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Conservation of Natural History Specimens

By Robert Entwistle, Jeanette Pearson, Peter Winsor and Stephen Ball

Natural history specimens were once an essential part of all general museum collections. Indeed, many museums were founded on them as manifestations of the Victorian desire to classify and apply systematic nomenclature to the natural world. Until relatively recent times, for most visitors, the museum experience meant rooms filled with minutely labelled animals and birds, and sometimes a diorama or group depicting a particular habitat or a dramatic scene from nature, suitably red in tooth and claw. Specimens, often in the form of game trophies, were a commonplace in country houses too.

Now, changing attitudes and legislation have demoted natural history collections from their former prominence in main display areas to the oblivion of long-term storage, disposal or even destruction. Some specimens have resurfaced as 'decorators' pieces', whose survival depends on the vagaries of domestic fashion. Meanwhile, in museums the 'natural world' is now largely represented by fields such as geology, or in its human manifestations through archaeology and ethnography.

Present unease about the origins of natural history specimens is understandable, and it is no longer possible to produce the kind of collection that could be created by field trips in 1890, 1920 or even in 1960. But this must not overshadow the exceptional importance of those specimens that still remain in museum or private collections.

Why conserve natural history specimens?

Most specimens are now literally irreplaceable, or have a high rarity value. Some species are already extinct, with more under threat or nearing extinction, and there is now legal protection at national and international levels as well as a new attitude to wildlife and habitat conservation.

Many mounted specimens were prepared by noted taxidermists of the past, such as Rowland Ward, and are valuable works of art in their own right. Taxidermy is a skilled profession; specimens are expensive to prepare and mount and should be treated with respect. They may be just as valuable as the painting on the wall or the vase in the case.

As well as the more obvious mounted specimens and dioramas, less showy collections housed in drawers and cabinets are still extremely valuable as scientific records in their own right, and have importance as indicators of previous cultural and scientific attitudes and past 'lifestyles'. For example, ornithologists and wildlife artists can acquire knowledge from scientific collections of birds' eggs or skins that would otherwise be almost impossible to obtain.

Storage and Display: Maintaining a Suitable Environment

Specimens in museums and private collections come in a variety of forms. Mammals and reptiles often appear as full specimens, but many mammals are preserved as mounted heads, especially in the form of game trophies in private hands. Birds, fish and reptiles normally appear as full specimens, though some scientific or other systematic collections may consist of skins, skeletons or other unmounted elements.

Many whole specimens are displayed in fully or partly glazed cases, or form part of a diorama created by the taxidermist or past museum staff. Wall mounting is a favourite method of presentation for fish. Drawers or cabinets are often used to house collections of smaller items - but make sure that collection care procedures do not harm such cabinets, which may be specially constructed or contemporary items of furniture of considerable intrinsic value.

Natural history specimens require the normal high degree of care regarding temperature, humidity and light levels. This aspect of conservation should be routine in the museum environment, but may be less easy to promote in private houses and similar environments. In general, specimens are best displayed in a cool area, away from damp and out of direct light.

A damp environment, particularly when associated with warmth, creates conditions that favour chemical decomposition, mould formation and pest attack (see below). High temperatures coupled with low humidity - such as may exist near a radiator or boiler - may cause skin to shrink and tear. Mounted specimens should never be placed on a wall over an active fireplace that is also producing soot and other harmful emissions.

Strong light sources will cause fading, so avoid direct sunlight - say, on a specimen sited in a window or under a skylight - and spotlights. Try to reduce both the period and the intensity of light falling on the specimen. Ultraviolet light can be reduced by suitable filters, though these need periodic checks because their efficiency declines with time.

Cleaning and Minor Repairs

Careful, planned cleaning is a necessary component of good conservation practice, but conservation and taxidermy are specialised skills. If you decide to attempt minor repairs, remember that it is very easy to damage a specimen, leading to expensive conservation and restoration and in extreme cases total loss. If in doubt, always seek qualified advice. For example, torn skin must be relaxed by a natural history conservator or a qualified taxidermist before it can be repaired.

