The most frequently asked questions of the McMichael come from individuals who want to know more about caring for their art at home. Following are answers to your most common questions.
In a museum setting, the environment is controlled to levels of temperature and relative humidity that are optimum for the long-term preservation of the works of art, while at the same time allowing for human comfort. Ideally, temperatures are kept between 19 to 21°C and relative humidity between 40% and 55% with a fluctuation not greater than 5% in a day. In a private home where it may be impossible to duplicate museum conditions, environmental stability can be more closely approached by careful selection of the locations used for the display and storage of works of art.
When selecting a location to display your works of art, a number of factors should be kept in mind:
- Interior rooms will have more stable environments than rooms with outside walls.
- Locations that are open to the outside (i.e. rooms where windows are open) will suffer from great fluctuations in temperature and relative humidity. Exterior walls will be, in certain seasons, colder and damper than interior walls in the same room.
- Areas above or immediately adjacent to heat sources like hot air vents, radiators and fireplaces, will be hot and dry and suffer from wide fluctuations in temperature and humidity.
- Kitchens and bathrooms are unsuitably warm and damp for hanging works of art.
- Attics are often poorly insulated and follow fluctuations of outside temperatures.
- Basements are often cool and unacceptably damp.
- Ventilation gaps left between each object and the wall will prevent excessive cooling and dampness.
- Automatic portable humidifiers and dehumidifiers can contribute greatly to the stabilization of the relative humidity in a room when appropriately sized for the space.
Minimizing Light Damage to Art
Light is necessary to view art, but at the same time can damage many of the materials found in paintings and works of art on paper. Light can fade pigments, and cause paper and textiles to discolour or become brittle.
Light levels in museums are controlled to minimize the deterioration that light causes. In our homes, however, light levels are generally much higher than in museums. Light levels are measured in lux. Recommended levels in museums are 50 lux for works of art on paper and 150 lux for paintings. A work of art hanging in your home in direct sunlight could typically be subject to 20,000 lux or more – hundreds of times the recommended level.
In addition to keeping the light levels low in a museum, we also eliminate the ultraviolet (UV) portion from any light source. We have all become aware in recent years of the potential damage to our skin from high levels of UV in sunlight. The UV portion of the spectrum is also the most damaging to works of art. Fortunately, it is not part of the visible light we need for viewing, and is easily removed.
Tips for Home
When hanging works of art in your home, there are many things that you can do to minimize the damage caused by light.
- Fit windows with blinds or curtains that are kept closed when the room is not in use.
- Locate your pictures so that they will not be exposed to direct light. For instance, the wall opposite a window will get direct light, while the wall beside a window will not.
- Do not use "picture lights" designed to attach to frames. In addition to over-lighting, these cause local heating that is also damaging to works of art.
- Use incandescent light, which has no UV component, to light works of art. Select low wattage bulbs and use a dimmer switch to set the lighting at the minimum level which allows you viewing comfort.
- If fluorescent lights are used, UV filtering should be incorporated either as sleeves or lenses over the source of the light, or by using UV absorbing Plexiglas to glaze the works.
- Works of art on paper with coloured media (i.e. watercolour) and poor quality paper such as newsprint are particularly vulnerable and quickly damaged and should not be displayed on a permanent basis.
Matting and Framing Works of Art on Paper
Works of art on paper are commonly matted and framed as a means of both display and protection. Paper is a fragile material and vulnerable to damage from handling and environmental agents such as light, temperature, humidity, dust, air pollution and exposure to poor quality matting and framing materials. There are many considerations in proper matting and framing of which the collector of paper objects should be aware.
Presentation is the usual priority of commercial framers and it is unfortunate that more often than not matting and framing methods used by them do more harm than good. However, some framers will use acceptable methods when properly instructed by the client.
