There are a number of different types of original prints to be aware of. Intaglio prints: for example a dollar bill-the bills we handle and most stamps we use are engraved in metal plates and are printed after a viscous ink (about the consistency of oil paint) is forced into grooves, scratches, etched lines or indentations. The polished surface is then wiped clean using newsprint and tarlatan, leaving ink only below the plate level. The plate is then covered with a dampened paper and felt blankets. It is run through the press where great pressure ( like 8 tons to the square inch) pushes the paper down into the engraved or etched grooves to pick up ink. In other words, in intaglio we see printed what is below the surface of the plate and the ink is now embossed on the paper. Among the greatest masters of engraving and etching are Durer, Holbien, Rembrandt, Goya, and Picasso. Color viscosity printing is among the latest developments in intaglio printmaking. Stanley William Hayter in Paris developed it during the late 1960s. I will discuss this later.
Etching: The artist creating etchings does so on metal plates. These can be copper, zinc, or rarely steel. Ordinarily a polished metal such as 16, 18 or 20 gauge is ideal. I prefer working with copper because it can be more easily engraved than zinc. One needs to have access to an etching press on which to edition and proof the plate during its development. Other material requirements include an acid bath in which to etch the plate; good quality paper; tools,such as scrapers, burins, a burnisher, brushes, pencils, etc. materials such as tarlatan, felt blankets, inks, various grounds, rosin, asphaltum, wax ball grounds, brayers, putty knives, and razor blades.
There are many approaches to creating an etching. Rembrandt van Rijn, 17th Century painter and printmaker, produced prints that were printed in either brown or black. He created more than 300 plates in a wide range of subject matter-portraits, landscapes, religious works, and studies of everyday life. They usually were a combination of dry point and etched line combined with scraping and burnishing.
The colors usually are applied to the plate in the following manner. First, the intaglio color is applied to the entire plate and it is wiped. (The plate could be inked a la poupee with several colors using small wads of tarlatan for each color.) In this first application the ink is of a consistency- that is-- it has sufficient oil added to it that approximately a teaspoon of it on the blade of a putty knife will "run" and "break"- "run" and "break" above the glass slab, and the plate is wiped!
Second, The hard roller is charged with the runniest ink. The hardness of the rubber roller is its "durometer." Ideally, a hard roller should be 35 durometer. The soft roller should be 15 durometer. By a runny ink I'm saying thinner than cream. In fact, Hayter used to say, "Think milk and honey" when you want to remember the order of ink application. Milk on the top level and honey in the lower level. The hard roller passes over the plate with little or no downward pressure. You don't want that color to go into the lower levels.
Thirdly, the soft roller is now charged with the third color. This color is thinned with the same oil but is not as runny as the previous color. It is applied with some downward pressure so that it inks the lower level. Voila! This color does not mix with that applied previously with the hard roller. Finally, a fourth color can be applied. This color should be mixed with plate oil where the others are mixed with either thin litho oil or boiled linseed oil. It is rolled out on the glass slab as a rather thin film. The plate with its three colors on it is placed face down on the ink film and the back of the plate is struck with your hand or a soft rubber hammer. This is called "contact printing" and in this instance only the highest parts of the surface will accept the "contact" color. Now, it is ready to be placed on the press bed, the dampened paper has been brushed and waved in the air to assure only dampness- no wetness-- is carefully lowered onto the plate, the felt blankets are placed over both the plate and paper-and the press bed is cranked thru and back out. The moment of truth has arrived. The proof is in the printing.
Then there are other effects possible with selective wiping using small bits of phonebook paper or even Q-tips. Editioning with a little practice can produce very consistent results. So far I haven't seen a really good written explanation of the above approach. I suggest you look at the prints of Krishna Reddy who was Hayter's Assistant when I was in Paris in 1969.
Printmaking: History and Process
Donald Saff and Deli Sacilotto
1978 Holt, Rinehart and Winston
The Complete Printmaker
1972 Holt, Rinehart and Winston
The Art of the Print