Since liquid crystals transmit {HEAD ~ only about 15%} of {TAIL ~ any incident light}, the black light absorbing material facilitates observation and measurement of color changes in the liquid crystal material against a dark background 
Since liquid crystals transmit { HEAD ~ only about 15 % } of { TAIL ~ any incident light } , the black light absorbing material facilitates observation and measurement of color changes in the liquid crystal material against a dark background
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH