To identify old window glass, look for visual distortions. Authentic antique glass (pre-1900s) was hand-blown or cylinder-rolled, resulting in a characteristic "wavy" texture and tiny trapped air bubbles. Modern glass, by contrast, is perfectly flat and smooth.
Identifying the type of glass in your windows is essential for understanding its performance in terms of safety, energy efficiency, and durability. One of the easiest ways is to look for a manufacturer's label or etching in the corner of the pane, which often indicates if the glass is tempered, laminated, or Low-E.
Here's a simple way to tell: ✅ Check the Etching: Look at the corner of the glass — most windows have a small etched code or logo (like “LoE 2005” or a manufacturer's name and date). That number often tells you the year the glass was made, which is usually the same year the window was installed.
There are seven different things you can do to find your window manufacturer, all of which should only take a few minutes of your time.
Cylinder glass is one type of antique, mouth-blown window glass found in historical buildings dating back to the 1600s. It's also known as wavy glass for the bubbling, undulating imperfections found in the surface of the glass that distort images when you look through it.
If there is no mark on the glass, there may be other signs that can help you work out how old it is. It may have mould marks, show the pontil mark of blown glass or have identifying characters within the glass, such as bubbles. All of these can help you find out more about your glassware with a bit of research.
Manufacturer print – Check the corner of your double-glazed windows to see if there's a date for when it was manufactured, or a serial code. If the double-glazing is safety, toughened or laminated glass panes, the manufacturer date will always be present – but these are the only instances where that is mandated.
The four main types of windows are Double-Hung, Casement, Picture, and Awning. These categories are primarily defined by how the window operates, its ventilation method, and its overall function in the home.
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To determine if your vintage glassware is valuable, look for signature brand markings, unique colors (like uranium green or cranberry pink), and intricate textures or etchings. Many everyday pieces from the 1920s–1960s are worth money if they are from highly collected makers.
To date glass, examine its manufacturing method, mold seams, and maker's marks. Look for rough pontil scars on the bottom, which indicate pre-1860 hand-blown glass. Modern mass-produced glass made after 1910 will feature smooth finishes and mold seams that run all the way over the lip.
Not all Fenton glass has a maker's mark. Pieces manufactured before 1970 usually only had paper labels, which were easily lost. Fenton started permanently stamping their oval logo into the glass in 1970, though some 1990s and later pieces may still lack marks because the mold stamp didn't press deeply enough.
There are four main types or strengths of glass:
While ancient China, Korea and Japan widely used paper windows, the Romans were the first known to use glass for windows around 100 AD. In England animal horn was used before glass took over in the early 17th century. Frames were made in timber and windows were small to suit the glass.
No, not all tempered glass has a stamp. While most commercially manufactured tempered glass (like windows, shower doors, and automotive glass) is permanently etched or stamped by the factory, you may not find a stamp on custom-cut pieces, older glass, or aftermarket screens.
Look for labels or any stickers, which can be at the bottom of the frame, on the sides, or on the sash. They can also be on the windowsill, the casing, and the jambs. Check for markings on the window frame or the hardware.
The oldest version of Windows is Windows 1.0, released on November 20, 1985.
Click the Start or Windows button (usually in the lower-left corner of your computer screen). Click Settings. Click About (usually in the lower left of the screen). The resulting screen shows the edition of Windows.
The following will explain the most common types and their uses.
Microsoft Windows has evolved significantly since its inception in 1985, growing from a simple MS-DOS graphical layer into a foundational global operating system. The platform's history includes 15 major iterations, spanning the original graphical shells, the unified 32-bit NT era, and modern annual feature updates.
To check the age of your house windows, inspect the glass corners for etched manufacturer codes, or look at the metal spacer bar between the panes for a stamped date. You can also check for warranty paperwork or builder stickers usually placed on the inside of the frame.
To date glass, examine its manufacturing method, mold seams, and maker's marks. Look for rough pontil scars on the bottom, which indicate pre-1860 hand-blown glass. Modern mass-produced glass made after 1910 will feature smooth finishes and mold seams that run all the way over the lip.
In the 1700s, window glass was made by hand using either the crown glass or cylinder glass methods. Because creating large, flat sheets was technologically impossible at the time, molten glass was blown into shapes, flattened, and cut into small rectangular or diamond-shaped panes.