Why Do Some Glass Units Look Blue?

If you have ever looked at a modern window or glazed door and noticed that the glass appears to have a subtle blue tint, you might have wondered why. Is the glass actually blue and what does this tell you about the glass unit?

Why Does Glass Look Blue?

Glass is generally thought of as completely clear, but in reality, it can have a very slight natural colour. Standard glass contains small amounts of iron, which can give it a subtle green hue, particularly when you look through thicker pieces of glass.

However, when a glass unit appears blue from certain angles, the colour is often linked to a coating. This coating is applied to the glass during manufacturing. Modern double and triple glazing can include specialist coatings to improve thermal, solar or optical performance. These coatings can alter how light reflects and passes through the glass. As a result, they can sometimes create a noticeable blue or green appearance.

Low-E Glass Can Have a Blue Appearance

One of the most common reasons modern insulated glass units can appear slightly blue is the use of Low-E glass.

Low-E stands for “low emissivity”. These coatings are designed to improve the thermal performance of glazing by reducing the amount of heat that is lost through the glass.

A Low-E coating works by reflecting a significant amount of long-wave infrared radiation back towards the interior of a building. This helps keep more heat inside rather than allowing it to escape through the window.

Depending on the particular Low-E coating used, the glass may have a subtle colour or reflective appearance when viewed from outside. This is one of the reasons you may see blue or blue-grey tones on newer, high-performance windows.

What About Solar Control Glass?

Solar control glass is another type of specialist glazing that can sometimes have a distinctive appearance, including blue or blue-grey tones.

As the name suggests, solar control glass is designed to help manage the amount of solar energy entering a building.

Large areas of glazing can allow significant amounts of sunlight and solar heat into a property. While natural light is desirable, excessive solar gain can cause rooms to become uncomfortably warm, particularly during the summer months.

Solar control glass can help reduce the amount of solar energy passing through the glazing while still allowing natural daylight into the space. Different solar control coatings are available, and they can produce different levels of reflectivity and colour. Some may appear relatively neutral, while others can have more noticeable blue, silver, grey or green tones.

Why Does the Colour Look Different From Different Angles?

You may have noticed that a window can look blue from one position and almost completely clear from another. Again, this is largely down to reflection.

The amount of light reflected from a glass surface changes depending on the angle at which you are viewing it. The surrounding environment also plays a major role.

A window looking towards a bright sky may reflect a lot of blue, whereas a window facing a darker building or shaded area may appear much more neutral.

The size of the glass, the surrounding frame, the direction the window faces and the amount of natural light can all influence its appearance.

Why Is Glass Sometimes Green Instead of Blue?

Blue is not the only colour you may notice in modern glazing.

As mentioned earlier, ordinary glass can have a subtle green tint because of the iron content naturally present within the material. This can become more noticeable when looking through thicker glass or viewing the edge of a pane.

Glass Options

At UKO Glass, we offer a wide range of glass options to suit different requirements, including Low-E, Ultra-Low E and Solar Control glass.

We also offer self-cleaning glass options, including ClearGlaze and BlueGlaze, as well as laminated glass options suitable for applications where additional safety and security performance is required. If you’re looking for the right glass specification for your next project, drop us an email on theteam@ukoglass.co.uk.