If somebody tries to sell you cheap reflective glass saying it is “Hard Coated”, the first thing you should ask is “Is it spray hard coat or CVD hard coat?”. Spray hard coat could be termed as a primitive and is relatively cheaper, in this one the chemical composition is sprayed over glass which would be in a semi solid stage (online process). Most cases, the coating tends to be uneven and deposition rate would be poor. In most cases the coated side appears yellowish.
CVD (Chemical vapor deposition in atmospheric pressure) on the other hand is far superior and the latest. Here, the chemical composition is vaporised and then allowed to deposit on semi-solid glass (online coating) in a controlled manner, achieving high deposition rate and the coating would be even. In most cases, the coated side would have a silver appearance.
It would be a disaster if spray coated glasses which come at cheap rates are used (especially when it is mis-sold with the name “Hard coated reflective glass”) in buildings. Below are some pictures for reference.
CVD Hard Coated Glass also offer better aesthetics- both internal and external
Click Here to read more on Hard Coated / Pyrolytic Coated Glasses.