The resulting mixture is then stirred and optionally heated over a sufficient period of {HEAD ~ time} to bring about {TAIL ~ formation} of the dye product 
The resulting mixture is then stirred and optionally heated over a sufficient period of { HEAD ~ time } to bring about { TAIL ~ formation } of the dye product
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD OTH OTH OTH TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH