The strength of {HEAD ~ the bond} can be varied by varying {TAIL ~ the amount} of the impregnant 
The strength of { HEAD ~ the bond } can be varied by varying { TAIL ~ the amount } of the impregnant
OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH