Josko Fenster und Türen has been manufacturing windows and doors in Kopfing, Upper Austria since 1960. The company name comes from its founder, JOhann Scheuringer KOpfing. Josko has been the market leader for wood/aluminium windows in Austria for almost 25 years, with seven Red Dot Design Awards and seven German Design Awards. Its vision: "We create joy and value for your unique home."
With 25 years in professional glass care, I regularly clean Josko windows across Vienna. Josko's flush design (flächenbündig), concealed hardware (verdeckte Beschläge), and combination of interior wood with exterior aluminium each require a specific approach that goes beyond standard window cleaning.
This guide combines two things: the care instructions from Josko's own Servicepass and product guides, and the professional glass-cleaning technique I've developed over 25 years of cleaning premium architectural windows. The manufacturer's guidelines are direct from the source, and the cleaning method is based on hands-on experience with these specific products.
What Makes Josko Windows Different to Clean
Josko produces three main window systems, and each one presents a different cleaning scenario.
Wood/aluminium windows (Platin, Amber) feature natural wood on the interior and a protective aluminium shell on the exterior. The wood side requires gentle cleaning products and cotton cloths. The aluminium side requires documented cleaning to maintain the warranty. Two different surfaces, two different methods, on the same window.
uPVC/aluminium windows (Safir) combine a durable uPVC interior with the same aluminium exterior. The interior is more forgiving than wood, but the aluminium warranty conditions still apply.
Aluminium windows (ONE) use aluminium throughout. Josko's ONE system features a frame width of only 5 cm on all four sides, creating a slim, symmetrical profile. The narrow frame means more glass, which makes proper glass-cleaning technique even more important.
Across all three systems, Josko pioneered concealed hardware (verdeckte Beschläge) in Austria in the early 1990s. The hardware is hidden within the frame, which creates clean sightlines but also means that the lubrication points are less visible and easier to overlook during maintenance.
Before we get into Josko's specific care requirements, it helps to master the foundational glass-cleaning technique that applies to all window types.
The Foundation: Professional Glass-Cleaning Technique
Glass is the job. Regardless of the frame material, the glass-cleaning technique is the same. If you can clean glass properly, the rest is maintenance. If you skip the technique, no amount of frame care will make the window look right.
The Window Cleaning Manifesto covers the foundation: essential tools, soap-water preparation, and the basic squeegee turns (top-to-bottom, side-to-side, and mixing these two together on large windows). It is free and takes five minutes to review, making it a smart starting point before cleaning any premium window.
Step by step, you will see how to achieve professional results at home, drawing on all the principles discussed below.
What Josko Recommends: Care Instructions from the Servicepass
Josko provides every customer with a Servicepass, a detailed care and maintenance manual covering glass, frame surfaces, hardware, and seals. The Servicepass is available as a downloadable PDF and is updated regularly. The current version is 2025/07.
Here are Josko's key care recommendations, presented directly from the Servicepass and product guides:
- Use only mild cleaning products such as heavily diluted washing-up liquid and soapy water (Seifenlaugen).
- Never use abrasive, corrosive, or solvent-based cleaning products.
- Use only soft cleaning cloths (weiche Putztücher) to avoid scratching surfaces.
- Do not use high-pressure or steam-cleaning equipment on windows.
- For wood surfaces: use mild cleaning products only. Interior wood surfaces require no additional care beyond this cleaning.
- For aluminium surfaces: eloxierte (anodised) and pulverbeschichtete (powder-coated) surfaces must be cleaned and maintained regularly to preserve the decorative appearance, especially in environments exposed to smoke, exhaust fumes, and aggressive airborne dust.
- For specialist aluminium cleaning and conservation of heavily soiled or chalked surfaces, Josko recommends the Innotec Service Set 4.
- When using professional cleaning companies, the GRM (Güterichtlinien für die Fassadenreinigung) guidelines must be followed.
These guidelines are the manufacturer's standard. What I add as a professional is the specific technique for applying these principles to achieve streak-free, crystal-clear glass on Josko's large-format windows.
