Colour Stability in uPVC Windows and Doors Explained

1. Every year I visit homes that are ten, fifteen, even twenty years into their window journey. Some frames look almost new, others are blotchy or tired. The difference is rarely down to how often they are wiped, and almost never about the age alone. It comes down to material chemistry, pigments, extrusions, and how the frames were specified. Colour stability is not glamourous, yet it decides how your uPVC windows and doors will look when the novelty wears off and the weather has had its say. This is a practical guide drawn from the field. It is written for homeowners weighing up options, installers who want fewer call-backs, and anyone comparing upvc windows and doors with aluminium windows and doors in the Go to the website showroom light. I will cover what affects colour stability, how to read specifications that actually matter, and what maintenance is worth your time. What “colour stability” really means Colour stability is the frame’s ability to resist visible change under sunlight, heat, moisture, and cleaning. There are two pieces to it. First, the inherent fade of the pigment system. Second, surface changes that alter how light reflects, such as gloss loss and micro-chalking. When a white uPVC frame goes slightly creamy or develops a dull patch, that is colour and surface interacting. On a grey or black foil, you notice patchiness or a slight shift in shade. With woodgrains, the eye picks up uneven gloss more than hue shift. In the lab, colour change is measured with a spectrophotometer and expressed as delta E. In the real world, people judge with their living room eyes. After a decade, a delta E of 3 may be a non-issue on white in North Yorkshire, yet obvious on a south-facing, anthracite coastal install where salt and sun conspire. The number matters, but viewing conditions and expectations matter more. What uPVC is made of and why it matters uPVC is unplasticised polyvinyl chloride, which means it is rigid without added plasticisers. The frame profile is extruded from a PVC compound that includes stabilisers, impact modifiers, pigments, and sometimes titanium dioxide (TiO2) for whitening and UV protection. The balance of these ingredients sets the baseline for colour stability. Most reputable extruders use heat stabilisers based on calcium-zinc systems rather than older lead-based additives. Calcium-zinc gives good colour hold and is the standard across the UK and EU. The TiO2 content and grade are critical too. Rutile TiO2 with a suitable surface treatment helps scatter UV and prevent degradation deeper into the profile. I have seen budget profiles with lower TiO2 levels, fine in the showroom, but they chalk faster outdoors and get that powdery wipe-off after strong summers. For coloured finishes, two paths dominate. Either the base uPVC is co-extruded with an acrylic capstock pigmented to colour, or a laminated foil is bonded to the uPVC. Each system has strengths. Acrylic caps can be extremely durable in lighter colours and resist edge peeling. Laminated foils offer more textures, including woodgrains and metallic looks, and modern foils are surprisingly tough when sourced from a top-tier supplier.

2. Sunlight, heat, and exposure: what actually happens UV radiation breaks bonds in polymers and can degrade pigments. Modern uPVC compounds include UV absorbers and stabilisers to slow this. In practice, the first things you notice are gloss changes and subtle shifts in the lightness of the surface. Whites can go slightly warmer if the compound has a touch of cream tone to start with. Deeper colours can lighten or dull. Prolonged heat accelerates reactions, and dark colours get hotter, so roofline-adjacent frames or bay windows can run 20 to 30 degrees warmer than ambient on a July afternoon. On a thermal camera, I have measured anthracite foils approaching 65 to 70°C in full sun. That heat tests the bond between foil and substrate, as well as the tolerance of seals and gaskets. Coastal exposure is its own game. Salt on the surface attracts moisture, and the wet-dry cycle speeds wear. Frames near busy roads pick up soot and fine particulates that abrade the top layer when wiped. None of this means uPVC is fragile, but it does mean maintenance and specification need to match the environment. White, coloured, and woodgrain: differences you can see White uPVC has a reputation for holding up well. On good profiles, a decade will show only a slight flattening of gloss and minimal yellowing, often not noticeable unless you put a brand-new offcut alongside. Problems arise with economy- grade compounds, lower TiO2, or aggressive cleaners used year after year. If you want pristine white twenty years on, choose a profile brand with published outdoor weathering data and ask what delta E value they warrant over time. Solid colours co-extruded into an acrylic cap do well for lighter greys and creams. Darker caps are available, but heat build-up increases movement and can stress edges at corner welds. Laminated foils offer the popular anthracite and black looks. The top-performing foils come with UV-inhibiting layers and have passed thousands of hours in accelerated weathering and natural desert exposure. You will still see a slow softening of gloss on the sunniest elevations. Good foils avoid the patchy “tiger-striping” that cheaper ones develop as the grain emboss wears. Woodgrain foils behave like coloured foils, but the grain helps hide minor scuffs and dust. Where they can be sensitive is at mitres and beads if the lamination and trimming are careless. I have stood back from an otherwise tidy install where a hairline of white showed at the bead edge because the foil coverage was too tight. From a distance, that tiny mismatch reads as discolouration. Properly trimmed beads and colour-matched gaskets tidy the look and preserve the illusion of timber. How aluminium compares, and where double glazing suppliers fit When homeowners compare upvc windows and doors to aluminium windows and doors, colour stability is one of the decisive factors. Powder-coated aluminium in marine-grade finishes has excellent fade resistance, especially with PVDF systems. Polyester powder coat in standard architectural grades holds up well in milder climates, with a gradual mattification over 10 to 15 years. For very dark colours in full sun, aluminium’s thermal expansion is lower than uPVC, so coatings see less flex. That said, modern uPVC foils have closed much of the gap for most UK sites.

