As environmental protection requirements become more stringent, printing inks are almost always required to use water-based inks, and various coatings, varnishes, etc. are also required to use water-soluble materials. Because of the specific heat capacity of water and the heat of vaporisation are very high, the evaporation of water solvents is much more difficult than traditional inks. The chemical composition of the ink and coating itself is mostly organic polymers, and they need to be heated up quickly to promote polymerisation. Infrared heating method than the traditional hot air heating naturally has a lot of advantages, such as very high energy density, good penetration, coating inside and outside the almost simultaneous drying, speed and so on. But which of the various infrared light sources is best?

Infrared emitters can be roughly divided into shortwave (0.8-1.4um), mediumwave (1.5-3.0um) and longwave (3.0-10um) according to wavelength. Since the infrared absorption of water is mainly at 3.0um and 4.5um with two very strong peaks, the That's why it's better to use medium and long waves.But because of the long-wave infrared (ordinary ceramic or stainless steel heating tubes) compared to medium-wave infrared (resistance wire transparent quartz tubes) has several major disadvantages: slow reaction speed, poor penetration, power density is smaller.That's why medium wave emitters are the best choice。In addition, medium wave tubes can have a gold plated reflective layer, which is more efficient than the usual aluminium metal reflector plate, and is not oxidised in high temperature environments, and there is no worry about reduced reflectivity due to dust. Of course the thermal efficiency of the medium wave tube is screwed up much more. At the same time, due to the fast reaction speed, the temperature control is much better.

However, short-wave infrared still has some applications in certain fast drying departments where very high energy density is required. Because its power density can be very large, and the reaction speed is very fast. These are medium wave lamps can not do. Although it is said that the wavelength of the short-wave lamp and the absorption of water and polymer materials do not match, short-wave lamp near the air temperature is very high, if the heated material, such as paper and the lamp is very close to the distance, the hot air can also play an effective supplementary heating effect. The result is also still good. However, for ink and paper that are sensitive to high temperatures, short-wave lamps are not suitable.

In summary，For drying applications of water-based inks and coatings, both medium-wave and short-wave infrared drying are available options. And medium wave infrared is the best choice in most cases.