Conservation Guidelines

Concerning the transport of manuscripts, see the Guidelines (in German) by Martin Strebel and Rafael Schwemmer. 

Before digitization begins, the condition of each manuscript is evaluated and a restoration specialist is consulted if necessary. The digitization process follows a strict set of procedures that has been periodically reassessed and improved since the project began.  

During the digitization process, the manuscripts must be protected against wear and tear in order to ensure that handling stresses are less than those experienced during an average use of the manuscript in the reading room or during an exhibition. All external conditions influencing the manuscript are regularly checked.

The digitization of each item must follow clearly defined criteria:

  • manuscripts shall be held in a climate-controlled area, so that there is only a minimal difference between the temperature and relative humidity in the holding area and in the digitization area
  • minimal manipulation of the manuscript itself, except as required for actual page turning; that is, no pushing back and forth, no turning over or flipping of the item
  • the angle at which the bound book or the cover itself is opened may in no case exceed 140°
  • no mechanical pressure shall be used to flatten the pages, such as with a glass plate. Page flattening may be achieved by the application of a gentle vacuum from below
  • relative humidity in manuscript areas shall remain between 40% and 60%
  • the temperature in holding and digitization areas shall remain between 18° und 25°
  • no manuscript shall ever be left unattended in the studio, and all manuscripts shall be locked in the safe at the end of the work day.

Flash or Continuous Lighting?

Flash lighting for digitization photography has become the preferred overall practice among Swiss libraries in recent years. This method is recommended not only by the superior quality of the images produced, but also, more importantly, by conservation considerations:

  • The possible damage produced by any type of light to any lit object is based on a combination of the quantity of light (H), the light strength (lx), and the duration of light exposure (t). The “reciprocity principle” has been scientifically proven to apply to flash lighting. In other words, light exposure at 20,000 lx (daylight or flash apparatus) for 1/4,000 of a second (average flash duration) is equal to exposure at 50 lx (dimmed room lighting) during 1/10 second.
  • Ultraviolet exposure can be practically neglected with the use of flash lighting.
  • Flash lighting produces much less heat than studio lamp lighting.

Digitizing with the Mobile Camera Table

In exceptional cases a manuscript may be digitized on site using a mobile photography table („Traveller TCCS 4232“). On-site digitization is not recommended from a conservation point of view, as conditions in either of the digitization studios produce much higher quality images and ensure gentler handling techniques.