A dye or other colorimetric substance may be added to {HEAD ~ the catalyst solution} to allow for {TAIL ~ visualization} of the amount and location of catalyst solution on the substrate 
A dye or other colorimetric substance may be added to { HEAD ~ the catalyst solution } to allow for { TAIL ~ visualization } of the amount and location of catalyst solution on the substrate
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH