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