Damage prevention

Sound housekeeping plays an essential role in preventing damage to books and the covering material used in their bindings and is therefore an important part of conservation. Material care relates not only to the way books are stored - lying or standing, in steel or wooden bookcases, in boxes or not - but also to the control of environmental factors. Many publications dealing with material care have appeared in recent years. This chapter only deals very briefly with a limited number of aspects: book handling, bookcases, storage material, shelfmarks, climate control, lighting and exhibitions. Many useful publications on this subject can be found e.g. in the Art and Archaeology Technical Abstracts (AATA), the Conservation Information Network (CIN) database and by the Website of Conservation OnLine (CoOL).

Handling

It is a widely known fact, but cannot be emphasised enough: the greatest threat to the book is its user. Careless handling of (old) books in particular can cause a lot of damage.

Removing books from the bookshelf
Incorrect removal of books from the bookshelf can cause much damage to the spine. Never remove a book from the bookshelf by the headcap: headband, headcap, and spine are all liable to tear. Also avoid pulling the book from the shelf by its spine using your fingernails as this may cause scratches to the covering material. If there is enough room above the book, stretch your hand over the book and slide it forwards a little so that you can grasp it securely while removing it from the shelf. If there is not enough room above the book, you should push adjacent books back a little, thus creating enough room to allow you to grasp the middle book securely. Try to avoid tilting the book as this may result in damage to the bottom headcap and headband.

Opening and consulting
Books can also be damaged when they are opened. Books are often pressed wide open, even when the binding (obviously) does not allow this. This can cause fragments of the leather or parchment spine to break off and may even result in the whole spine becoming detached from the text block. The best way to open old books is to place them spine down on a flat table and then to open the text block in the middle and allow the two equal parts to subside slowly onto the table. Opening the book this way makes it easy to search for the required page and exerts a minimum of pressure on the spine and hinges. If the binding construction does not allow the book to lie easily in a horizontal position, it should be consulted on a 'book support', a kind of table-top lectern that allows the book to lie open in a slight V-form. Such a support can be made from felt-clad wood or synthetic plate material (perspex). It is important for the support to have more than one position, so that if a page at the beginning of the book is being consulted for instance, the support is higher for the front than for the back. It goes without saying that the support should have no sharp edges that could damage the binding. A book support can also consist of wedge-shaped and rectangular pieces of foam rubber (polyether), which can support the book in a variety of positions. With the help of additional accessories it is even possible to support the spine of the book. A 'book pillow', made of soft material filled with tiny polystyrene balls, can also come in handy here. It provides good support for a range of positions. The advantage of these last two supports is that they are soft and do not damage the covering material of the bookbinding.
To save readers from having to keep their hand continuously on the page being studied (and thereby thumbing the page) a weighted cord can be used. This consists of a chain of small lead pellets covered with cloth and sufficiently heavy to hold down the page. As well as preventing damage to books, such a reading aid also makes the users aware of the book's vulnerability and usually results in their being more careful with the book.
Since grasping certain kinds of leather such as suede and natural sheep or calfskin with bare hands can cause stains or other forms of damage, the use of cotton gloves is recommended. Some forms of damage (e.g. red rot or the effects of leather marbling) are better not touched with bare hands. Vinyl or latex gloves are the best option in this case (loose particles tend to adhere to cotton gloves). In the case of highly vulnerable bookbinding material a dust-jacket made of a special kind of polyester foil (such as melinex) can be very useful.

Photocopying
Most photocopying machines require books to be opened completely and placed face down on the glass plate, a procedure that can cause great damage to the binding construction. Another danger posed by photocopiers is the large dose of UV radiation, especially in the case of (often old) xenon copiers. Despite the risk to (old) books, copies often have to be made in institutions. The risk of damage can be lessened by using special photocopiers where the book can be copied while lying in V-form. There are also photocopiers where one half of the opened book (up to the middle fold) can hang down at an angle of 90º beside the machine. The disadvantage of these copiers is that the book has to be lifted and turned every time a new page is selected for copying, while the side of the book hanging beside the machine is unsupported. Damage can be minimised if the copier is operated only by expert personnel.
Nowadays there are also book-friendly scanners on the market, which allow scanning per page. They are supplied with a 'book cradle' which holds the book without putting any pressure on the binding.
The detrimental UV radiation from photocopiers can be restricted by opting for a halogen or mercury fluorescence copier. These machines release far less UV radiation than xenon copiers.

