changes the solution too, without a flat ban. NGA recommends mild detergent or household window cleaning solutions for window films. Ammonia is the one it hedges: solutions containing it “may not be suitable for all film types,” and the film supplier is the one to ask for recommended cleaners. Where film has been spliced, NGA says to clean in the direction of the splice.

The International Window Film Association (IWFA) names a soft cloth or squeegee for drying a filmed window. Whatever the tool, residue is the thing to avoid: the PGT, CGI and WinDoor instructions, for their own products' glass, say to rinse and dry any run-down quickly so a cleaner leaves no residue on the glass, and solution left to dry on a pane is what shows as streaking.

What else can harm a film, how long a new film's adhesive takes to cure and what its warranty covers are taken up under whether window film can be damaged by cleaning.

Put the three rules side by side and the order of work follows from them. The sun rule applies to tinted and reflective glass. The special-care rule applies where a reflective coating is exposed. The brush, abrasive and ammonia rules apply where film has been applied. None of them can be chosen until someone knows which kind of tint is on the pane.

Two more checks from NGA's procedure apply to all three. One is a test area on one window, examined for damage to the glass or any exposed coating before the project goes on, which belongs to whether window cleaning can scratch the glass. The other is a wind check, taken up under whether windows can be cleaned when it is windy.