The study of seals, sigillography or sphragistic (s) was originally a branch of diplomatics, with which it still shares much of its subject matter, though the sigillographer's approach is primarily technical and archaeological.
Sealing, as a means of authenticating written matter, has been practiced from remotest antiquity: in western Europe it enjoyed its greatest vogue between the 12th and the 15th century, when the principals in most transactions could not (or at least did not) validate their acts by signature. During this period seal owners were to be found at every level of society, and the great had needs and functions for which one seal might be insufficient.
The matrix by means of which the seal impression was made was most commonly metal: latten, a brasslike alloy, was normal, with precious metals used by the rich and lead by the poor. Jet, engraved gems (often survivals from classical antiquity specially mounted in metal), ivory, bone, and even wood were also used. The device and its circumambient legend were incised in reverse on the matrix, the back of which (on a single-sided seal) was shaped to form a handle, with or without a ring. The matrices of a double-sided seal were flat slabs, sometimes hinged but oftener having projecting pierced lugs through which pins were passed vertically to secure correct register.
In the papal Curia (imitated in this respect by some other Mediterranean chanceries) the impression took the form of a bulla, a ball of lead squeezed flat between two matrices. So-called bulls of gold and silver, used for documents of exceptional ceremoniousness, are seldom or never true seals; when they are not casts, they consist of thin leaves of metal stamped in shallow relief and soldered together. But the overwhelming majority of surviving medieval seal-impressions are in a material normally composed of roughly two parts of beeswax to one of resin. Chalk or ashes might be added to this mixture to harden it and to combat warmth later. Apart from white, which occurs before 1100, red and green were the earliest and the commonest variations on the natural color of this compound; but black, brown, and (rarely) blue are also found. Impressions in natural wax were sometimes coated with a dark varnish. Colors were occasionally combined in a single seal, as when the impression is borne on a layer of wax set in a "saucer" of wax of another color. There may be significance in the color used; for example, in both England and France royal grants in perpetuity were sealed in green.
The commonest shapes for medieval seals are the circle and the oval, the latter frequently pointed at top and bottom and especially affected by ladies and ecclesiastics, who were conventionally portrayed on their seals in a standing position. Other shapes are rare: even the "Gothic shield," which lent itself to the much-favored armorial device, is seldom found.
Within any one country the great seal (or seal of majesty) of the sovereign tends to be at any given time preeminent in size and to grow progressively larger, reaching a diameter of about 4½ inches in France at the end of the 15th century; the seals of subjects were ordinarily much smaller. Privy or "secret" seals were smaller still; they were used either to warrant the employment of the owner's great seal or to make a counter-impression in the back of a single-faced great seal and thus identify the seal owner personally with his act.
The devices on medieval seals are so diverse that the most thorough classification leaves a large category of "arbitrary" or "miscellaneous" charges outside the more readily defined types, such as the enthroned monarch, the patron saint, the mounted knight, the standing figure, the coat of arms, or the stylized castle. But all alike provide a rich source for the study of medieval art in general.
Legends, usually in Latin but occasionally in the vernacular, run clockwise around the circumference from a point right of top center. They generally proclaim the ownership and nature of the seal in formal language, but allusive, punning, and pious mottoes may also be found. The lettering develops from crude Roman capitals to "Lombardic" in the late 12th century and from Lombardic to "black letter" about 200 years later.
Wax seals might be applied directly to the surface of the document, which was often prepared by incisions or other means of fully engaging wax and parchment. Applied seals of the 15th century are frequently covered by a layer of paper interposed between matrix and wax at the moment of sealing. Bullae and double-sided wax seals were necessarily pendent. They hung either on a tongue, provided by almost severing the bottom margin of the document, or on tags, strings, or laces passed through slits or holes in the margin. The papal bulla was borne on hempen strings on letters of justice and by silk on letters of grace. Pendent wax seals are sometimes protected by woven bags or small boxes of wood or metal known as skippets.
Bibliography: h. jenkinson, Guide to Seals in the Public Record Office (London 1954). j. h. roman, Manuel de sigillographie française (Paris 1912). h. bresslau, Handbuch der Urkundenlehre für Deutschland und Italien, ed. h. w. klewitz, 2 v. (2d ed. Leipzig 1912–31) v. 2. a. de boÜard, Manuel de diplomatique française et pontificale (Paris 1929) 333–351, an admirably clear and concise summary. m. tourneur-nicodÈme, Bibliographie générale de la sigillographie (Besançon 1933), for sigillographic works pub. in Europe, particularly strong on the copious French literature. y. metman, in L'Histoire et ses méthodes, ed. c. samaran (Paris 1961) 393–446.
[l. c. hector]