A mat in its simplest form consists of two boards; the backing board and the window board. The board used must be of good quality as the decomposition products in poor quality boards will eventually migrate to the artwork causing discolouration and embrittlement. There are many good quality mat boards on the market but the consumer must be wary of certain jargon that is used. Unfortunately terms such as "acid-free" or "museum quality" do not ensure quality. The board must be made from a good quality fibre such as cotton or if it is wood fibre only alpha cellulose pulp is acceptable. The board can be slightly alkaline or have a neutral pH. The latter is recommended for matting photographic materials. A reliable supplier should be able to supply the technical specifications for the board.
Mat board is generally available in two, four, and eight ply weights. As the work of art is attached to the backing board, the board needs to be of sufficient thickness to adequately support it. Four-ply is the minimum that should be used to provide adequate support to an average size work of art on paper.
Museums generally choose white or cream coloured boards. Coloured boards of acceptable quality are available but the board chosen should be lightfast and not bleed in the case of accidental water damage.
The purpose of the window board is to provide a space between the artwork and the glazing material. The window opening is usually cut with a 45° bevel to reduce shadows being cast. The window can be cut to either cover the margins of the artwork (overmat) or to reveal all the edges (float mat). In the case of an overmat the edges of the mat must cover the edges of the work by at least 0.5 cm to ensure that the mat will adequately hold down the work. For a float mat a similar distance of at least 0.5 cm should be left between the beveled edge of the window and the outer edge of the artwork. The borders of the window mat must be wide enough to adequately accommodate the edges of the work that it is supposed to cover. Generally speaking the borders should be at least 5 cm. However if the edges of the artwork that are under the window board are wider than this, the borders of the window board will need to be wider as it is unacceptable to trim or fold the edges of a work of art.
It is sometimes necessary to incorporate an additional spacer in the frame rebate to prevent the matted work from coming into contact with the glazing material. Spacers are used for works of art that do not lay flat, those that have thick media layers and for oversize works. They are also used when a window board is not aesthetically pleasing such as with some contemporary works.
The backing board and window board should be hinged together on the top or left edge (whichever is the longest) with gummed linen tape. Gummed linen tape is not, however, a suitable material for attaching the work of art to the backing board.
Attaching the Work of Art
The purpose of a hinge is to provide a means of securely attaching the artwork to the backing board. The best way of doing this is with paper hinges adhered with starch paste. A work of art should never be adhered directly to a window or backing board. The hinge should be made from a material that will not damage the artwork through transfer of acidity and be of a suitable weight to support the work but not so heavy that it causes embossing.
Good quality Japanese paper is an ideal material to use for hinges as it is strong and comes in a variety of weights. The paper chosen for the hinge should be of a similar weight and thickness to the artwork, never heavier. It should be noted that not all Japanese paper is of a suitable quality. As with mat board the fibre content of the paper should be checked and a reliable supplier can provide this information.
A two-piece hinge commonly known as a T-hinge is normally used as it is strong and the mechanics of it allow for some expansion and contraction of the artwork in response to changes in relative humidity. The edges of the Japanese paper hinge should be feathered to avoid any hard edges that may cause ridges in the artwork. The hinges are applied on the top corners of the reverse side of the work. Depending on the size and weight of the artwork, additional hinges are also placed at equal intervals on the top edge. The size of the hinges is also dependent on the needs of the artwork but they are generally 1.5 to 3 cm wide. The portion of the hinge that is actually adhered to the artwork is minimal (approximately 0.5 cm). The hinge when attached to the artwork must be allowed sufficient drying time under restraint to avoid distortion of the artwork.
The adhesive used to attach the hinge should be starch paste. Unfortunately, commercial preparations of a suitable paste are not available and paste must be prepared freshly for the purpose. It is however an easy process and can be done in a double boiler or more quickly in a microwave oven.
Most commercial framers use tape (either gummed linen or a variety of pressure sensitive) to hinge the work. Even when sold as "acid-free" or "archival quality", these tapes are not suitable as they can cause irreversible damage to the paper.