Bookcases
Avoid placing bookcases immediately against an outer wall where there is a greater risk of condensation and consequent fungal growth. If lack of space requires the use of compact bookcases, make sure that ventilation is possible, even when the bookcases are completely pushed together. Unfortunately many compact case systems tend to vibrate when moved, which may result in a book being shaken off its rack and getting wedged between the cases. This can lead to serious damage.
There are advantages and disadvantages attached to both wooden and metal cases. In general, wooden cases have a stabilising effect on humidity in the room. Then again, there are a number of clear disadvantages: various kinds of wood, for instance oak, secrete acids and other detrimental substances and cannot therefore be recommended. If wooden cases are chosen, the wood should always be finished with lacquer or a coating. Polyurethane lacquer on a water basis is recommended; after the lacquer has been applied the solvent should be left to evaporate for at least three weeks. Steel cases may rust if the finishing layer is damaged, which may cause stains and damage on bookbindings. Steel cases are therefore best treated with a chemically stable 'powder coating'. ('Storage furniture: a brief review of current options', in: Preservation of Library & archival materials: a Manual, Northeast Document Conservation Center - Technical Leaflet, Storage and Handling, 1994) Contrary to what is generally thought, steel cases are an even greater hazard in the case of a fire than wooden ones. They may not burn, but they do distort in intense heat which may result in (part of) the cases falling over and the books ending up in the aisles and in the water used for fire extinction. Both wooden and metal cases should, of course, be neatly finished and have no projecting screws, nuts or sharp edges that might damage the books.
Bear the following recommendations in mind when placing books in a bookcase:

  • Normal sized books are best placed so that they stand on the tail edge; never place them fore edge down: in this position the weight of the text block may pull on the spine, distorting it and even causing it to come away from the binding.
  • Do not arrange the books so tightly that they are difficult to remove. Tight placement can result in damage to the binding (e.g. torn headcaps or spine covers) as the books are being taken off the shelf. Nor is loose placement a good idea: books lean at all angles, thereby increasing the risk of damage to bindings or endpaper constructions. If there is room left over on a shelf, use a bookend to keep the books standing upright.
  • Keep books of the same size as much as possible together as this makes them less susceptible to dust. It has also been found that books arranged according to size suffer less water damage in the event of leakage.
  • Small books - especially in moving compact bookcases - are liable to slide off shelves. Damage can be prevented by storing several such books a small card-board tray.
  • Large and heavy books should be stored on the lower shelves so that they do not need to be lifted above head height, with all the risks that entails.
  • Very large books should be stored horizontally, but never more than three on top of one another.
  • Leather with a pulverised grain can cause stains; take care not to put such bindings next to paper or cloth bindings. Acids and fats can also migrate from the leather to paper or linen. This can be prevented by using a polyester dust jacket.
  • Desiccation sometimes causes concave warping in parchment-covered boards with the result that the book starts 'to work its way out of the row'. Not only may such a protruding book eventually drop off the shelf, but it is also more susceptible to dust. The best way of storing these bindings is in 'book shoes'.

Storage materials
Boxes and slipcases can contribute greatly to the preservation of bookbinding materials. This is especially important in collections which contain a lot of bindings with bosses or chains. Although these metal parts were originally attached to bookbindings to protect the book - against damage as well as theft - they can cause a lot of damage to neighbouring books. The same applies to metal clasps.
Closed boxes not only limit physical damage, but also serve as a buffer against the effects of detrimental air pollutants. A closed box also provides good protection during the transport of a book being loaned out for exhibition. Boxes and slipcases may be equipped with a support for the text block so that - especially for large, heavy books - distortion of the spine can be prevented. An hermetically closed box may give rise to a microclimate so that condensation forms in response to changing climatic conditions. For this reason it is necessary to make an opening, a round hole for instance, in such boxes.
Avoid using brightly coloured linen or marbled paper to cover boxes and slipcases. Most of these are not colourfast and may cause extra damage, for example, in the event of leakage.

Double tray boxes
The double tray box is a completely closed box which can be used to store the book - standing or lying - and which protects against bumping and external influences such as light and dust. The box consists of three separate parts - box, lid and back - which are joined by hinges. Provision may also be made for a book chain. A double tray box is also an excellent form of protection for the book during transport, provided the book is not able to move inside the box.

Slipcase
A slipcase protects all sides of the book except the spine. It is suitable for protecting book-bindings placed in a museum display. One major disadvantage is that the spine discolours more than the covers, but then this also applies to books stored unprotected in a bookcase (see also: Lighting). Another disadvantage is that it is not always easy to get the book out of the slipcase. Semi-circular notches on the sides for thumb and index finger can solve this problem.

