The glass is half the job. The frame is the other half, and the frame is the part you can ruin without realizing you ruined it until the next season. The four common substrates, what each one actually wants from a cleaner, and the protocol that separates a long-lived frame from one that needs replacement five years early.
The frame is where the long-term cost lives. Identify the substrate first, then match the protocol:
Identification first, every time. The damage from a substrate mismatch on a frame is rarely catastrophic in a single cleaning, but it accumulates across seasons in a way that shows up at year five or year seven and is not recoverable then.
I have been running a four-truck residential-and-commercial operation out of Falls Church, Virginia, since 2003. The Mid-Atlantic is one of the few markets in the United States where all four common window-frame substrates show up in routine rotation across a single working week — vinyl in the postwar suburbs, aluminum in the 1960s and 1970s commercial stock, wood in Old Town Alexandria and the Richmond Fan, and fiberglass-composite in the newer replacement installs that have run through the corridor since roughly 2010. A cleaner working a referral chain that pulls from McLean to Williamsburg to Loudoun across a single quarter is going to put their hands on every one of these substrates within a few weeks, and the protocol for each one is different in ways that matter.
The cleaning trade pays a lot of editorial attention to glass. It pays much less to the frame, and the result is that I see frame damage on every working week of every year that is recoverable for the homeowner only at the cost of full unit replacement. The damage is rarely from a single mistake. It is almost always from a substrate mismatch repeated across many cleaning cycles, where the cleaner — usually a homeowner, sometimes a professional who learned the trade on one substrate and never updated — has been using a chemistry that the frame slowly cannot survive.
This piece is the reference. The four substrates, what each one actually is, what it wants from a cleaner, and what it will not tolerate. Identify first; then clean.
Identify the substrate before you put a cleaner on it. If you cannot identify it, default to the gentlest protocol on this page (the wood-frame protocol) and work up from there.
This is the same rule the vinegar question and the ammonia piece put on the glass-side conversation, and the logic is the same. The damage from a substrate mismatch is cumulative across cleaning cycles, often invisible after the first contact, and not recoverable once it shows. The frame substrate is no different. The difference is that the frame failure modes are harder to spot in the first few years, so the homeowner does not realize the cleaning protocol is the problem until the damage is past recovery.
Two ways to identify a frame substrate without removing the window:
The tap test. Tap the frame firmly with a fingernail at a midspan point. Vinyl produces a dull, slightly soft thunk. Aluminum produces a clear, metallic ring. Wood produces a deeper, woodier thunk than vinyl, and the precise quality depends on the species and age. Fiberglass-composite produces something between vinyl and wood — a slightly harder thunk than vinyl, slightly less wood-warm than wood.
The seam test. Look at the corner joints of the frame. Vinyl frames have welded mitered corners — the seam is visible as a thin fused line. Aluminum frames have mechanically joined corners with a visible screw or staked joint. Wood frames have mortise-and-tenon or doweled corners, usually with a visible joint line and sometimes with a wood plug covering a screw. Fiberglass-composite frames have a mechanically joined corner that visually resembles aluminum but reads as a polymer at the seam edge under close inspection.
If the tap and seam tests have not given you a confident answer — or if the frame you are looking at has been painted over and you cannot read the seam clearly — the Frame Substrate Identifier walks the same decision tree above with a handful of additional questions about weight, temperature behavior, and age-of-construction, and returns the substrate plus the protocol it wants. The four substrate sections below are the long version of what the tool encodes.
Now the four substrates.
Vinyl is the most common modern residential frame substrate in the United States and has been the majority substrate in new-construction residential since roughly 2000. The polymer base is rigid polyvinyl chloride (PVC) with a UV-stabilizer package and a pigment system, typically titanium dioxide for white frames and assorted oxide pigments for colored frames.1
The good news about vinyl: it tolerates almost any cleaner that a homeowner is likely to have in the house. Dilute surfactant solution is fine. Vinegar at any reasonable concentration is fine — the acetic acid does not attack rigid PVC. Ammoniated cleaner is fine on the frame surface, though I do not recommend using it as the routine frame cleaner for the reasons covered in the ammonia piece on the glass side. Mild abrasives — a Magic Eraser, a non-scratch scrub pad — are fine for spot work, used with restraint.
The bad news: vinyl has three things it does not tolerate at all.
Solvents. Acetone, mineral spirits, lacquer thinner, and most commercial paint-prep solvents will attack the polymer surface, producing a localized softening and discoloration that is permanent. The damage shows immediately and does not recover. If you have a paint or adhesive spot on a vinyl frame, do not reach for the solvent kit. The right answer is mechanical removal with a plastic scraper and patience.
Bleach. Sodium hypochlorite at full residential strength produces a chalking effect on vinyl that is permanent and not recoverable. The same chemistry that bleaches a stained shirt fades the vinyl-frame pigment, and the chalk migrates to the surface as a powder. This is the failure mode I see most often on vinyl frames where the homeowner has been using a deck-cleaning protocol on the surrounding siding and getting bleach overspray on the windows.