The second component of the hinge is a strip of Japanese paper that secures the first hinge to the backing board. This part of the hinge is cut (in this instance it is not necessary to feather the edges as this part of the hinge does not come into direct contact with the artwork) approximately 3 cm longer than the width of the first hinge and 1 cm wider than the height that the hinge extends about the top of the work. It is coated with paste, centred over the first hinge and stuck onto the backing board just above the edge of the work of art. This type of hinge is used for an overmat style of window mat but can be adapted as a V-hinge to use in a float mat situation. Again this second hinge needs to dry under restraint in the same way as the first hinge.
Frames can be made of wood, plastic, or metal and come in a great variety of styles and finishes. The frame needs to be adequately strong and well secured at the corners. In addition the rebate needs to be deep enough to accommodate the artwork in its mat spacer (if any), glazing and frame backing board with space for securely fastening the frame backing board to the frame.
A frame backing board should be placed behind the backing board of the mat to provide additional support for the framed object. This backing board should be of a good quality rigid material such as foam-core, Coroplast or acid free corrugated board. It should be secured to the frame with non-corrosive nails, framer’s points, a backing insert, or spring clips in the case of metal frames. A dust seal comprised of a good quality, acid free paper can be attached to the back of the frame with double-sided pressure sensitive adhesive tape or a water based adhesive. It is also a good idea to provide a seal between the glazing and the frame and this can be done by the application of a tape such as Filmoplast P91 around the edges of the glazing and mat package.
The glazing material can be glass (either plain picture glass or a non-reflective variety) or acrylic sheeting (e.g., Plexiglas). Acrylic sheeting that incorporates an ultraviolet filter can be used if ultraviolet light levels cannot be controlled in other ways but it has a yellow cast and does not reduce the amount of visible light reaching the work of art. If there is friable media (e.g. soft pencil, charcoal, pastel) present on the artwork then glass should be used as the static charge present on acrylic sheet could attract loose particles of media. Aside from the obvious disadvantage of glass being breakable, it is heavy and can be problematic when framing a large work. Acrylic sheeting is generally more expensive and has the disadvantage of easily scratching.
Any labels that are found on the back of frames or backing boards should be saved and kept in files or secured to new frames. A reliable framer should make a note of the materials used. Finding a reliable framer can be difficult and it is advisable to consult with a professional conservator who can either make a recommendation or prepare the artwork in a mat so that it can be safely taken to a framer.
Properly framing a painting is one of the most valuable things that you can do to protect it and ensure its long life. Framing is a system made up of several parts: the frame (which may not be appropriate for all works), the backing board, rebate padding and glazing where needed. For each, there are principles to keep in mind.
The frame: To be adequately protective, a frame should be strong and rigid. It should support the painting rather than relying on the painting for support. The edges of the frame should extend some distance - at least a centimetre and preferably more - above the surface of the work, so that if it is bumped contact is made with the frame rather than the painting.
The backing board: All paintings, but especially paintings on canvas, benefit greatly from a well sealed backing board which protects the back of the work from damage due to physical contact, creates a beneficial ‘micro-climate’ for the vulnerable exposed support and provides an air cushion which dampens vibration when the work is moved. Any strong rigid material - cardboard, foam core, Masonite - can be used for a backing board, but fluted polyethylene Coroplast is ideal. For a painting on canvas, the backing board should be secured to the reverse of the painting’s stretcher with screws.
Rebate padding: The rebate of the frame should be padded to protect the edges of the painting from abrasion. Felt or velvet ribbon, adhered with an ordinary white glue (like LePage’s Bond Fast) works well, but it is extremely important to allow a twelve hour drying period after applying the glue before the painting is framed.
Glazing: Where a painting surface is particularly porous, or the atmosphere especially dirty, glazing is required. Either glass or Plexiglas can be used. The most important thing to remember when glazing a painting is to keep the glazing well away from the surface of the work. Installing glazing between a frame and a liner is one technique for accomplishing this.