the polycondensation of resorcinol with formaldehyde under alkaline conditions results in the formation of surface functionalized polymer &# 34 ; clusters &# 34 ;. the covalent crosslinking of these &# 34 ; clusters &# 34 ; produces gels which when processed under supercritical conditions , produce low density , organic aerogels . the aerogels are transparent , dark red in color and consist of interconnected colloidal - like particles with diameters of about 100 å . these aerogels may be further carbonized to form low density carbon foams with cell size of about 0 . 1 micron .