Prior to the invention of woodblock printing, seals and stamps were used for making impressions. The oldest of these seals came from Mesopotamia and Egypt. The use of round "cylinder seals" for rolling an impress onto clay tablets goes back to early Mesopotamian civilization before 3000 BC, where they are the most common works of art to survive, and feature complex and beautiful images. A few much larger brick (e.g. 13×13 cm) stamps for marking clay bricks survive from Akkad from around 2270 BC. There are also Roman lead pipe inscriptions of some length that were stamped, and amulet MS 5236 may be a unique surviving gold foil sheet stamped with an amulet text in the 6th century BC. However none of these used ink, which is necessary for printing (on a proper definition), but stamped marks into relatively soft materials. In both China and Egypt, the use of small stamps for seals preceded the use of larger blocks. In Europe and India, the printing of cloth certainly preceded the printing of paper or papyrus; this was probably also the case in China. The process is essentially the same—in Europe special presentation impressions of prints were often printed on silk until at least the 17th century.
The wood block is carefully prepared as a relief pattern, which means the areas to show 'white' are cut away with a knife, chisel, or sandpaper leaving the characters or image to show in 'black' at the original surface level. The block was cut along the grain of the wood. It is necessary only to ink the block and bring it into firm and even contact with the paper or cloth to achieve an acceptable print. The content would of course print "in reverse" or mirror-image, a further complication when text was involved. The art of carving the woodcut is technically known as xylography, though the term is rarely used in English.
For colour printing, multiple blocks are used, each for one colour, although overprinting two colours may produce further colours on the print. Multiple colours can be printed by keying the paper to a frame around the woodblocks.
There are three methods of printing to consider:
In addition, jia xie is a method for dyeing textiles (usually silk) using wood blocks invented in the 5th-6th centuries in China. An upper and a lower block is made, with carved out compartments opening to the back, fitted with plugs. The cloth, usually folded a number of times, is inserted and clamped between the two blocks. By unplugging the different compartments and filling them with dyes of different colours, a multi-coloured pattern can be printed over quite a large area of folded cloth. The method is not strictly printing however, as the pattern is not caused by pressure against the block.