‘Conservation framing’ is a term used to describe the use of materials and techniques which provide protection to framed works of art on paper. There are different levels according to the quality and specification of the materials used.
A mount and frame will always be selected by Riverbourne Framing to protect as well as enhance a picture. Unfortunately, some mounting and framing techniques not only fail to protect, but are potentially damaging to works of art.
Paper is sensitive to its surroundings: it can be adversely affected by damp, changes in temperature and humidity, restriction of movement and exposure to light. Paper will also react to the materials with which it is in contact such as acidic support boards and self-adhesive tapes. Evidence of damage caused by adverse conditions can be seen in pictures with mount burns, foxing (small brown spots), fading of pigments or darkening and increasing brittleness of the paper.
If the picture is damaged, foxed, stained or stuck down onto an acidic card backing, Riverbourne Framing can advise on preservation and conservation options. In some cases, preservation may mean leaving well alone and simply ensuring that the picture is well protected through conservation framing; in other cases conservation treatment may be essential to protect the picture long-term.
The framing of a work of art may involve making a choice between re-using an existing frame and selecting a new one. It is vital that the frame rebate should be deep enough to hold the glass, thick window mount or fillets, object, thick under mount and back board. The frame must be both strong enough and deep enough to support the whole package. An old frame will sometimes need to be modified by Riverbourne Framing to meet these criteria.
The conservation mount comprises a window mount and under mount (sometimes also referred to as a back mount). To provide adequate physical and environmental protection both boards used are at least 1.3 millimetres thick.
Conservation mount board
Because the picture is in direct contact with the mount, the choice of mount board is crucial to protecting framed works of art on paper. As a guide, there are three main categories of mount board and framing:-
1 Museum level
For framing valued original works on paper cotton museum mount board is selected, this is usually solid core, made from 100% cotton fibre – a traditional paper making material, proven stable over hundreds of years. It can be un-buffered (neutral pH) or buffered with an alkali deposit which prolongs the stability of the board and provides some extra protection.
2 Conservation Level
Conservation mount board. This refers to board made from chemically purified wood pulp and then alkaline buffered. Like Cotton Museum board, the core and facings must meet certain criteria such as light fastness, pH ranges and quality of lamination adhesives.
Mounting photographs – photographs are a special case because some types may be affected by alkalinity: they should not therefore come into contact with an alkaline buffered board. A pure, unbuffered cotton museum board will be used. MicroChamberTM board – MicroChamberTM technology is the trade name given to products which contain molecular sieves (zeolites) which ‘trap’ pollutants commonly found in the environment and may be generated internally within the frame package. This proactive protection will ‘trap’ by-products harmful to paper such as acetic acid, aldehydes, and sulphur dioxide. Cotton Museum board and Conservation board are available with these fillers for this type of work.
3 Standard level
Standard mount board, this is made from un-purified wood pulp. Un-purified wood pulp will gradually break down and release acidity, thereby damaging the picture. Although many wood pulp boards are now buffered with an alkali and described as ‘acid-free’, this is misleading and is no longer a viable marketing term for any mount board and is not recommended for conservation framing.
It is best to avoid sticking artwork down to a backing card as restriction of movement can be detrimental. Hinges will allow the picture to hang safely; they are applied to the top edge and adhered to the under mount.
Adhesives used are easy to remove at a future date, and neither stain nor darken with age. Riverbourne Framing like to use specialist conservation paper hinges as they are thin pliable and strong.
Pressure sensitive tapes, such as SellotapeTM and masking tape have no place in conservation framing. They cause permanent damage to the picture by staining and become difficult or even impossible to remove.
Glazing and conservation glazing
Works on paper are mounted clearly away from the glass to allow for air circulation and movement. Pastels and chalk drawings are held at least 5-6mm from the glass, using either double or triple mounts. If the picture is to be ‘close framed’ (without a window mount) it will be held away from the glass with a small slip, card or fillets (4-6mm deep) tucked under the rebate. There is now a wide range of glazing materials with different optical properties that can be used in framing. Ashley will discuss the various glass options available for your particular framing project and advise on the best option for your artwork.
Reducing light exposure
Museum level framing requires the use of UV filtering glass and is also strongly considered for conservation level too. Light exposure has a pronounced effect on paper condition and pigments.
The harmful effects of light can be reduced by using ultra violet filtering glass or UVA Acrylics.
PerspexTM and PlexiglassTM can be used because they are lighter and unlikely to break on impact. However, these materials do scratch more easily and because of static, they are never used by Riverbourne Framing to glaze pastels, chalks or any other friable materials.
The mounted picture/glass sandwich is sealed around the edges with gummed paper to prevent thunder flies or pollution from penetrating the frame.