Pressure washing at high PSI. Vinyl will deflect under high-pressure water in a way that opens up the weep slots and the sash-joint corners, driving water into cavities the frame is engineered to keep dry. The damage is mechanical rather than chemical, but the long-term effect is sash-joint failure and frame seal compromise. The right answer for a dirty vinyl frame is dilute surfactant solution and a soft brush, not the pressure washer.
The vinyl-frame failure mode that homeowners describe as "the windows are getting old" is almost never a cleaning-protocol problem. It is UV chalking and sash-joint deterioration at year ten to fifteen, both of which are scheduled-replacement issues rather than cleaning issues. A vinyl frame that has been cleaned with a reasonable protocol will not visibly age faster than one that has been left alone. The substrate is genuinely forgiving.
Aluminum frames were the dominant residential substrate from roughly 1965 through 1995 and remain the dominant commercial substrate in mid-rise office construction. The cleaning-relevant material is not bulk aluminum but the anodized oxide layer on the surface, which is a hardened aluminum-oxide coating formed by an electrolytic process during manufacture and which functions as the surface that all cleaning chemistry actually contacts.2
The anodized layer is thin (typically 10 to 25 microns), bonded to the substrate, and harder than ordinary surface oxide. It is also significantly more chemically reactive than the bulk aluminum below it. This is the property that determines the cleaning protocol.
Alkaline cleaners attack the anodized layer. Ammoniated cleaner, sodium-hydroxide-based degreasers, oven cleaner, and most heavy-duty alkaline household cleaners will, in repeated contact, etch through the anodized surface and expose the bulk aluminum beneath it. The exposed aluminum then begins normal atmospheric corrosion, producing the characteristic pitting that defines a failed aluminum frame. The damage is not recoverable; the frame must be replaced or, in some cases, re-anodized at substantial cost.
Acid cleaners also attack the anodized layer, by a different mechanism, and the damage pattern is similar. Vinegar at routine cleaning concentration is generally acceptable on intact anodized aluminum for incidental contact, but sustained acid cleaning is a failure path. Strong acids — CLR, sulfamic acid, hydrochloric — will produce immediate visible damage and must be kept off aluminum frames entirely.
The right protocol for aluminum frames is pH-neutral cleaning and a thorough rinse. Dilute surfactant solution (the House Standard recipe is fine, see the Solution Calculator), a soft cloth or brush, and a clean-water rinse to remove any cleaner residue. The rinse step matters more on aluminum than on any other frame substrate because cleaner residue that pools at sash corners and dries will, over many cycles, locally elevate the pH of the contact area and produce localized etching.
Coastal aluminum frames carry an additional protocol layer that overlaps with the salt spray piece — chloride aerosol accelerates the pitting failure mode by an order of magnitude, and the right answer for coastal aluminum is a fresh-water rinse on the frames at every cleaning cycle and a routine cycle interval shorter than what an inland route would use.
Painted aluminum frames — typically powder-coated rather than wet-painted — are more forgiving than bare anodized aluminum. The powder coat is a polymer surface that tolerates a wider chemistry range, similar to vinyl. But the coat is not infinitely durable, and once it has been compromised at any point — a scratch, a chip, a deteriorated edge — the underlying anodized layer takes over the chemistry conversation and the alkaline-and-acid rules apply again.
Wood is the frame substrate the cleaning industry handles worst, and it is the one I see ruined most often by well-intentioned homeowners who have been told that a wood frame "just needs the same cleaning as the rest of the trim." It does not. The wood frame is a structural-and-finish substrate that responds to cleaning chemistry through whatever finish it is currently carrying — paint, shellac, varnish, polyurethane, oil — and the right cleaning protocol depends on identifying the finish before the substrate.
The dry-side rule. For routine cleaning of any wood frame in any finish, the first move is dry-side: a soft brush or a dry microfiber to lift dust, pollen, and surface debris from the sash, sill, and corner joints. This is the largest single removable category of contamination on a wood frame, and dry-side handling produces zero substrate stress. I do most of the wood-frame cleaning on my route on the dry side and only escalate to water-side work when there is a specific contamination problem to address.
The water-side protocol when needed. When water-side cleaning is necessary, the protocol is: damp microfiber (not soaking wet) with dilute surfactant solution, single-pass wipe-down, immediate dry-cloth pass behind it. The cloth should be damp enough to lift contamination, not wet enough to leave moisture sitting on the wood. Standing moisture on a wood frame is the failure mode that produces edge rot at year ten and joint failure at year fifteen.
What never goes on a wood frame:
The pre-1978 lead-paint rule. Any wood frame in a building constructed before 1978 may carry lead-based paint, and any cleaning protocol that involves abrasion, sanding, or aggressive solvent contact on such a frame falls under the EPA Renovation, Repair and Painting (RRP) rule.3 This is a federal regulation with enforcement teeth, not a best-practices guideline. The practical effect for a homeowner or a routine residential cleaner is: gentle dry-side cleaning only, water-side limited to a damp microfiber, no abrasion, no scraping, no aggressive solvent. Deeper restoration work — paint removal, frame repair, sash rebuilding — goes to an RRP-certified contractor.