Book shoe
A book shoe is a kind of slipcase which leaves both the spine and the head edge uncovered (drawing 9). At the bottom of the shoe is a support for the text block. This is especially useful for large, thick books with overhanging sides where there is a tendency for the text block to sag forward, pulling the spine with it and causing tension on the shoulder, which may even end up tearing. This problem can be prevented by the book shoe, which also closes the book neatly so that no dust can penetrate the text block. An additional advantage of the book shoe is that it prevents the bindings from being damaged by any clasps and/or bosses of adjacent books. The fact that the book is not completely closed off from the environment entails several advantages. To begin with there is no risk of a dangerous microclimate developing. Secondly, the spine and any title can be recognised at once, which makes the book shoe suitable for museum display. Thirdly, the book is easily removed from the book shoe, unlike the slipcase where a book may jam. And, last but not least, a book shoe is fairly simple and cheap to make compared with a double tray box or slipcase.

- Klik voor een uitvergroting
Drawing 9 The book shoe


Phase box
A phase box consists of two strips of strong, medium thick, acid-free cardboard (e.g. 425g/m²). One strip is machine-direction cardboard and measuring exactly the width of the book. The other is cross-direction cardboard and measuring exactly the height of the book. These two strips are glued together at right angles in the middle (drawing 10a). Then the projecting sides are folded parallel to the glued rectangle. The projecting parts can be folded around the book. The phase box is kept closed by a thin piece of string wound around the box and fastened at the front around a button (drawing 10b). A phase box can be made for (vulnerable) books but also for loose-leaf material. Although not as sturdy as a double tray box, it is a good and inexpen-sive alternative, certainly as a temporary measure.

- Klik voor een uitvergroting
Drawing 10 Phase box



Shelf-marks
Library books are placed in bookcases according to a particular (shelf-mark) system, which is usually made visible by numbers and/or letters on the spines. If self-adhesive synthetic tapes and stickers are used, the attachment between adhesive and carrier (sticker) is likely to give way. Tapes or stickers fall off the spine leaving the adhesive behind, as an irremovable, sometimes sticky, brown contamination on the material of the spine.
One should therefore, certainly for older collections, never use self-adhesive tapes or stickers, but acid-free, non-gummed paper strips, ovals or rounds. The best way to affix them on leather or parchment is by using thick paste. It is not advisable to paste shelf-marks on important and/or valuable bindings. In these cases it is better to opt for a system of numbers on acid-free cards/strips which can be inserted between the leaves of the text block so that the shelf-mark sticks out above the head edge.

Climate control
In libraries, archives and museums, the word climate refers to indoor climate. Leather, parchment and paper respond to humidity, temperature and light. Too much humidity causes the material to expand, too little causes shrinkage. Humidity, combined with heat, can also lead to fungal growth. Excessively high temperatures will dry out the material. Light degrades the binding material and causes discoloration.
Advisory guidelines for relative humidity and temperature in storage rooms containing archival materials have now been formulated. This advice was drawn up with the aim of arriving at 'a responsible conservation of cultural heritage at a reasonable cost in terms of investment, exploitation and maintenance'. (Adviesrichtlijn luchtkwaliteit archieven. 's-Gravenhage, Rijksgebouwendienst (RGD), 1995. The report was drawn up within the framework of the Delta Plan for the Preservation of the Cultural Heritage in the Netherlands.) The same guidelines can be used for library material.
The recommended temperature for storage rooms is 18 °C (± 2 °C). The recommended relative humidity (RH) for storage rooms is 50% (± 5%). (RH should always be considered in relation to temperature: relative humidity is the proportion of actual moisture to the maximum possible amount of moisture in the air at a specified temperature.)
Parchment material, if stored separately: 18 °C ±2 °C, RH 50% ± 5%; winter setting: 16 °C, 45%; summer setting: 20 °C, 55%.
The Advisory Guidelines also provide data on air quality levels one should strive for during airconditioning, especially with respect to ventilation.

Lighting
Light - the part of the electromagnetic spectrum visible to the human eye - accelerates the degradation of all natural polymers of which books are composed. Light may cause colours to fade and paper to become brittle and yellow. From a preservation point of view, therefore, one should avoid exposing books to light as much as possible. In practice this will always come down to a compromise between making objects visible and the possibility of light-induced damage. But daylight, in addition to visible light, also comprises invisible ultraviolet and infra-red radiation, both of which may cause damage to books.

