A Complete Guide to Different Types of Glass and Their Unique Properties

Most people have no idea what kind of glass is in their windows. They assume glass is glass. That assumption costs them money every single year, either in cleaning products that do not work, in damage they cannot explain, or in quotes from professionals who did not bother to check before they started.

I have been cleaning windows professionally since 1999, first in Melbourne, now in Vienna. Over 25 years across two continents, I have worked on everything from century-old heritage properties with hand-blown glass to floor-to-ceiling Sky-Frame installations with precision coatings worth thousands of euros per pane. The single biggest source of avoidable damage I have ever seen is not bad tools. It is ignorance about the glass itself.

This guide exists to close that gap. Whether you are a homeowner trying to understand your own property, or someone evaluating whether a window cleaner actually knows their craft, this is the Glasarten Eigenschaften Übersicht you need.

Why Does Glass Type Actually Matter?

Glass type matters because the same cleaning method that leaves one pane sparkling will permanently scratch or delaminate another. This is not a small risk. It is the difference between a clean window and a destroyed one.

The problem is invisible until it is too late. A scraper that slides effortlessly over standard float glass will tear straight through a soft Low-E coating in a single pass. The scratch appears immediately and is there forever. No polish, no professional restoration service, no amount of effort reverses it. The pane has to be replaced.

The same logic applies to cleaning chemistry. Alkaline solutions work well on heavily soiled standard glass. On acid-etched or sandblasted glass, the same chemistry can alter the surface texture, making it look patchy and dull in a way that was never there before. The cleaner did not fix the problem. They created a new one.

Understanding the Glasarten Eigenschaften Übersicht is not academic. It is the foundation of safe, effective cleaning.

Float Glass: The Baseline Everything Else Is Built From

Float glass is the reference point. Almost every other glass type starts here and is then modified through coating, tempering, laminating, or treatment.

It is produced by floating molten glass on a bed of molten tin. The result is a perfectly flat, optically clear sheet with consistent thickness across the entire pane. Standard float glass in residential use typically comes in 4mm, 6mm, or 8mm thicknesses. The thicker the pane, the better its acoustic and thermal performance, though neither is exceptional without additional treatment.

From a cleaning perspective, float glass is the most forgiving surface to work with. It tolerates a wide range of professional cleaning solutions, T-bar applicator technique, and squeegee work without risk of surface damage. A scraper can be used carefully to remove paint spots or mineral deposits, provided the glass is wet and the blade is new and held flat. A dry scraper or a blade at the wrong angle will leave a scratch even on standard float glass, but the margin for error is far wider than with specialty types.

Where people go wrong with float glass is assuming its tolerance extends to everything. It does not. Hard water deposits left to mineralize over months or years can etch the surface. At that point, the damage is chemical rather than mechanical, and removal requires specialist products. I cover this in detail in my guide on hard water stains on glass.

Tempered Glass: Stronger, But Less Forgiving on the Surface

Tempered glass is float glass that has been heated to approximately 620 degrees Celsius and then rapidly cooled. This process compresses the outer surfaces and puts the interior under tension. The result is glass that is four to five times stronger than standard float glass of the same thickness.

When tempered glass breaks, it shatters into small, blunt fragments rather than large, sharp shards. This safety property is why it is mandatory in building codes for shower enclosures, glass doors, side windows in vehicles, and floor-level glazing in residential properties. In Vienna's older residential stock, you see it most often in bathroom glazing, balcony doors, and ground-floor fenestration.

The cleaning consideration is this: tempered glass cannot be cut or drilled after the tempering process. It also cannot be scraped safely without risk. The reason is a phenomenon called nickel sulfide inclusions, tiny impurities that can cause spontaneous breakage years after installation. Aggressive mechanical action on the surface, particularly scraping, is a risk no professional should take without explicit knowledge of the pane's history and condition.

Tempered glass also frequently shows something called roller wave distortion, a subtle optical ripple visible in reflected light. This is a manufacturing artifact, not a cleaning problem. A first-time client who asks why their newly cleaned pane looks wavy in certain light deserves an honest explanation, not a puzzled shrug.

Laminated Glass: Safety Through Layering

Laminated glass is two or more sheets of glass bonded together with an interlayer, typically polyvinyl butyral or a resin. When laminated glass breaks, the interlayer holds the fragments in place. This is why car windscreens crack into a crazed web rather than falling apart, and why the glass in skylights and overhead glazing must be laminated by code.

In residential Vienna properties, laminated glass appears most often in skylights, overhead glazing, balustrades, and any glazed surface where a falling shard would be dangerous. Premium installations sometimes use it for acoustic dampening as well, since the interlayer absorbs sound transmission more effectively than a single pane of equivalent thickness.

Cleaning laminated glass requires attention to the edges. The interlayer is vulnerable to moisture ingress at the perimeter if edge sealing is compromised. Saturating the frame seal repeatedly with water-heavy cleaning methods can, over years, cause delamination visible as a cloudy or bubbly zone starting at the edge and moving inward. Professional technique uses controlled moisture application and keeps standing water away from edges and rebates.

