In her first blog post on the wonders of Polynomial Textual Mapping (PTM) Dinah Eastop used a modern embossed paper seal as an example of the way in which this new technology can literally highlight and capture virtually invisible details on the surface of three-dimensional objects. So what about earlier wax impressions of seals – would PTM help here?
The National Archives holds probably the largest collection of seals in the country. Seals were used in the medieval and early modern period to authenticate documents as well as literally to seal them. They can include portraits of the owner, coats of arms, depictions of animals or buildings and much more, and most also include writing around the circumference (called the legend) identifying the owner. Many of the seals in The National Archives’ collection are fragile, many are small, and some are damaged, and it can sometimes be very hard to see what the seal depicts.
Traditional photography has often struggled to represent seals adequately, because of the need for light and shade to capture the detail on such small and intricate objects. This is especially true for seals depicting heraldry where even a very small difference on one coat of arms might distinguish it (and the seal owner) from another.