Coated glass is coated on the glass surface with one or more layers of metal, alloy or metal compound film to change the optical properties of the glass to meet a specific need. Coated glass can be divided into heat reflective glass, low-emissivity glass, conductive film glass, self-cleaning glass, and so on. According to the different process, it can be divided into on-line coating and off-line coating. On-line coating means that the coating process is performed on the float line, and off-line coating is performed after the flat glass is shipped from the factory. Off-line coating has very strict requirements on the freshness, surface quality and cleanliness of the original glass sheet. Generally, the coating process must be completed within a short time after the original sheet is produced, otherwise the coating quality will be greatly reduced. The surface defects of the coated glass are generally visible to the naked eye, such as bubbles, streaks, spots, spots, scratches, and corrosion marks on the surface of the film. Before purchasing the original film, it is necessary to thoroughly understand the quality control level of the manufacturer; when entering the warehouse, the production date, certificate of conformity and technical documents must be verified. The orientation of the film surface of the coated glass during deep processing will directly affect the quality of the product, which involves a film surface discrimination problem. Membrane surface discrimination methods are as follows: First, the instrument detection method. 1. A professional membrane surface detector can be used, which is convenient, fast, and accurate. The plastic surface is in contact with the glass without scratching the glass. Its greatest advantage is the sealing of the coated glass membrane surface (such as hollow and sandwich layers). Which film can be measured? 2. Measured by a self-made membraner, the small multimeter can be converted into a membraner. Because the coating layer is a metal material, the surface of the film can be identified by a resistance measuring method, which is convenient to use and difficult to scratch the glass. Second, the induction test method. With the induction pen provided by Glavey, one hand touches the membrane surface, the other uses a sensor pen (the finger touches the sensor pen electrode), and touches the measured surface with the pen tip. If you see the light or hear the chirping, you can judge For the film surface, the pen is designed based on the principle of film conductivity; Third, empirical observation method. 1. Experienced employees touch the surface of the glass with their hands. The smooth surface is a glass surface and the non-smooth surface is a film surface. However, it is difficult to judge the accuracy of high-quality coated glass, film surface and glass surface. This method is simple and easy, but it will inadvertently damage the membrane surface; 2. Using light or lighter light, looking into the glass, if there are two lights, shadows, red and light sides are the film surface, and the light and shadow have no change. 3. Using a pencil to see the shadow judgment, a pencil with a good head will be penetrating, and the tip of the pen will touch the surface to be measured (45°-60° is appropriate). If we can see from this face that the two shadow faces are non-membrane, the other side is Glass surface (this method is especially suitable for heat-reflective coated glass). 4. As the coated glass is cut by the manufacturer, the film is strictly required to face upwards. This can be judged according to the sign of the edge of the glass after cutting. The rough edge is the film surface, and the flat edge is the glass surface. Fourth, with the method of discriminating glass surface. With the self-made ultraviolet tin surface meter, the film surface can also be measured, that is, the non-tin surface is a film surface. In addition, it should be noted that the heat reflecting glass film layer is not conductive, and methods 1 and 2 are not applicable.