Heritage wood frames — anything pre-1940, particularly the leaded-and-mullioned and Federal-period stock that runs through Old Town Alexandria, the Richmond Fan, the historic Annapolis neighborhoods, and across the broader Mid-Atlantic heritage corridor — pair with the historic glass piece on the substrate-and-conservation side. The cleaning protocol on a heritage wood frame should be even gentler than the standard wood protocol: dry-side only as the default, water-side only with conservator review.
Fiberglass-composite is the newest of the four substrates in residential rotation and the one most under-documented in the consumer-facing literature. It has been the highest-growth-rate replacement-window substrate in the Mid-Atlantic market for roughly the last decade, and on a 2026 working route it now shows up on a meaningful fraction of post-2015 replacement installs.
The substrate is pultruded fiberglass — continuous glass-fiber strands drawn through a resin bath and cured into a structural profile.4 The visible surface is a gel-coated polymer layer that protects the underlying composite from UV exposure and provides the cleaning-relevant chemistry surface. The gel coat is harder than the painted surface of an aluminum frame but softer than the anodized layer; it tolerates a wider chemistry range than wood or aluminum but has specific failure modes.
What fiberglass-composite tolerates:
What fiberglass-composite does not tolerate:
The fiberglass-composite frame is a younger substrate in the long-term-durability literature than vinyl or aluminum, and the failure modes at year twenty and beyond are still being characterized. The manufacturers' care guides — Marvin's Ultrex documentation, Andersen's composite-product guide — converge on a conservative cleaning protocol that is broadly similar to the protocol I have laid out here.
When I am working through a route and pulling up to a house I have not been to before, the sequence I run is the same every time:
The protocols themselves are not difficult. The discipline of identifying first, before opening the bottle, is the part that separates a cleaner whose customers' frames look good at year ten from one whose customers are calling about premature replacement at year seven. The frame is half the job. The protocol that respects the substrate is the rest of it.
The dry-side and wet-side techniques the four protocols above call for are documented in the Technique Library — the soft-brush dry pass on aluminum, the damp-microfiber-only routine on painted wood, the rinse-step discipline on coastal anodized aluminum, and the gel-coat-aware approach for fiberglass-composite. The library is the technique-level reference the substrate-level rules above route to.
Tony Petruzzi runs a four-truck residential-and-commercial window-cleaning operation out of Falls Church, Virginia, with a working book that covers the DC-Virginia-Maryland metro and reaches into the Tidewater and the Blue Ridge on referral. He came to the trade in 2003 after three years in commercial property maintenance.
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Polyvinyl chloride (PVC) is the polymer base for modern vinyl window frames. The frame extrusion is typically rigid PVC with a UV-stabilizer package and a titanium-dioxide pigment system. The chalking failure mode at year ten to fifteen is the gradual depletion of the UV-stabilizer package as it absorbs cumulative sun exposure; the chalk is the unprotected pigment migrating to the surface. The replacement decision is structural rather than cosmetic — a chalking frame is signaling that its UV protection has run out, and the polymer underneath is degrading. ↩
Anodized aluminum has a thin (typically 10–25 micron) aluminum oxide layer formed by an electrolytic process. The oxide layer is structurally bonded to the aluminum substrate and is harder than ordinary surface oxide. It is also chemically more reactive than the bulk aluminum below it — both alkaline and strong acid cleaners will attack the oxide before they attack the metal. Once the oxide is locally compromised, the bulk aluminum beneath it begins normal corrosion in atmospheric exposure, producing the pitting that defines aluminum-frame degradation. ↩
Pre-1978 painted wood frames may carry lead-based paint. Any cleaning protocol that involves abrasion, sanding, or aggressive solvent contact on a pre-1978 painted wood frame must follow EPA Renovation, Repair and Painting (RRP) rule procedures. This is not a cleaning-best-practices recommendation; it is a federal regulation with enforcement teeth. The right answer for any pre-1978 wood frame is gentle dry-side cleaning only, with water-side work restricted to a damp microfiber, and any deeper restoration work referred to an RRP-certified contractor. ↩
Pultruded fiberglass is the manufacturing process by which continuous glass-fiber strands are drawn through a heated resin bath and cured into a structural profile. The resulting composite has a thermal expansion coefficient close to glass itself, which is why fiberglass frames sit more stably against the glazing across seasonal temperature swings than aluminum (much higher expansion) or vinyl (different swing pattern). The cleaning-relevant property is that the resin surface is gel-coated rather than painted, and the gel coat is what protects the underlying composite from UV. Aggressive pressure-washing or solvent contact strips the gel coat first. ↩
Tony runs a four-truck residential and commercial window-cleaning operation out of Falls Church, Virginia, covering the DC-Virginia-Maryland metro and the broader Mid-Atlantic. He came to the trade in 2003 after three years in commercial property maintenance, and has been on the same Falls Church base since.