The glass surfaces themselves clean like float glass of comparable thickness. The risk is at the perimeter, not the pane face.

Coated Glass: The Most Misunderstood Surface in Modern Buildings

Coated glass is where most cleaning damage happens, and where a Glasarten Eigenschaften Übersicht becomes genuinely critical knowledge rather than background reading.

The coating category covers several distinct products. Low-emissivity glass, universally called Low-E, has a microscopically thin metallic coating that reflects heat back into the room in winter and reflects solar heat away in summer. It is now standard in virtually every double and triple-glazed unit installed in Austria in the past fifteen years. The coating is invisible to the naked eye under normal conditions. Many homeowners do not know they have it.

Solar control glass carries a similar coating engineered to reduce solar gain, essential in south-facing floor-to-ceiling glazing where summer overheating would otherwise be unmanageable. Self-cleaning glass has a photocatalytic titanium dioxide coating on the outer surface that breaks down organic dirt in UV light and then allows water to sheet off cleanly rather than bead. Anti-reflective glass has a coating that reduces surface reflectance, used in museum display cases, high-end picture framing, and some premium residential installations.

Here is what matters practically. Some coatings are hard coatings, deposited during manufacturing through a pyrolytic process. These are embedded in the glass surface and are relatively durable. Others are soft coatings, applied after manufacture through a vacuum sputtering process. Soft coatings are on the inner surfaces of sealed double-glazed units and are never exposed to cleaning. But when a sealed unit fails and moisture enters, the soft coating can show degradation that looks like a cleaning failure. It is not.

The exposed outer coating on self-cleaning glass is delicate. Abrasive pads, scrapers, and strongly alkaline cleaners all damage it. Once damaged, the self-cleaning function is gone and the glass looks permanently patchy. I have seen this happen after a single aggressive clean by someone who did not know what they were looking at. The replacement cost for a large self-cleaning pane in a premium installation runs well into four figures.

Any window cleaner who cannot tell you whether your glass has a coating, and adjust their method accordingly, is working without the information they need. I wrote about this directly in why your window cleaner should understand glass coatings.

Patterned and Decorative Glass: Texture Changes Everything

Patterned glass is float glass that has been passed through textured rollers while still semi-molten. The resulting surface has a relief pattern on one side, providing privacy, diffusing light, or serving a decorative purpose. In Vienna's Altbau properties, you find it in bathroom windows, stairwell glazing, and entrance vestibules. The patterns range from the simple ribbed or hammered textures common in 1950s and 1960s construction to the elaborate pressed geometric designs found in Jugendstil and early 20th-century buildings.

The cleaning challenge is the texture itself. Dirt, pollution, and biological growth find their way into the surface relief and do not release easily under standard squeegee technique. The patterned face needs extended dwell time with the cleaning solution to loosen embedded soiling, and a soft brush agitation to work it out of the texture before the squeegee pass. A standard applicator-and-squeegee sequence without agitation leaves the recesses dirty even when the high points look clean.

On historic Jugendstil glass, the additional complication is fragility. Original hand-pressed glass from the early 1900s is often thinner and more uneven than modern equivalents. It cracks under pressure that modern patterned glass handles without complaint. Knowing which is which, and adjusting accordingly, is a judgment call that comes from experience with the buildings of that era.

Acid-Etched and Sandblasted Glass: Matte Surfaces With Special Needs

Acid-etched glass has its surface treated with hydrofluoric acid or an acid cream to create a smooth, uniform matte finish. Sandblasted glass achieves a similar visual result through mechanical abrasion with fine silica or aluminum oxide particles. Both are used where diffused privacy is needed without the patterned look, and both are common in Vienna's premium residential market in bathroom enclosures, internal glass partitions, and entrance screens.

The matte surface is porous relative to clear glass. Fingerprints absorb into it rather than sitting on the surface. Mineral deposits from water contact bond into the micro-texture. Standard glass cleaner smeared across a sandblasted surface with a squeegee often leaves the appearance of clean while pushing contamination deeper into the surface profile.

Correct cleaning uses a pH-neutral solution, a soft microfibre application with gentle circular agitation, and a clean damp wipe rather than a squeegee. The technique is slower and more deliberate than standard window cleaning. Anyone who rushes an acid-etched panel with the same system they use on clear glass will leave it looking worse than before, streaked with dried solution in a pattern that takes significant effort to correct.

Insulated Glazing Units: The Sealed System Question

A double or triple-glazed sealed unit is not a glass type in itself. It is a system, typically two or three panes of glass separated by a spacer bar and sealed at the perimeter to create an insulating air gap or gas-filled cavity. The glass within those units can be any combination of the types above: clear float, tempered, laminated, coated, or combinations thereof.