  • (Invisible) ultraviolet radiation (UV) has a wavelength between 100-400 nm
  • Visible light has a wavelength between 400-760 nm
  • (Invisible) infra-red radiation (IR) has a wavelength longer than 760 nm

Of the three, UV radiation has the highest energy level and is therefore the most damaging. This is the radiation that causes decomposition in the type of organic material found in bookbindings such as protein chains (leather, parchment), dyes and pigments, binding agents and adhesives. Measurements have shown that damage can be reduced by about 60% if UV light is filtered out of the daylight. It is therefore recommended that the UV component of light be eliminated. This can be done by placing UV-absorbent glass, foil, acrylic plate, etc., between the light source and the object, but it is even better to eliminate daylight altogether with curtains or some other form of shuttering and to work with artificial, low-UV light.
The light from incandescent and halogen light bulbs is naturally low in UV radiation but on the other hand they produce rather a lot of infra-red light in the form of heat, which is also detrimental. This damage, caused by heat-induced changes in the humidity levels of the objects, is mostly physico-mechanical such as - in the case of leather - a gradual increase in cracks in the leather fibres and a loosening of the grain. Fluorescent lighting has a relatively high UV rating but fortunately there are also low-UV strip lights on the market. Other factors affecting the severity of damage are the luminous intensity (flux) of the light source (quantity of light radiated as expressed in lumen) and the duration of lighting. The higher a lamp's wattage, the more lumen it radiates. The exposure time determines the amount of damage: double the length of exposure and you double the damage. A simple way of limiting damage in storage rooms is to install time switches that turn the light off after a fixed interval.

Exhibition
Exhibiting books requires special care and expertise. Damage may occur when glass plates are used to exhibit open books. Not only can this destroy the binding construction but it can also strain the leather or parchment so that it tears - usually at the hinge point. It is therefore important that books that do not fall open easily, should be opened only to the point at which they begin to resist. They should then be tied up in this position using strips of polyester foil, and placed - supported - on a perspex stand. Thus exhibited, the covering material is not exposed to tension and no damage will occur.
During exhibitions, books displayed both inside and outside showcases are liable to damage from light and other environmental factors. Damage from UV radiation can be prevented by using light sources with a low UV rating (see also: 'Lighting'). Incoming sunlight must be screened by curtains, UV-excluding foil or some other type of sun excluder. The illumination level is easily measured with a lux meter. International guidelines recommend a maximum of 50 lux (lumen per square metre) for books and other vulnerable material that are permanently lit. Short exhibition periods are, of course, to be preferred. As an extra preventive measure one could install time-lapse light switches that must be activated by visitors.
Climatological conditions are more difficult to control in an exhibition space than in a storage room. One should at any rate try to establish a constant temperature and humidity that is acceptable for both visitors and books. The following values are recommended: maximum temperature 22 °C, maximum RH 60%. Thermohygrographs or other climate recorders can be placed in the showcases for purposes of control.To keep the temperature in the showcase low, light sources should be placed not in the case itself but in a separate hood with its own ventilation, above the showcase. Note that damage can also be caused by fumes from noxious substances (such as acids) given off by wooden showcases, especially oak.
Parchment bindings in particular require a constant RH. If this is not provided, the bindings are liable to warp irrevocably and/or tear at the joints. It is even possible that the slips of the 'laced-in thong' may pull through the binding if the RH is too low. If there is no climate control system in the exhibition room, it is better not to exhibit books, or to work with portable humidifiers and dehumidifiers. Long-term exhibition of leather and parchment bookbindings is not recommended. Dismantling a book exhibition requires special care. Leather and parchment bindings that have been exhibited for a long period of time in an open position may be difficult to close and forcing them may result in the covering material tearing at the hinge point. The best approach is to try moving the opened cover carefully to and fro a number of times; each time it will close a little further.
Cotton gloves should be worn when tying up easily soiled books (suede or natural calfskin) and placing them in or taking them out of a showcase. This avoids stains that can be caused by acid or fat in the skin.
When books with leather or parchment bindings are transported they should be given additional protection, for instance by wrapping them in plastic bubble wrap. Books with clasps, bosses and chains require extra care. It is inadvisable to transport bindings affected by 'red rot' or leather marbling.

Literature


Clarkson, C., 'The Book Shoe', in: The Abbey Newsletter, 12 (1988), 3, pp. 47-48.
Ekkart, R.E.O., 'Het tentoonstellen en hanteren van boeken', in: CL-themadag, no. 10, Amsterdam, 1986.
Lanting, R.W., Preventieve maatregelen tot behoud van archivalia en boeken. Luchtverontreiniging. Delft, 1990. (TNO publication no. P89/075a).
Lodewijks, J., 'The Influence of Light on Museum Objects', in: Recent Advances in Conservation, IIC, Rome, 1961.
Roelofs, W.G.T. and Hofenk de Graaff, J.H., 'Onderzoek naar de veroudering van papier in stapels', in: Onderzoek naar de mogelijkheid archiefmateriaal, boeken en andere voorwerpen van culturele waarde te beschermen tegen luchtverontreiniging door het gebruik van gebufferde dozen en omslagen, Amsterdam, Centraal Laboratorium voor Onderzoek van Voorwerpen van Kunst en Wetenschap, 1994. (CL. Project no. 92/192).