3. Double glazing suppliers sit at the junction between extruders, lamination houses, and installers. The best suppliers curate profile systems and foil partners with proven track records, not just the cheapest price that week. Ask your supplier two questions that separate marketing from substance. First, what natural exposure testing backs this finish, and where? Second, how do they handle repairs for scuffs or film damage during installation? I keep a small kit of manufacturer- approved cleaner, touch-up pens, and corner-guard replacements because prevention beats aftercare. The role of glass and gaskets in perceived colour change People often blame the frame when the eye sees the whole aperture. Glass specification affects how intense the frame appears from indoors. With high-performance coatings, the visible light transmittance can sit in the mid-60 percent range. That tints the interior perception, especially on grey frames, making them look flatter than the exterior view. Argon-filled double glazing does not change frame colour, but the reflections can highlight or soften differences between sash and outer frame if one surface has aged differently. Gaskets and trims frame the colour. EPDM gaskets in deep black stay stable for years. TPE gaskets can grey faster. A faded gasket next to a stable frame looks like a fading frame from three steps back. When replacing beads or gaskets, match material type and colour so the visual balance remains constant. What to ask for before you sign A short checklist helps cut through marketing. Keep it simple and specific. Pigment and foil provenance: confirm the foil or capstock brand, the UV class, and whether it carries a published outdoor weathering record, not only lab hours. Delta E targets: ask for the expected colour change over 10 years on a south-facing elevation in the UK or your region. Heat management: confirm adhesion class for laminates and any special guidance for dark colours on large spans or bi-folds. Cleaning and warranty terms: get the permitted cleaning agents in writing and the conditions that protect the colour warranty. Bead, gasket, and accessory matching: ensure all visible components share the same colour stability rating. Most reputable suppliers will welcome these questions. If you get vague answers or a push toward “everything is the same,” treat it as a warning. Installation details that affect colour stability I have seen frames fade unevenly because of errors that had nothing to do with the material. Poorly sealed end-grains on trims wick water and stay damp, accelerating microbe growth that stains the surface. Mastic smeared onto foils and left to cure can etch a faint gloss difference that reads as a pale halo after a season. On white uPVC, aggressive brick acid splashes leave a permanent matte patch that looks like discolouration. Edge temperatures matter most on dark colours. Bi-fold doors with wide spans and black foils work, but you want controlled expansion. Use recommended packers and avoid over-tight anchoring that concentrates stress at corners. A slightly oversized gap with the correct compressible foam and backer rod allows the frame to move without creasing beads or opening tiny edges where UV can creep under a foil. How cleaning choices show up years later Colour stability and cleaning have a quiet partnership. If you stick to mild, pH-neutral cleaners and a soft cloth, you keep the top layer intact. Micro-abrasives remove dirt and a little surface each time. Do that monthly for years, and you get a slow mattification that people mistake for fading. Solvent wipes remove tar or sealant, but they can swell or dull foils if not immediately neutralised. On a service call I watched a well-meaning caretaker use neat acetone on a stubborn mark; the foil lost its sheen in a palm-sized patch within seconds. A routine that works in most settings: lukewarm water with a drop of mild detergent, soft sponge, gentle rinse, microfiber dry. Twice a year is enough for sheltered elevations, quarterly for exposed coastal or roadside sites. For sap or tar, use the manufacturer’s recommended cleaner, not a general-purpose solvent. If you are in doubt, test on an offcut or an inconspicuous back edge. What warranties really cover

