When you take a close look at the vacuum insulated glass for the first time, you might wonder why the glass has some evenly distributed tiny black spots, what these black spots do, and if they will affect the clarity of the glass. As a matter of fact, they are called spacers and are an essential part of vacuum insulated glass.
Vacuum insulated glass is made of two parallel panes of glass separated by an evacuated gap. The glass panes will be pressed together under atmospheric pressure and affect the vacuum space. To ensure the vacuum space can withstand the atmospheric pressure, spacers are placed between the two glass panes to maintain the separation. Spacer design is a key factor in the manufacture of vacuum insulated glass:
1. To prevent the increase of thermal conductivity and reduction of glass clarity, the size and overall quantity of the spacer should be minimized;
2. However, if the size of the spacer is too small, under the atmospheric pressure, the load will be concentrated in the spots where glass panes and spacers contact, causing excessive surface stress in the glass panes and easy breakage;
3. Spacers take many different shapes. The cylinder is the shape used most often. Other shapes include square, oval, linear, and grid;
4. They can be made of stainless steel, carbonized tungsten steel, chromium steel, aluminum alloy, nickel, molybdenum, tantalum, and ceramics;
Because of the uneven thickness and waviness in the glass, a glass pane may not be totally flat. While all spacers have the same specifications, there might be areas where the gap between the parallel panes is larger than the height of the spacers, causing spacers to gradually move away from their original positions. The uneven load on spacers will reduce the life of the vacuum insulated glass. To mitigate the likelihood of breakage, flexible spacers in linear or grid shapes are often employed, with at least one end coated with low-melting metal or solder glass or fine wires to get spacers interconnected.