Paper became the most important carrier of text in the fifteenth century. Other than on parchment which had been used for centuries, more and more was written on paper and without paper the mass production of books following the invention of printing in about 1455 would not have been possible. The first dated printed books in the Low Countries appeared in 1473 in Alost and in Utrecht, partly preceded by some undated editions of Dutch prototypography.

Hand-made paper was produced from rags. To process these into pulp, clean water and energy were required supplied by paper mills (water mills and later windmills). The sheets were produced with moulds, couched, dried, sized and polished.

No paper was made in the Netherlands until 1585 and it was limited to such an extent in Belgium that nearly all paper for printing in the Low Countries had to be imported. With a few exceptions (Germany and Italy), it came from North-East France: Alsace, Vosges, Lorraine, Burgundy and Champagne with Troyes as its most important centre.

Hardly any data have been published on the purchases of paper by incunabula printers from the Netherlands. Archival records are available for sixteenth-century purchases of paper by Plantin's printing office (between 1563 and 1589) from traders in Antwerp, Troyes and also in Paris, Rouen and La Rochelle. In the archives of Antwerp, Lode Van den Branden, while researching the Antwerp book trade in the fifteenth and sixteenth centuries, found sixty names with notes on paper manufacturers and paper traders.

Types of paper are identified by the dimensions of the hand-made sheet and by the watermark. The usual sizes in the fifteenth and sixteenth centuries for the sheets were mostly: Imperial c. 49x74 cm; Royal c. 43x62 cm; Median c. 35x51 cm; Chancery circa 32x45 cm.

Of the two thousand incunabula printed in the Netherlands on paper, only three editions were printed on Median paper and twelve on Royal paper. The rest was printed on the smaller Chancery paper.

The most important distinguishing feature of paper is the watermark. Almost without exception, all paper used in these regions had a watermark; in the vast majority of incunabula from the Netherlands the Gothic letter 'p' in many variations. In paper from the sixteenth century the watermarks were regularly accompanied by the names or initials of the paper manufacturers.

During this period all paper was produced with two moulds, and paper stocks can be distinguished by two watermarks which were very like one another, but which are differentiated by their position in either the left or the right side of the mould.

Watermarks can be reproduced using tracings or, even better, by rubbings, beta-radiography or electron radiography which make identification and dating possible. As incunabula in particular are often undated, paper research, after typeface research, is certainly worth the effort. When the same paper has been used in both undated and dated editions, they can be dated correspondingly.