Why Josko's Aluminium Warranty Depends on Your Cleaning Records
This is the detail that most Josko owners miss, and it is the most important section in this guide.
Josko's aluminium surface warranty covers protection against unnatural colour change and cracking on powder-coated and anodised aluminium profiles. But the warranty comes with a condition that Josko states clearly on its guarantee page: the warranty applies to aluminium profiles that have been demonstrably (nachweislich) cleaned at least twice yearly with approved cleaning products as specified in the Servicepass. Written cleaning and care documentation (schriftliche Reinigungs- und Pflegedokumentation) is required. The cleaning product used must be documented by presenting the purchase receipt (Vorlage der Rechnung).
In plain terms: if you cannot prove that you cleaned the aluminium surfaces at least twice per year with the correct products, and if you cannot show the receipt for those products, the aluminium surface warranty may not apply.
The warranty also excludes corrosion caused by environmental factors such as installation near the sea (salt air), roads with salt spreading, or areas with heavy industrial pollution.
What this means for you as a Josko owner: keep a cleaning log. Note the date, the cleaning product used, and save the receipt. This is not optional maintenance. It is a warranty requirement.
Professional Glass-Cleaning Technique for Josko Windows
Preparation
Fill a bucket with water and add a few drops of pH-neutral soap. This is the same solution professionals use across all premium glass. Josko's own recommendation of heavily diluted washing-up liquid aligns with this approach. The key is to keep the concentration low. Too much soap creates residue on the glass. Too little and the dirt will not dissolve properly.
Agitation: The Step Most People Skip
Dip your T-bar applicator (a T-shaped handle with a horizontal bar covered in microfiber fabric, designed for washing glass) into the soap water. Wet both sides of the microfiber cover. Apply the solution to the glass using overlapping strokes. This is agitation: you are loosening dirt, dissolving fingerprints, oils, and environmental deposits so that the built-up dirt has dissolved into the soap water and is ready for the squeegee to shave away.
If the dirt is not fully dissolved and released from the glass, the remaining dirt still stuck will be transported under the squeegee rubber, leaving smudges or smears. This is why agitation matters more than the squeegee itself.
On Josko's flush-design windows, agitation is straightforward. The flat frame profile means the T-bar applicator glides across the glass without catching on stepped frame edges. This is one of the practical cleaning advantages of Josko's flächenbündig design.
Detail the Frame Before Squeegeeing
Before you pick up the squeegee (a flat tool with a rubber blade for wiping off water), use a damp 100% cotton towelling rag to wipe the frame edges where glass meets frame. This removes the dust and dirt buildup that the squeegee cannot reach. If you skip this step, dirt from the frame edge will run onto the clean glass during squeegeeing.
On Josko wood/aluminium windows, be careful with the soap water near the wood interior surfaces. Wipe any soap water that contacts wood frames promptly. Josko specifies cotton cloths (weiche Putztücher). For wood surfaces specifically, microfiber is not recommended as it can mark the finish.
The Squeegee
You need the squeegee rubber to make the initial contact with the glass on a dry section (this is called cutting in). Place the rubber blade against the glass at a slight angle, roughly 45 degrees, and draw across the window in a controlled pass.
Three squeegee turns form the foundation of professional window cleaning:
Side to side: horizontal passes across the window. Tilt the squeegee at a slight angle to direct the water spillover to one side of the channel only.
Top to bottom: vertical passes down the window. Same tilt principle. Water directed to the lower side.
Turn with a twist (the "J" tune): the professional continuous motion. One smooth movement from top to bottom, linking turns with a wrist twist at each end. This is the technique that separates clean windows from crystal-clear ones.
For Josko's ONE aluminium windows with their slim 5 cm frame width, the squeegee can run closer to the edge of the glass. The narrow frame profile gives you more working space on the glass itself.
For windows beyond arm's reach, attach the squeegee to an extension pole. Keep the pole angle at roughly 45 degrees to the glass. Josko's larger fixed glazing units (Fixverglasungen) often require pole work.
