How do I prevent insects damaging my artworks?
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 longterm 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.
2. 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.
3. 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.
Colin Macgregor , Manager, Materials Conservation