This 17th century portolan chart came in this summer from the Museum of the Order of St John. It’s an interesting one, I think bound at a later date (or at least not part of its original making) into boards, à la portfolios, so that it had a tooled red leather covering, and the two boards opened with the chart as the “pastedown” on the inside. The right board, and therefore right half of the chart, aren’t in the collection.
The chart belongs to the end of the great tradition of portolan chart making that began in the late 13th century. The western half of a portolan chart of the Mediterranean from the Marseilles school of chart makers; see the charts of Francois Ollive (c.1644 - 1664). Nicolai il ? was probably a colleague or pupil of Ollive. This late Marseilles chart was probably made as a presentation copy to a noble or merchant of Marseilles; it is more highly decorated than a mariner's portolan chart. The island of Malta bears the Order's cross; if we had the eastern half we should probably find Rhodes changed in a similar manner.
The chart had been on display for many years and the curator was keen to address the resulting damage before putting it back in storage for protection. The top, bottom, and left edges of the chart are in good condition; the turn-ins protect the edges of the board and keep all the materials adhered well. However, the split spine edge, now the right side, is open, which has allowed it to distort.
Parchment is a skin stretched and dried under tension, and responds dramatically to fluctuations in temperature and humidity—take a skin from a humid environment to a dry one or visa-versa and you can almost watch it move before your eyes. All skin, leather included, also experiences a shrinkage effect when exposed to heat and humidity: if you put a piece of skin in water, and heat it up, at a certain temperature (depending on the type of skin and the way it was processed) it will shrink. When leather and parchment get old and damaged, that shrinkage temperature lowers. Ambient temperature and humidity could be enough to facilitate some shrinking of the material.
The problem with the warped boards and separated parchment is threefold: first, the damage is likely to get worse, which will eventually stress and split the turn-ins and cause further separation of the materials towards the left edge of the chart. Second, movement in the parchment isn’t good for the thickly-applied media, which already shows cracks and some losses. It appears well-adhered, but movement of the substrate could threaten that. Third, as indicated by the arrows in the image below, the uneven surface has led to some abrasion of the skin in particular areas.
It’s currently under weight; my approach to flattening has been very light weight increasing over a period of several months until it’s flat. I’ll then work on securing the edge so it’s less vulnerable, and packing the too-large box it’s currently housed in so that it will protect the chart better—stay tuned.