Offline coatings are added after the basic float (or annealed) glass has been manufactured and cut.
Offline coatings were previously considered less resistant but latest techniques now use a magnetron coater which results in an exceptionally durable coating, which can even be heat treated for toughening.
The magnetron coater uses a technique known as sputtering to apply layers of metal oxide to the glass under vacuum conditions. This offline process allows a much wider range of formulas to be used, including those with reflective properties needed for solar protection and the most energy effective forms of Low E glass. The result is a microscopically thin layer of coating which gives the glass superior clarity and transparency.
Below is a comparison of two Low E glasses – one which has been manufactured online and one using the offline magnetron coater process. You will see that the offline coated glass has a much more neutral, transparent appearance.
All offline coatings are produced on a magnetron coater. It is the developments in the coatings which makes them more durable.