4. Colour warranties vary. A ten-year frame warranty may only cover structural integrity and hardware, not colour. When colour is covered, the wording usually promises that visible fading will remain within an agreed delta E under normal conditions. Normal is defined by distance from the sea, altitude, and maintenance frequency. For coastal homes, some suppliers require six-monthly fresh-water rinses to keep the warranty. Keep a simple log, even just dates on a calendar app. If you ever need a claim, those notes help. Make sure repairs are practical. If a sash must be replaced to address a colour issue, can the supplier colour-match to the weathered outer frame? Some systems allow swapping a sash without disturbing the outer frame, which avoids the “new next to old” look. On foiled products, it is often better to replace paired elements on the same elevation to avoid a near- match that looks off for years. The long view: 5, 10, and 20 years At five years, good white uPVC should look fresh with only a slight reduction in gloss on the sunniest side. Coloured foils should be even, with seals and beads as dark as day one. Any patchiness at this stage usually points to chemical exposure or abrasive cleaning, not the material. At ten years, small differences between elevations appear. The south and west faces will read a touch flatter than north and east. Dark greys will have softened their sheen. Any differential between sash and outer frame is often tied to the microclimates of recesses and reveals. Switch out tired gaskets, give a careful clean, and the overall impression snaps back. At twenty years, expect an honest patina. Whites can show a gentle warm tone, not yellow, just less clinical than new. Foils still present nicely if they started with quality, though edges and high-touch points like patio door handles may show a touch of polish from hands and cleaning. If a home is being refreshed with new render or roof, this is the moment to judge whether replacing the most exposed elevation brings harmony. It often does. When aluminium is the better choice There are projects where aluminium windows and doors have the edge for colour stability. Dark, expansive glazing on a south-facing coastal property leans toward marine-grade aluminium with a high-quality powder coat or PVDF. The rigid frame holds tolerances under heat, and the finish resists harsh environments with minimal gloss change. If you love the slim sightlines anyway, the colour benefit is a bonus. For cottages and period semis inland, upvc windows and doors give a softer look and excellent thermal performance, and modern foils hold their colour well enough that the difference is academic. The comparison is not a binary “better or worse” but matching material to site, colour, and expectations. I keep both options in the bag for clients because the right answer shifts with context. The science behind the marketing claims You will see numbers like 6,000 or 10,000 hours of accelerated weathering in brochures. The machines here are usually QUV systems with UVA-340 lamps that simulate sunlight and condensation cycles. These tests are useful for screening, but they are not a one-to-one map to years outdoors. Natural weathering tests, like Florida or Arizona exposures, give better clues. A profile or foil that has 2 to 3 years of natural desert exposure with acceptable delta E results is a strong indicator discover new window trends for UK performance, which is generally less punishing in UV but more variable in moisture. Another useful spec is heat build-up data for dark colours on standard substrates. If a supplier can show surface temperature curves for anthracite on a typical south-facing day, you can plan expansion gaps and fixings accordingly. Installers who get this right have fewer squeaks, creaks, or corner stresses that can later manifest as micro-cracks or lifted edges, which then invite UV in and accelerate colour shift. Practical tips that make a visible difference Colour stability is a long game, but a few habits compound nicely. Rinse salt and dust before you wipe, especially on foils. Dry grit is sandpaper in disguise. Shield frames during brick cleaning. If acid must be used nearby, protect with film and rinse generously afterward. Avoid dark foil on tightly enclosed, unventilated suntraps unless the system and glass spec are designed for it. Trapped heat is hard on

