Previous
Next
Seal construction methods
Seal construction methods
Constructing a seal, in other words making the impression, is the key moment in the lengthy preparation of documents issued by chanceries.
Applied wax seals were attached after the writing support had been scraped down to make it rough and thus enable durable adherence of the seal. In other cases the wax was poured into cuts or slits, at times intersected, that had been scored in the writing support to provide a stable base for the seal. Some chanceries placed a mesh of thin parchment strips or twine between these cuts and the wax in order to further reinforce the area.
Papered seals were impressed by placing a layer of paper, usually a lozenge or a square, between the hot wax and the matrix; the same procedure was used for paper.
Pendent impressions were fashioned by inserting the appendage system in a fold, called plica, at the bottom of the writing support. This fold reinforced the area of the document the seal was suspended from, and two or more holes called oculi were pierced through the fold to insert the cord attached to the seal. The appending element was then knotted under the plica and the other end incorporated in the softened wax that was ready to be impressed by the matrix. In many cases the imprinted wax layer was set in a small protective wax shell with rounded back and high sides called culla. In addition to the wax culla, seals were sometimes placed inprotective wooden or metal skippets that had been pierced to accommodate the cords before the wax impressions were made.
The use of tin skippets in the thirteenth century and the later use of wooden ones, at times with lids, in the following centuries underline the growing desire to protect seals. Extraordinary examples of skippets produced in precious metals, such as brass, gold, silver and ivory, were created during the Renaissance.
Lead bulls were fashioned by making a metal sphere with a hole through the centre for the cord. The bull was then pressed between two matrices (recto and verso) engraved with iconographic devices.
The tools used to strike bulls changed over time. The first was a mobile coin die carrying the matrix that was struck on an anvil by a hammer. Then the so-called boulloterion, a plier-shaped instrument with two matrices at its ends, was developed to stop the metal sphere slipping when it was struck. Subsequently more complex methods were developed. Very large presses exerting gradual pressure were used to imprint the devices on the metal and speeded up the sealing process.
The importance of gold seals called for different construction techniques. The very few solid gold seals were created in the same way as lead ones. Most gold seals are made of two thin sheets impressed at different times and then joined by special processes. The edges of one sheet could be directly bent over the other, or they could be positioned on a circular separator. When the sheets were thick enough they were either soldered together or onto a strip, and in some cases the two sides formed a real and proper box that could be locked by pressing. Some documents reveal that during the Renaissance seals were created using the same casting and chiselling processes employed to make the matrices, but obviously the final result was in relief.
Articles