The cleaning consideration for sealed units is seal integrity. The perimeter seal keeps moisture out of the cavity. When it fails, condensation appears between the panes, visible as a hazy or streaky film that cannot be reached from either surface. This is a unit failure, not a cleaning problem, and cleaning cannot fix it. The unit needs replacement.

A common scenario I encounter: a client has had the same persistent haze for two years despite multiple cleaning attempts. When I examine the pane closely, the haze is internal, between the panes, not on the surface. The cleaning was never going to work. What they needed was a glazier, not a window cleaner. Part of honest professional service is telling someone that truth rather than taking their money for a job that cannot be done.

What This Means for Anyone Who Owns Glass in Vienna

Vienna's residential stock spans roughly 150 years of glazing technology in active use simultaneously. A property in the 19th district might have original single-pane float glass in restored timber sashes sitting two meters from a modern floor-to-ceiling triple-glazed unit with Low-E coating. The same cleaning approach applied to both is a mistake.

Older properties in Hietzing, Döbling, and Währing frequently combine heritage glazing with modern thermal upgrades, sometimes within the same window reveal. Recognising the difference on sight, understanding what each surface needs, and having the right chemistry and tools for each, is what separates a specialist from a general cleaner who does windows on the side.

I referenced the Altbau context in more detail in what 25 years of cleaning windows taught me about buildings, if you want to read further on how Vienna's architecture creates specific cleaning demands that do not exist in newer construction.

The 95% repeat-client rate I see year after year is not an accident. It comes from doing the assessment correctly before touching a single pane, identifying the glass, checking the coatings, understanding the frame material and seal condition, and then applying the right method. That first assessment takes minutes. Getting it wrong costs far more.

How to Talk to a Window Cleaner About Your Glass

You do not need to be an expert. But knowing a few questions to ask separates the professionals from the generalists immediately.

Ask whether they check for coatings before they start. The answer should be yes, always, as part of the assessment. Ask what they use on matte or etched surfaces. If they describe the same method they use everywhere, that is your answer. Ask whether they carry a pH meter or test their solutions. A professional who works across multiple glass types should understand the chemistry they are using.

Ask what they do if they are unsure about a surface. The right answer involves caution, testing in an inconspicuous area, and transparency with you about the risk. The wrong answer is confidence without information.

You are not testing them to be difficult. You are protecting glass that represents a significant part of your property's value and thermal performance. The questions are reasonable. A professional will welcome them.

Ready for a Window Cleaner Who Actually Knows the Difference?

If your property has coated, tempered, laminated, patterned, or heritage glass, and most Vienna homes have at least two of those, you need someone who identifies before they clean, not someone who applies the same method to every surface and hopes for the best.

I personally assess every property before I quote. No assumptions. No one-size-fits-all chemistry. Every job is quoted individually after I understand exactly what I am working with.

If that sounds like the standard your windows deserve, write to me here and I will come back to you within one working day.

Frequently Asked Questions

What is the most common glass type in Vienna residential properties?

Standard float glass remains the most common single pane type, particularly in pre-1990 construction. However, modern renovations and new builds almost universally use insulated glazing units with Low-E coatings. A Glasarten Eigenschaften Übersicht for any Vienna property built or renovated in the last 15 years will typically include at least one coated glass type.

Can I use a glass scraper on my windows at home?

Only on standard float glass, and only with a new blade held flat against a wet surface. Never use a scraper on tempered glass, coated glass, or any pane you cannot positively identify as uncoated float. The risk of permanent scratching is real, and the damage cannot be reversed.

How do I know if my windows have a Low-E coating?

Hold a lit candle or lighter near the glass and look at the reflections. Standard glass reflects two images of the flame. A coated pane reflects a slightly different color in one of the reflections, often greenish or bluish, because the coating changes how light reflects. A professional can identify it on sight in most cases without this test.

What is the difference between acid-etched and sandblasted glass in terms of cleaning?

Both have matte, porous surfaces that require pH-neutral chemistry and gentle agitation rather than standard squeegee technique. Acid-etched tends to have a finer, smoother texture; sandblasted is slightly coarser. Both are damaged by abrasive products or alkaline cleaners. In the Glasarten Eigenschaften Übersicht, they sit in the same care category: handle gently, clean slowly, never rush.

Why does my double-glazed window have haze between the panes that cleaning never removes?

That haze is internal condensation from a failed perimeter seal on the insulated glazing unit. No cleaning from either outer surface will reach it. The unit needs to be assessed by a glazier for replacement. A window cleaner who tells you otherwise is either mistaken or not being honest with you.

Does self-cleaning glass actually work, and does it still need professional cleaning?

Self-cleaning glass uses a photocatalytic coating that breaks down organic dirt in UV light and allows water to sheet off rather than bead. It reduces maintenance frequency but does not eliminate the need for cleaning. Mineral deposits, non-organic soiling, and areas shaded from direct UV still accumulate normally. Professional cleaning with the correct pH-neutral chemistry preserves the coating; the wrong products degrade it permanently.