5. bonds. Keep plant pots a few centimetres off sills. Constant damp under a pot grows algae and leaves a dark halo the sun can etch into memory. Replace tired gaskets and scuffed beads. Small refreshes keep the overall look crisp and prevent misreading them as faded frames. None of these cost much. Put them together and your windows and doors keep their colour story neat. What I watch for during site surveys When I assess existing frames, I walk the elevations with the sun behind me, then with the sun across the surface, because sheen changes show differently. I check the junctions: sill end caps, mitres, and bead lines. If there is a difference between sash and outer frame colour, I ask about cleaning products and note rain shadow patterns. On foils, I run a finger along the leading edge at the rebate. A smooth edge means the laminate is bonded fully; a sharp or lifted feel suggests future trouble, especially on dark colours. I also look at the surrounding materials. Fresh render brightens everything and can make older frames look more aged by contrast. New fascia boards do the same. If a client is renovating in phases, I advise replacing or refurbishing frames before the final coats go on walls. That way, the eye calibrates to the new palette with the frames included. The installer’s toolkit for colour care Good installers carry a small set of care products specific to the frame system. I keep neutral pH cleaner, approved solvent wipes for spot use, a soft-bristle brush for gasket grooves, and microfibre cloths that do not shed. For foils, I carry touch-up pens matched to anthracite and black because tiny scuffs happen on sites with scaffolding and heavy boots. The trick is to fix small issues before handover, not after the client has watched a mark for six months. I also remind clients, gently, to avoid pressure washers aimed at the beads. A concentrated jet can drive water past seals and lift edges over time. A garden hose with a spray head, held at an angle, cleans safely. Choosing a supplier who values colour as much as you do Among double glazing suppliers, the ones who care about colour stability do small things right. They store foiled profiles away from direct sun, not on the highest racking under skylights. They rotate stock so older batches are used first, and they document batch numbers so a future replacement sash can be matched. They train fitters to handle frames with padded carriers rather than by the bare foil edge. They specify glazing packers that do not leach plasticisers, which can stain over years. When you are comparing quotes for upvc windows and doors, do not just look at U-values and hardware options. Ask to see a five-year-old installation the supplier completed, ideally on a sunny elevation. Nothing beats seeing with your own eyes how the colour holds up. If they happily arrange a visit, you are likely in good hands. Final thoughts from the field

6. Colour stability is not luck, and it is not guesswork. It is the sum of the compound and foil chemistry, the honesty of the specification, the care taken during installation, and modest maintenance over time. White uPVC remains a solid choice, forgiving and tidy for decades when sourced well. Coloured and woodgrain foils have matured to the point that most homeowners can choose them confidently, especially from trusted systems with real weathering data. Aluminium delivers stellar stability on the harshest sites and for the deepest, darkest hues, with the bonus of slim sightlines. If you plan with the sun in mind, choose finishes with proof rather than promises, and treat the frames with a light touch, your windows and doors will look like themselves for years. That is the quiet victory of colour stability. It is not dramatic. It is what you do not notice when you walk up the path, quarter of a century in, and the frames simply belong. Doorwins Address: Office 11, Dearden House, W Gate, London W5 1BS Phone: 020 8629 1250 Our specialists at Doorwins are one of the number one windows and doors specialists in London. Our in-house fabrication team specialise in manufacturing and installing premium aluminium windows for modern homes and luxury developments. The work we carry out at Doorwins demonstrates strong craftsmanship, product knowledge and reliability. Whether you need secure composite front doors, we’ll recommend and install the perfect system. As a reputable double glazing supplier in London, Doorwins continues to set benchmarks for quality, reliability and service. AREAS COVERED: North London, West London, South London, East London, Central London, Inner London. Doorwins windows and doors Address: 4 Observatory Gardens, London W8 7HY Phone: 020 8629 1171

7. Description: London specialists in aluminium and uPVC double glazing for homeowners seeking long-life frames, crisp sightlines and energy savings. Services: Survey → design → fabrication → supply and fit with dedicated project coordination. Products: Complete window and door sets for whole-house replacements, matching finishes and hardware, plus complementary roof lighting options.