The objects and collections we care for can be damaged in many different ways, for example by being mishandled, by being inappropriately stored or they can deteriorate due to their intrinsic composition.
Not only are the causes of damage variable, but so too is the susceptibility of different types of objects to these damaging agents. Stone and ceramics are much better able to withstand environmental fluctuations than organic materials such as wood, paper and textiles; but they may be more vulnerable to poor handling for example through chipping and breaking. Because of these factors the information provided here is only intended as very general guidance. For greater detail on specific types of collections/materials please refer to the ‘Caring for…’ documents or use the Find a conservator pages of this site to locate and consult a professional conservator-restorer.
By understanding the factors that may cause damage to your possessions you can take steps to reduce their impact and thus preserve your collections for the future.
Relative humidity (RH) is a measure of the amount of moisture present in the air. Levels of temperature and RH will vary seasonally, but may also vary within a room. Warm air is capable of holding more moisture so, for example, RH will be higher near to a cool, external wall and this should be considered when deciding where to display or store objects. The appropriate parameters for temperature and RH will vary according to the type of object but in very general terms higher temperatures will result in an increased rate of chemical deterioration of organic objects, and high levels of relative humidity may lead to problems such as mould growth.
One of the most important steps that can be taken is to minimise fluctuations in temperature and relative humidity, particularly over a short time period such as day to night. Organic materials contain moisture and will respond to changes in the moisture content of the surrounding environment by expanding and contracting. This may lead to physical changes such as cracking of wooden objects or cockling of paper. In general terms, try to store items in cool, dry conditions with good air circulation but remember to always seek professional advice for the specific requirements of your possessions or collections.
Light also has the potential to cause great damage, again particularly to organic materials such as paper and textiles. Light damage is cumulative and irreversible and one should avoid displaying vulnerable items such as watercolours in direct sunlight if at all possible. Light can not only cause fading of pigments but can also lead to the breakdown of the materials themselves through photochemical reactions which break down the cellulose molecule leading to embrittlement and sometimes discolouration. Whilst light in the ultra-violet spectrum has the greatest potential to do this type of damage it is also worth thinking about how to display and store objects next to artificial light sources. For example it is advisable not to exhibit works of art close to incandescent bulbs which give off heat.
Pests have great potential to cause damage and can range in size from the destructive furniture beetle (woodworm), to moths and even rodents. One of the most effective measures that can be taken to prevent this type of damage is to display and store your possessions away from food sources. However, it is worth remembering that in many cases your object will be the food source itself and so vigilance is important. In general terms, pests like dark, warm, humid, undisturbed areas so inspect objects regularly, particularly if they are boxed away. Make sure that your possessions are stored in clean locations (dust, dirt and grease also provide a food source) and leave plenty of space around objects so that cleaning can take place without the risk of accidental damage through handling.
Another external source of damage to consider is air pollution. Pollution is damaging to all types of objects – organic materials as well as metals and stone. Sometimes the effects can be minimised by the method of storing an object, for example by framing pictures using good quality archival materials, in other cases one should think about the potential source of pollutants, for example not displaying or storing objects close to where cooking is carried out. This is probably one of the most difficult damaging agents to control, especially for private owners. You should consult a professional conservator-restorer if you think that your collections are particularly at risk from this type of damage.
The materials one uses to store objects can also affect their longevity – in some cases the materials will be found to be the source of damage and so should always be chosen carefully. Again, the combinations of object type and appropriate storage material will vary and one should refer to a professional for specific advice, however it is worth considering the following. Wood, wood products and many paper products made from wood contain harmful acids which can accelerate damage and staining, for example acidic mounts may cause discolouration of works of art on paper. For paper and some textiles one should therefore consider using acid free products. These products can be ‘buffered’ (containing an alkaline reserve e.g. calcium carbonate) or un-buffered. Paper objects are often best stored in ‘buffered’ materials, whilst others that are naturally acidic such as wool, silk, leather and photographs may be better suited by un-buffered products (pH neutral). If you are in any doubt, always consult a professional conservator-restorer.
Be careful about using plastic sleeves to store items. Whilst this can be an effective method of minimising damage through handling you need to use inert products that will not deteriorate over time such as an inert polyester. Boxes are another good method of minimising damage – both by protecting an object from physical damage, but also by minimising the exposure of an item to environmental fluctuations. However, the boxing materials should be carefully selected and it is extremely important to regularly inspect boxed items for any signs of damage, for example by pests.
The information above is intended as a very general introduction to the issues associated with the storage of objects and collections. For more detailed guidance you are always advised to consult a professional conservator-restorer.
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© Icon, the Institute of Conservation 2006.
This article offers general guidance and is not intended to be a substitute for the professional advice of an accredited conservator. The views expressed are those of the author or authors, and do not necessarily represent the views of the Institute of Conservation. The Institute of Conservation and its partners accept no liability for any loss or damage which may arise if this guidance is followed.