Finishing: Edge Detailing
Clean away any excess soap water using your finger pressed into a 100% cotton towelling rag. Work into the edge where the glass meets the frame and remove any pooled soap water. Rotate the rag so you are only touching the glass with a clean section. Replace the rag with a fresh one every few windows to maintain a high-quality detail.
The squeegee turn determines how much detailing you need to do afterwards. A clean, confident turn with good rubber pressure and consistent overlap means less detailing. A hesitant or uneven turn means more.
Wood Surface Care
Josko's interior wood surfaces come in spruce, oak, wild oak, larch, and walnut, all sourced from sustainable Central European forests. Each species has a slightly different grain and finish, but the cleaning approach is the same.
Clean wood surfaces with mild cleaning products only. Josko specifies heavily diluted washing-up liquid or soapy water. Use soft cotton cloths. Do not use microfiber on wood, as it can leave marks on the surface. Do not allow water to pool on wood. Wipe dry promptly after cleaning.
Interior wood surfaces require no additional care beyond regular cleaning, according to Josko's product guide. The factory finish is designed to be low-maintenance.
If wood surfaces show signs of wear over time, contact your Josko Vertriebspartner (sales partner) for advice on specialist wood care products.
Aluminium Surface Care
Josko's exterior aluminium surfaces are either anodised (eloxiert) or powder-coated (pulverbeschichtet). Both are designed to be weather-resistant, but Josko makes clear that regular cleaning is essential to maintain the decorative appearance over decades, particularly in environments exposed to smoke, exhaust fumes, and aggressive airborne dust (Flugstaub).
Clean aluminium surfaces with a soft cloth and mild, pH-neutral cleaning solution. Rinse with clean water afterwards. Soap residue left on powder-coated aluminium attracts more dirt and creates a dull appearance over time.
For heavily soiled or chalked aluminium surfaces, Josko recommends the Innotec Service Set 4 for specialist cleaning and conservation. If the Innotec set does not achieve the desired result, contact your Josko partner for further advice.
Remember: this cleaning must happen at least twice per year, and you must keep written documentation and purchase receipts for the cleaning products, to maintain your aluminium warranty.
Hardware Maintenance
Josko recommends annual inspection and maintenance of all window hardware. Through daily use and natural building movement, hardware needs periodic adjustment.
Josko's concealed hardware (verdeckte Beschläge) requires specific attention. Before lubricating, use a dry cloth to remove old grease residue from all locking pins (Schließzapfen), corner bearings (Ecklager), corner hinges (Eckbänder), and scissor bearings (Scherenlager, also called Axerarm).
Josko recommends the following acid-free and resin-free lubricants:
- ROTO Beschläge-Fett: specifically for filling the patented grease depots on concealed hardware and moving parts.
- Haftöl in spray form (AX NR. 26-soma-0365).
- Haftschmierstoff "TecLine Beko" for tilt-turn hardware (DK-Beschläge), 500 ml spray.
After lubricating, open and close the window several times to distribute the grease evenly.
Josko warns that you should never use silicone spray, as it dries too quickly (evaporates) and does not provide lasting lubrication. This is a common mistake. Many people reach for silicone spray because it is readily available, but on Josko's concealed hardware it will not protect the moving parts adequately.
Check all screws for tightness. Tilt-turn mechanisms undergo daily stress, and screws loosen over time. If you notice that the window is dragging, not closing fully, or if the handle no longer reaches the vertical locked position, the hardware likely needs adjustment.
Hardware adjustments beyond basic lubrication and screw tightening should be done by a specialist. Contact Josko's customer service at kundenservice@josko.at or through the customer service form.
Seals and Gaskets
Inspect rubber seals (Dichtungen) during every cleaning. Look for cracking, hardening, or gaps. Functional seals are essential for thermal and acoustic performance.
Josko recommends a simple leaf test (Blatttest) to check seal integrity: close the window on a sheet of paper. If you can pull the paper out easily, the seal may need attention.
