The Collection Care and Conservation unit includes staff members with skills outside of traditional conservation, such as taxidermy. Our work is divided into two major areas – preventive and treatment – to control deterioration of the Museum's collections, and to stabilise and/or improve the condition of significant individual objects.
Preventive conservation programs
- environmental monitoring and control
- pest control
- packing and transport of fragile objects
- disaster preparedness planning
- object handling
- improving storage systems
- remedial treatments as required
- preparation of objects for loan to other museums and cultural centres
- exhibitions at the Australian Museum
- larger scale complex treatments
Staff investigate new techniques and materials which will improve the preventive and treatment programs. The unit provides advice and training on preservation of cultural material for Australian Aboriginal communities and museums and cultural centres in South East Asia and the Pacific. Respect for communities' cultural property and ensuring the integrity of natural science specimens are always a key consideration in our decisions.
Infestation by insect pests is one of the most damaging things that can happen to a collection. A commitment to prevention is the best way to go to ensure its long-term survival.
Physical control – This is the application of screens and seals to doors and windows; careful inspection of all new acquisitions as well as the main collection; and the use of sticky traps to monitor the presence of insects.
Cultural control – This is the regular inspection of all items in collections. This includes regular inspection of storage and exhibition spaces along with good housekeeping (keeping all areas clean with no food or drink).
Chemical control – This is the careful application of pesticides where necessary. When chemical control is needed, natural pyrethrum and synthetic pyrethoids are usually chosen due to their safety.
Checking for infestations:
- It is useful to make regular inspections of the exhibition and storage spaces.
- A powerful torch will help enormously in the inspection process to look for eaten areas and holes in objects, dead insects, insect droppings and insect frass (wood powder left by the insect).
- It may be a good idea to seek professional help to fumigate the space so the keeping place can start with a clean slate.
- It is useful to check the collection as well as around the edges of rooms, in cupboards, under shelving, behind furniture and around and equipment that gives off warmth.
- Beetles that breed in flowers, attack skin, hair and wool. This is frustrating, but if the keeping place is decorated with Bottle Brush flowers for example, they can be sprayed with a nursery bought pyrethran before they are brought into decorate the space.
Blunder traps are very useful as they trap a sample of the insects that are active in the vicinity. The traps are simply a layer of adhesive on a card with a cardboard frame surrounding it. They can be purchased in supermarkets and hardware stores. The traps should be placed around the inside perimeter of the walls, under showcases and behind shelving. The traps can be changed every 6 to 12 months. (If the traps are still sticky there is no need to change them).
If insects are found in the blunder traps, they can be identified by yourself, by the entomology departments of state museums or by the CSIRO. If the insects are identified as being a problem, the next step is to find out where the insects are coming from. This may be from outside, through open windows or under doors, behind warm computers, fax/phones, or breeding in an objects such as hair/seed necklaces or feathered headdresses for example.
What to look for on objects
Insects such as cockroaches, moths and silverfish can attack feathers, seeds and human hair string. Obvious evidence can be found by finding eaten sections of the object, live insects, dead insects and insect droppings.
Insects are sometimes found in various unseasoned woods used for carving. With green timber, the insect can be already in the wood as it has infested the growing tree.
Such items that might have been infested in this way are wood carvings, bark paintings (rare) and seeds.
The most common insects to be found are:
- Longhorn beetle that leaves large exit holes up to 9mm oval shaped. They tunnel into the sapwood of a carving.
- Lictus (powder post beetle) leaves many small holes and a talc powder-like frass.
- These insects are only of concern to living trees. They will not infest the rest of the collection as they emerge from the carvings.
- Insects found in seasoned wood (a few years old), are those that have attacked the wood from outside. The most common insects to be found are as follows. Furniture Beetle that leaves a gritty sand-like frass. It will lay its eggs back into the wood and die. It is essential to check the surrounding collection as they will go from one object to another.
- The Bostrichen beetle leaves large holes (5 - 6mm) and the frass is sand-like.
- Termites can attack wooden items such as carved trees that are indirect contact with the ground such as on a concrete slab. By lifting the object off the ground the problem can be solved. It may be useful to get an inspection by a professional pest control officer, as termites can be very damaging to a building.
- In the tropics it may be possible to have a problem with Jewel Beetles. They make large holes in the unseasoned sapwood in a similar way to the Longhorn Beetle.
Treatment of infestations
If an item is found to be infested, it can be put in a sealed plastic bag so other objects are protected.
The Australian Museum for example treats all objects as they arrive into the Museum with low oxygen, freezing or nitrogen gas flushing. It does not use any chemical fumigant.
Freezing for smaller items (or large ones if a commercial freezer is accessible) seems to be an effective and safe way to handle artifacts that have already been infested by borers. The process will kill borer at all life stages including termites, moths, beetles, their eggs and lavae. It is useful to remember that freezing will kill the infestation but will not prevent further attack. Canvas, seeds, hair, wood, bark, feathers, fibre, leather and textiles can all be treated by freezing, but caution needs to be exercised on items which become brittle with freezing, such as shell, resin and glass.
Freezing paintings on canvas is not normally recommended by museums because of the slight potential for the paint to crack. However, if harmful live insects are found, then this is the easiest way to get rid of the problem.
The technique described below has been used at the Australian Museum and other institutions for many years. It provides an efficient and inexpensive alternative to toxic fumigants.
- The object to be treated is bagged in plastic. (Garbage bags will do so long as they do not have any holes in them)
- As much air as possible is taken out of the bag.
- The bag is closed with water proof tape or a heat-sealer (if available).
- The bagged object is then placed in the freezer for 7 days at -20°C.
