Mostly manufacturing, I believe. If memory serves me, the process involves supercritical drying--you put a liquid-based gel into a vessel under very high temper

Mostly manufacturing, I believe. If memory serves me, the process involves supercritical drying--you put a liquid-based gel into a vessel under very high temperature and pressure until the gas/liquid states become interchangeable, then gradually remove the supercritical fluid, tweaking the temperature as needed, until enough fluid is removed. Once brought back to STP, the gel structure is left behind in the same form it had with the liquid medium, but with all the liquid removed. Mistakes at almost any step in the process will permanently ruin the batch of gel, of course.