The Solar Panels Plus factory receives the clear glass tubes from the glass factory. When the tubes are delivered they are single wall glass pipes that are open on both ends.

Two sizes (47mm and 58mm) of borosilicate glass tubes are used, shown here they are still in the shrink wrapped bundles used to prevent breakage in transit from the glass company.

The first step in the process is preparing one end of the 47mm tube (this will become the inner layer of the double wall tube).

The tubes are now ready to have the selective absorber optical coatings applied.

A special deposition process applies the optical coatings to the smaller 47mm tube. This tube will become the inside wall of the double wall tube.

This open-source coating technology was initially developed under sponsorship of the Chinese government, and has subsequently been modified through further development for improved performance.

The coatings used by the SPP factory consists of a high performance proprietary blend of aluminum, copper, and steel and other materials.

After the 47mm tube has been given it's selective optical coating it is ready to be placed inside the 58mm tube.

At one end of the now-double walled tube, the inner and outer wall are sealed together to form an inner wall, and outer wall, and an empty area in between that will become the vacuum area. The other end of the outside tube still has a small opening to apply the getter and create the vacuum.

The tubes are then inserted into a special machine that will add the getter, pump the evacuated space down to vacuum, and seal the end.

At this point the tubes are ready for final trimming, cleaning and testing.