- The bagged object is removed from the freezer and allowed to thaw in the bag
- The object is taken out of the bag a day after it has come out of the freezer. This is to make sure the object has reached room temperature while it is still in a plastic bag.
Mould can be very damaging to a wide range of objects. Mould grows on organic materials when the relative humidity remains above 65% for a prolonged period. It is disfiguring, can stain and obscure the surface, or even penetrate through the whole structure of an object.
To help prevent mould growth, you should try to keep your valuable objects in rooms with low relative humidity and good airflow. Mould growth is most likely to start in corners and in cupboards where there is little air movement. External wall surfaces in a room are also likely problem areas due to condensation of moisture on the colder surface and also through rising dampness evaporating from the surface of the wall in some buildings. Mould can sometimes be found growing on the back of paintings and textiles hanging on external walls due to the trapped moisture.
Mould growth may be lessened by ensuring good airflow during humid periods with fans and by opening cupboards. Equipment that draw moisture out of the air can also be installed in a room but only work effectively if the room is kept closed. Likewise, the use of silica gel as a desiccant can only work if sufficient is placed the space to cope with the volume of air and any additional air which entering. In reality, this requires a great deal more than a small bowlful of silica in a wardrobe-sized space.
Prevention of mould is preferable but if mould growth appears it can be cleaned off to some degree. Objects displaying fresh mould growth should first be dried off in a well ventilated area. Sunlight can also be used as the UV light in sunlight may kill some of the mould. Avoid the harshest sunlight in the middle of the day as this could dry and split wood on artefacts or accelerate the fading of dyes on fabrics and watercolour paint
There are sprays available in the shops for killing mould. Those that contain ethanol, water and orthophenylphenol can be used on non-painted surfaces.
The dry mould can then be brushed off the surface into a vacuum cleaner nozzle. A very soft brush should be found which cannot mark the surface.
NB: Killing the mould with sprays or UV light will have only a temporary effect if the artefact is put back into the same unsuitable conditions. There are always mould spores drifting in the air that will colonise suitable environments.
Mould is dangerous to your health - always wear a dust mask when dealing with mould growth.
It is important to store textiles properly to avoid damage over time.
Flat in drawers with lifting sheets. If you need to fold them place a small cushion (cotton filled with dacron) or roll of cotton inside the fold to prevent creases developing with time. Hanging on well-padded coathangers (cotton and dacron or acid -free tissue paper. This takes the strain off the seams and prevents creases developing. Large textiles like tapestries or patchwork quilt covers can be rolled onto a large cardboard or plastic roller. Polypropylene is better than PVC and cardboard should not be the coarse brown type which contains acids. Use tissue or cotton between the layers as you roll it. This will prevent bleeding of the dyes from one layer into the next.
Inspect regularly for insect infestation. Silks and wools are particularly vulnerable to several species of moth and beetle. Bag in polythene and freeze for 48 hours any infested material.
For the last 80 years, fishes in the Australian Museum fish collection have been fixed in formaldehyde and then stored in alcohol.
Fixation using formaldehyde is a chemical process during which the proteins in the specimen are cross-linked. Fixation prevents the breakdown of tissues resulting from the release of enzymes after tissue death (autolysis).
Formaldehyde fixation results in hardening of the tissues. This is desirable for the long-term durability of the specimen.
Formaldehyde fixation involves immersing the specimen in 10% formaldehyde for several days up to weeks depending upon the size of the fish. Specimens are then stepped up through a series of alcohol baths of different concentrations. This procedure produces excellent specimens that can be used for a wide range of research and other uses (more information).
Prior to the use of formaldehyde, specimens were usually fixed in alcohol. Over the last 10 years we have resumed fixing specimens in alcohol, in addition to fixing fishes in formaldehyde. Both methods of fixation have their advantages.
Alcohol fixed specimens (and frozen tissues) are increasingly being loaned to researchers who are conducting genetic work. These workers need tissues that have been fixed in alcohol (or frozen), not formaldehyde, because formaldehyde changes the DNA in the sample.
Gloves are an important part of collection care as they protect artefacts and specimens from being damaged when they are handled. Bare skin naturally contains salts, oils, acids and other chemicals introduced through the use of cleansers, soaps and hand creams. These can be easily transferred to the surface of an object causing damage such as:
- Permanent staining and marking to unglazed and porous ceramics
- Permanent etching of polished metal surfaces especially bronze or silver
- Marking and soiling to modern paintings, un-primed canvases, and plastics
- Staining or soiling of stone and marble, and alabaster
- Staining and soiling of some plastics
Gloves also protect collection material from physical damage caused by fingernails, and jewellery. Conversely it is important for hands to be protected from substances that may be on the surface of an object, such as:
- Friable and/or toxic pigments
- Natural poison on spearheads
- Mould on natural history specimens
- Chemicals used for pest control
There are different types of gloves used in materials conservation, the most common is white cotton gloves. However, cotton gloves are not always appropriate as fibres can snag on rough surfaces; they do not provide good grip on smooth surfaces; and friable pigments can easily be abraded. In these instances nitrile or latex gloves are often used.
The fixation technique is designed to preserve the cellular structure of the specimen so when observed under the SEM the dead specimen will (should) resemble that of a live specimen. This process offers the scientist a close up look of what the cells, ie skin, head, organs etc look like when alive.
Various chemicals processes are used to fix the specimen. These chemicals are very dangerous to human health and care must be taken when dealing with them.
To extract the part we can use various ways. One way is to simply cut and pull the wanted part carefully away from the body (a manual dissection). Another way is to use chemicals which eat away the soft body material leaving only the wanted hard bodied sections (the exoskeleton, the snails teeth).