If seals appear damaged or the leaf test indicates reduced sealing, contact Josko's service team.
Drainage Channels
Check drainage openings (Entwässerungsöffnungen) at every glass cleaning. These channels allow water to exit the frame system. If blocked by dust, leaves, or debris, water can accumulate and affect both the window operation and the weather seal.
On Josko's ONE aluminium system, the drainage shaft is designed so that insect screens run within it, reducing tripping hazards and preventing dirt and leaves from getting caught. Clear these channels regardless.
Cleaning Frequency
Glass: minimum twice per year. Four times per year in urban environments, near busy roads, or in areas with high pollution or construction dust.
Aluminium exterior surfaces: at least twice per year (warranty requirement). More frequently in exposed locations or near sources of pollution.
Wood interior surfaces: twice per year with mild cleaning solution.
Hardware lubrication: at least once per year. Josko specifies the Ecklager and Axerarm (scissor bearing) as priority lubrication points.
Drainage channels: clear at every glass cleaning.
Seal inspection: at least once per year, or whenever you notice changes in window operation (drafts, noise increase, difficulty closing).
Joskomplett Premium: Extended Warranty and Professional Inspection
Josko offers Joskomplett Premium, a service package that extends the warranty on hardware and electronic components to 10 years (the industry standard is 2 to 3 years). The package includes a professional inspection by Josko technicians every two years, covering hardware, seals, glazing, construction joints, surfaces, and sun protection systems. It is a one-time payment with no subscription.
If you prefer to have Josko's own professionals handle the maintenance, Joskomplett Premium is worth considering. It does not replace regular glass cleaning, but it covers the technical maintenance that requires specialist knowledge.
What NOT to Do
Never use abrasive cleaners, steel wool, scouring pads, or razor blades on glass, wood, or aluminium. These can permanently damage surfaces.
Never use solvents, corrosive chemicals, or acidic products on any Josko surface. These can etch glass and damage coatings.
Never use high-pressure or steam-cleaning equipment on Josko windows. The Servicepass specifically warns against this.
Never use silicone spray on hardware. It evaporates too quickly and does not provide lasting lubrication. Use only the acid-free, resin-free lubricants that Josko recommends.
Never use microfiber cloths on wood surfaces. Use soft cotton cloths instead.
Never clean glass in direct sunlight. From my professional experience: soap water evaporates before you can squeegee it, leaving streaks. Clean in the morning, evening, or on overcast days.
Never let your aluminium cleaning records lapse. The warranty depends on documented proof of at least two cleanings per year with approved products.
Why Professional Technique Matters for Josko Owners
Josko windows are a significant investment. The combination of premium materials, award-winning design, and engineered hardware means that the windows will perform beautifully for decades, if they are maintained properly.
The glass-cleaning technique covered in this guide is the same method I use on every premium window I clean professionally. It works because it follows the physics of how soap, water, and rubber interact with glass. The Manifesto covers the foundation in five minutes. For the full professional method, including all three squeegee turns, extension pole technique, and advanced methods, the Beginner Program ($69, lifetime access) covers everything: the Mastery Course (90-minute video course), the AR Window Cleaning Training Tool for building muscle memory, and the Manifesto.
Combined with Josko's own Servicepass guidelines, you have professional training and manufacturer information at hand from both an external professional window-cleaning company and directly from the source.
Protecting Your Investment
Josko's vision is to create joy and value for your unique home. Regular, proper maintenance is how you protect that value. Clean the glass with professional technique. Follow the Servicepass for frame, hardware, and seal care. Document your aluminium cleaning. Keep your receipts.
The Window Cleaning Manifesto is free and takes five minutes. It is the foundation for every window you will ever clean, Josko or otherwise.
Your Josko Servicepass is available at josko.com/de/servicepass.
Justin Orloff is a professional window cleaner with 25+ years of experience, based in Vienna, Austria. He regularly cleans Josko wood/aluminium and aluminium windows across the Vienna region and created the world's first AR window-cleaning training platform. Based in Vienna, Austria.
