With the development of Low-E glass, Low-E glass is more and more popular in the construction market for its superior energy saving performance. The production of Low-E glass in China has been increasing at a high speed. Due to the increase of sales volume and the maturity of manufacturing level, the price of Low-E glass has also decreased. The application range has been rapidly expanded from the first high-grade public buildings to ordinary civil buildings. So how to distinguish common glass from Low-E glass? In practical application, if it is known that it is Low-E glass, it is relatively simple to distinguish the position of Low-E film surface. However, due to the particularity of Low-E glass, it is difficult for ordinary personnel to distinguish the difference from ordinary coated glass or even non coated glass only in appearance.

1. The most accurate method to identify Low-E glass by photometer is to measure the surface emissivity of glass by far infrared spectrophotometer. According to gb/t18915.2-2002 standard for low radiation coated glass, the off-line Low-E glass radiation rate is ≤ 0.15, and the online Low-E glass radiation rate is less than 0.25. this is also the method used by the authoritative glass detection organization.

But because only small pieces of single glass can be detected, hollow glass must be disassembled into single glass before it can be carried out. At the same time, because the far infrared spectrophotometer is expensive, this method is not suitable for the rapid determination of processing and using on-site.

2. In the method of field determination, the single Low-E glass is discriminated. At present, the application of single chip Low-E in domestic market is Yaohua online Low-E glass, which can be tempered, hot bent, laminated and other deep processing like ordinary glass. This kind of glass can be measured and judged by portable surface radiation rate measuring instrument, but the more simple and practical method is surface resistance measurement.

3. The thermal reflection of Low-E glass is actually the result of the free electrons and electromagnetic wave of the film, so the surface of Low-E glass is conductive.

The surface resistance of ordinary non coated glass is infinite. The surface resistance of sunlight controlled coating glass will decrease, but it is still very high. The block resistance on the Low-E glass surface is generally below 20 ohms.

We can identify quickly by using this feature. The square resistance value of glass surface shall be measured by four probe tester. The square resistance can be measured by placing the measuring head on the dry and clean glass surface. The square resistance can be converted into radiation rate through relevant formula, so as to determine whether it is Low-E glass.

It can also be simply judged by using a common multimeter. Place the tip of the multimeter on the glass surface, with the distance between the positive and negative tip about 1cm. At this time, if the displayed resistance value is tens of ohm, it can be judged as Low-E glass film surface. If it is more than 100 ohm, it is not a low-E glass film surface. However, this method is easy to be affected by the distance between the tip and the contact pressure and contact area, so it should be measured several points to determine comprehensively.

4. When synthesizing hollow glass, the Low-E film surface is placed in the hollow glass, so it is difficult to determine whether the Low-E is used.

Although the Low-E hollow glass has a much lower heat transfer coefficient than ordinary hollow glass, it is not easy to quickly measure the heat transfer coefficient of glass in the field. At present, the Low-E glass is still used as the relatively simple method without destroying the hollow glass.

A weak magnetic field is produced by using electromagnetic coil or capacitance. When the Low-E glass coated with conductive film is close to the electromagnetic field, the electromagnetic field state will be changed, which will affect the output current or output voltage.

According to this principle, we can detect whether there is Low-E film in the hollow glass, and we can know whether the distance of Low-E film is far or near according to the change size. At present, the Low-E film surface tester with mature technology in the market is based on this principle. The hand-held Low-E tester is placed close to the surface of the hollow glass, and press the test button to determine whether there is Low-E film surface according to the flashing state of the indicator light.

This method is quick and simple, and it does not need to disassemble the hollow glass, so it has good popularization value. However, if the hollow glass area is too small, the detection results are easily affected by the aluminum strip or window frame at the side, and the test results are not authoritative. That is, when the instrument determines that there is a low-E film, it cannot be guaranteed that it must be a low-E product that meets the standard.

5. Image measurement method is now spread to identify the match or bright object in front of the window glass, observe four images (in other words, there are 4 flames or 4 objects) in the glass. If the Low-E glass has one image color different from the other 3 images, if the color of the four images is the same, it can be determined that the Low-E glass is not installed.

This method is based on the principle that even colorless high permeable Low-E glass will have a little light reflection color, which is only suitable for simple discrimination between white glass and colorless Low-E hollow glass.

6. There are other simple identification methods for hollow Low-E glass, although each has its own limitations, it is helpful for comprehensive use. When offline Low-E synthetic hollow, the edge film layer should be removed, so it can be judged by checking whether there is a boundary between glass and film at the position near the spacer bar.

When Low-E hollow is online, the edge film is not removed, so it can also be determined by resistance method where the edge sealant is not covered on the inner surface of the glass.

In conclusion, the identification method of single Low-E glass is simple, and it is difficult to determine the hollow Low-E accurately without dismantling. At present, many researchers are studying more practical detection instruments.