Inspection is the first stage of any cleaning programme. Before attempting to clean any specimen, thoroughly check it to see that it is sound. Are the hair and feathers on mounted specimens secure? Are there loose scales on fish or reptiles? Wet cleaning is sometimes ill advised (see below); even where it is relatively safe always test an unobtrusive but representative area of the specimen with a damp cotton wool bud.

Mammals

Mammals can be cleaned using a vacuum cleaner at its lowest power setting; fit a piece of gauze or muslin across the nozzle to guard against loss of fibres. Then run damp cotton wool pads over the surface and immediately dry the area with tissues or dry cotton wool. Caution: only dampen the fibres; do not wet the skin, which can cause it to stretch and disfigure.

After wet cleaning, gently brush the hair or fur in the direction of growth with an appropriately sized brush (such as an animal grooming brush or old hairbrush). This stops the fibres from matting. The specimen should be allowed to dry in a cool draught of air. You may also use a hair drier on a cold, gentle setting, which provides an opportunity to fluff and rearrange the hair or fur back into place. Hold the dryer at a distance to protect the specimen from strong blasts of air that could dislodge fibres.

Birds

Feathered specimens should never be vacuumed or wet cleaned; however, they can be carefully dusted with a soft squirrel-hair paintbrush or a bulb air puffer brush of the type designed to blow dust from optical equipment and cameras.

The faces of some mounted specimens are made of modelling material that has been retouched to portray the natural colouring of the animal. If the skin shrinks or moves this may crack or break. Small cracks can be carefully filled with a fine surface cellulose filler, such as traditional Polyfilla, and retouched with watercolour paint. The filler and watercolour are easily removable, thus preserving the integrity of the object and permitting corrections or further conservation as necessary.

However, if large areas are missing or broken consult a natural history conservator or qualified taxidermist. And take care when using commercial fillers. Some brands may bond tightly and not be removable. Powder forms may be safer then ready-mixed versions, but all formulations are liable to change as products develop. It is reasonable to suppose that manufacturers will see high adhesion as a sales benefit, and that filler products will develop in that direction.

Reptiles and fish

Reptiles and fish can be vacuumed in the same manner as mammals, and dusted with a soft brush and a bulb puffer. Some early reptile and fish specimens may have been lacquered with shellac, which turns yellow-brown over time. This lacquer should only be removed by an experienced taxidermist or natural history conservator.

Wet cleaning of fish is very risky. Some fish may have had a water-soluble coating applied to their scales to create a more realistic wet look, or could be coloured with water-soluble pigments. Wet cleaning is likely to remove these coatings and pigments, so should not be attempted without qualified advice.

Reptiles can be wet cleaned by rolling a damp cotton wool bud over the skin in the direction of the scales. Take care not to wet the skin or rub it as this will cause damage, especially to small delicate reptiles. Like fish, some reptiles may have had pigment applied to the skin to enhance the appearance. Carefully test a small area before attempting any wet cleaning.

Health and safety

Many older mounted specimens may have been prepared using mercuric soap or arsenic. These treatments protected them from insect attack but persist indefinitely, presenting a hazard to anybody who subsequently touches the specimen.

Other sources of contact hazard, and not just in older specimens, are powerful synthetic insecticides such as DDT and dieldrin. These chemicals were certainly effective against pest attack, and may have figured in the 'best practice' treatments of their day, but they have two harmful attributes. One is their toxicity, and the other is their persistence - qualities that ensure that these and similar insecticides are now banned. The same characteristics that gave rise to their much publicised persistence in food chains keep their toxicity levels high after years or even decades have passed.

The remedy for all staff handling natural history specimens is obvious. Always wear disposable gloves when handling specimens, and always wash your hands thoroughly afterwards. Where a specimen is especially dusty it is advisable to wear a dust mask during initial cleaning.

If you decide to use an insecticidal spray on a specimen (see below), always read and follow the health and safety instructions on the label. Try to use environmentally friendly alternatives, and ask for fact sheets and other information if you are uncertain about characteristics such as toxicity and persistence. Use any chemicals in a well-ventilated space, outside visiting hours, and do not overspray.

