I thought this was an interesting read. In a hearing before the "Committee on Printing", which discussed the merits of hand presses and power presses, the famous engraver GFC Smillie discusses how he creates texture, contrast and color using lines and dots. http://goo.gl/oifQpV
A google search for George F.C. Smillie led me to this find. I was researching engravers for the educational series from a different thread.