The illuminated page: geometry in the frontispiece.

Before the reader reaches a word, a great Qur'an opens on a page of pure geometry. The carpet page, the sunburst shamsa, the gilded border: the illuminators of Cairo, Tabriz and Herat worked the same star constructions as the tile-cutters and the carpenters, in gold leaf and lapis lazuli on paper, at the scale of a hand.

The illuminated Qur'an is the tradition's geometry at its most intimate scale, and its frontispiece, the double page that opens the book before the text begins, is very often a field of star polygons with no text at all. Scholars call this a carpet page, because it covers the sheet edge to edge the way a carpet covers a floor. It was made by a specialist, the mudhahhib, the gilder, working after the calligrapher had finished, with a compass, a ruler and a reed pen, and with pigments that were themselves precious: ultramarine ground from lapis lazuli, gold leaf and powdered shell gold, vermilion from cinnabar, white lead, a little malachite green.

Cairo, Tabriz, Herat

The great age of the geometric frontispiece is the fourteenth century, and its two capitals were Mamluk Cairo and Ilkhanid Iran. In Cairo the seven-volume Qur'an made for the Mamluk emir and briefly sultan Baybars al-Jashnagir in 1304 to 1306, now in the British Library, was illuminated by an artist who signed himself Sandal, largely in gold and blue: its frontispieces are strapwork star polygons in gold outlined against lapis, and the register on this page is drawn after them. The Qur'ans made for Sultan Sha'ban and his mother in the 1360s and 1370s, now mostly in the Egyptian National Library, carry the most elaborate geometric openings the Mamluk workshops produced, with rosettes and interlaces nested inside larger polygonal frames.

In Iran the Ilkhanid ruler Öljeitü commissioned enormous Qur'ans in the first two decades of the fourteenth century, at Mosul, Baghdad and Hamadan, whose frontispieces are among the boldest star fields ever painted, gold and lapis at a scale that fills a page nearly a metre tall. The Timurid workshops of Herat and Shiraz in the fifteenth century refined the tradition toward finer, denser work, and gave the opening of a manuscript its most characteristic Persian form, the shamsa: a single sunburst medallion, a rosette of gold and blue, set alone on the first page, often carrying the name of the patron at its heart.

The same constructions, at the scale of a hand

A carpet page in the Baybars Qur'an and a stone dado in a Cairo mosque of the same decade are drawn from the same star polygons, and the comparison is not a metaphor. The illuminator laid out his page with the same tools as the mason's draughtsman, compass and straightedge, and he used them to construct the same polygons in contact and the same stars from their edge midpoints. The difference is what came after. The mason's lines became the edges of cut stone; the illuminator's became the boundaries between colours. In illumination the polychrome rule of the tile-cutters is followed with pigment: congruent faces take the same colour, touching faces take different colours, gold for one class and lapis for another, vermilion for the small stars between. The studio's class-by-class colouring is that rule, and its illumination register is that palette.

Two things are specific to the page. The first is the frame. A wall pattern runs on until the wall stops; a carpet page is bounded by its border, so that the field is cut by a rectangle and the border is a composition in its own right, ruled fillets of gold and colour and often a running interlace. The studio's composed layouts, the field between friezes and the arched panel, are the same idea: a repeating field, tiling internally, held in a frame that does not repeat. The second is the medallion. A shamsa is a rosette with a centre and a rim, laid out radially rather than on a lattice, and the engine derives it as exactly that, a medallion whose rings grow outward from a central polygon by a proportion the geometry fixes. For a ten-fold shamsa that proportion is the golden ratio.

Gold on blue

The palette of illumination is narrower than that of tile, and it is dominated by two materials that were costly enough to be recorded by weight. Ultramarine, ground from lapis lazuli mined in Badakhshan, gave the deep blue ground; gold, applied as leaf over a size or painted as a powder in gum, gave the line and the principal faces. Where a tiled wall has four glazes, a page often has these two and a sharp accent of vermilion. The result is that the strapwork reads more strongly on the page than on the wall: a gold line on a blue ground is the pattern's skeleton made visible, which is why the line-only register, the interlace drawn as gold wire with the fields left dark, looks so much like a frontispiece.

Where to see it

The British Library's Baybars Qur'an and the Öljeitü Qur'an of 1313 are both digitised page by page. The Chester Beatty in Dublin, the Khalili Collection, the Topkapi Palace Library in Istanbul, the Egyptian National Library in Cairo and the Metropolitan Museum hold frontispieces of the first rank, many online. Read them the way you would read a wall: find the underlying polygons, then the stars, then watch how the border cuts the field.

In the studio

The Illumination Series in the studio's social plates renders eight registers of the page from the engine: the frontispiece seal, the carpet page, the shamsa, gold strapwork on lapis, the seal within the seal, the framed text block, the compound rosette page and the ruled fillets. Every one is a construction this journal derives elsewhere for stone, tile, metal or wood, with the colour set turned to gold leaf, lapis, vermilion and vellum. Derived, not generated.