Insects and Pests

Mounted specimens are composed of skin, hair and feathers, and are often stuffed with organic materials such as sawdust, so they are susceptible to attack by a wide variety of insect pests. Insects progressively degrade a specimen by boring holes and channels and grazing on fur and feather, and the debris they create can contribute to other problems such as mould growth.

Few specimens are completely shielded from insect attack. Uncased specimens are obviously vulnerable if conditions are favourable, and unless guaranteed airtight even the best cases incorporate tiny gaps - between a door and frame, for example - through which small insects can crawl.

The importance of regular inspections

Inspect specimens regularly, especially during the spring and late summer. Get to know the life cycle of the most common pests, and time your inspections accordingly. Look for live insects or larvae, signs of new damage, and 'frass' - a gritty, grey or black powder composed of droppings and debris. Other signs of infestation are hair or feathers, discarded skins, and dead beetles or moths.

If your specimen is not in a sealed case, check its legs and feet, and any creases and folds. Insects tend to lay eggs in cracks and crevices, and the larvae shun light and seek similar hiding places. A powerful light will help in your inspection. It is important to remember that it is the insect larvae that cause the damage, not the adults.

A selection of common pests

  • Anthrenus verbasci, the carpet beetle, is about 2-3 mm long, round, and bears a pattern of black, yellow, brown and white scales. The small, brown, hairy larvae are known as 'woolly bears'. With experience, the larval cases are easily recognised.

  • Stegobium paniceum, the biscuit beetle, is about 2 mm long, elongated and brown.

  • The adult form of Tinea pellionella, the case-bearing clothes moth, is a small grey/brown moth of about
    4-6 mm in length. The larvae make distinctive tubular cases that look like small white maggots.

Use a genuinely environmentally friendly spray such as 'Constrain' to control insect infestations. Follow all instructions supplied with the product and do not use excessive amounts of the spray. Pet shops sell sprays for household pets or pet bedding, but these should be used with caution, and not just on the strength of label claims - the expression 'environmentally friendly' is used somewhat freely. Unlike dieldrin and DDT, modern non-persistent sprays do not (or should not) remain active on the specimen over long periods, so any treatment will be effective for a limited time only.

Freezing is another option, and for suitable specimens of a manageable size offers a treatment free of the disadvantages of chemical sprays. Wrap and seal the specimen in a polythene bag then place it in a freezer at -18ºC for seven days. At the end of the treatment period remove the specimen from the freezer and leave it, still fully wrapped, to reach room temperature. Remove the wrapping only when the entire specimen has reached room temperature, which may take 24 hours for the core. Domestic chest freezers are normally capable of the required temperature; front-opening models may manage it provided the door is not opened frequently. Commercial freezers operate at about -30ºC.

Sources of information and advice

The newsletter of the Natural Sciences Conservation Group is available from:

Ms M Reilly
Treasurer and Membership Secretary
Hunterian Museum
Glasgow
G12 8QQ
Tel: 0141 339 8855
Fax: 0141 307 8059

Entwistle, R. (ed), Life after Death, Conference Proceedings. Available from:

United Kingdom Institute for Conservation (UKIC)
109 The Chandlery
50 Westminster Bridge Road
London SE1 7QY
Tel: 020 7721 8721
Fax: 020 7721 8722

Ball, S. and P. Winsor, Integrated Pest Management, MGC, London, 1993.

The Guild of Taxidermists
The Royal Museum of Scotland
Chambers Street
Edinburgh
EH1 1JF
Tel: 0131 247 4231

Suppliers of Constrain insecticide spray:
Historyonics
17 Talbot Street
Cardiff
CF1 9BW
Tel: 02920 398 943
Fax: 02920 235 193

The inclusion of a supplier or product within this Fact Sheet does not imply the approval or endorsement by MLA of the product or service. You are therefore urged, in your own interests, to ensure that any product or service is appropriate to your needs.

For more information about private conservation work please contact:

Conservation Register
Tel: 020 7721 8246

Conservation Register (Scotland)
Tel: 0131 668 8668

Copies of this fact sheet can be provided in alternative formats. Please contact Viola Lewis, Information Officer at MLA for further information.

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