Transparent and insulating materials having evacuated capsules

A method comprising:

• forming a composition consisting essentially of a plurality of hollow spherical silica shells within a solution;
• dispersing and suspending the hollow spherical silica shells within the solution such that a packing density of the hollow spherical silica shells within the solution is greater than 30%, and a visible light transmission of the solution is greater than 75%;
• processing the solution with a sol-gel method;
• and
• drying the processed solution to form a secondary shell of silica, wherein:
• the hollow spherical silica shells are integrated by the secondary shell to form a layer consisting essentially of the hollow spherical silica shells and the secondary shell,
• at least a portion of the hollow spherical silica shells have an internal volume at a pressure of less than 1 microtorr,
• each hollow spherical silica shell has a lateral dimension between 50 nm and 300 nm,
• the layer has a thickness between 3.175 mm and 6.35 mm,
• the layer has a thermal conductivity between 0.001 W/m-K and 0.02 W/m-K, and
• the layer has a visible light transmission of greater than 30% and less than 70%.