ISSN 1753-9854 AUTUMN 2004
Paintings on Canvas: Lining and Alternatives
STEPHEN HACKNEY
The structural treatment of deteriorated oil paintings on canvas is a major concern of paintings conservators. In the past, the attachment of a second canvas to reinforce the weakened original was universal practice. This was called re-lining and later became known as lining. But in recent years the value of lining has been questioned and its disadvantages documented. A major change of opinion has occurred, reinforced by modern attitudes to conservation which place greater emphasis on preserving the original state of the canvas support and applied paint film. These attitudes in part derive from a more academic education that conservators now receive. This has largely replaced apprenticeship training, which tended to reinforce the strengths of existing practice. Now, a less interventionist approach is taken. But this approach is very dependant on the accuracy and relevance of engineering models derived from recent scientific research. The application of this knowledge to conservation practice creates an ongoing dialogue about the aims, aesthetics and ethics of conservation.
The 1974 Comparative Lining Conference
In 2004 the UKIC held a meeting on the subject of ‘Alternatives to Linings’.1 The meeting coincided with the belated publication of the often referred to papers from the Greenwich Comparative Lining Conference of 1974.2 These two events were an opportunity to take stock of changes during the last thirty years to conservation practice for the structural conservation of canvas paintings. This paper presents an overview of the subject and is illustrated by some examples of solutions to structural problems that have been used regularly.
The Greenwich Conference was a very significant
event since it was the first opportunity to discuss this subject. It brought
together a group of specialists from around the world with very different
views of what was required from a lining.3
There was little meeting of minds on solutions, each
described their own practice, but the full range of problems was at least
identified.4 In retrospect
its main value was to identify the inadequacy of our understanding.
After the conference, since there had been no agreement
on what constituted a good lining, W. Percival Prescott, co-ordinator
of the conference, called for a moratorium on lining to give conservators
time to take stock of the situation.5
This was not what I wanted to hear and it took me some time to see its
value. We had identified a hugely important issue in conservation that
needed solving. My initial response was a desire to find out more and
to experiment with all the options presented.6
But in museums, so the argument goes, we are able
to defer lining because we know that paintings will be kept in acceptable
conditions and remain available for re-examination, which allows us to
reconsider our treatment if it continues to cause problems. This is not
entirely true but in a museum the argument for carrying out a lining has
a higher threshold.
Lining was seen as a solution but the criteria
for lining had never been properly addressed. At Greenwich there was much
confusion between the need to provide a sound support and the need to
re-attach the paint film to the original canvas. What is a sound support?
One that copes with handling and transport, tensions from humidity and
temperature changes, is chemically stable and visually acceptable. A marouflage
is a sound support, but that is an extreme solution. What about more subtle
solutions? It was clear that we needed to know much more about the painting
and the conditions to which we intend to expose it.
No-one had addressed the most fundamental questions.
What is happening within the structure of a canvas painting? What forces
exist within the layers of a painting on canvas? What is their magnitude?
Where do they act? What are their consequences? We knew that when a wood
panel is constrained it causes huge forces that can crack it from end
to end. We knew that when rabbit-skin glue dries it can pull off a layer
of glass from inside of a beaker. We knew that pre-stretching can cause
a canvas to split. We knew that in dry conditions paintings become very
brittle and can cause paint to flake. We knew that in humid conditions
canvases can contract, sometimes dramatically losing areas of paint at
the edges - the notorious shrinkers. We knew that with heat and pressure
we can distort seemingly solid paint, mould it to our advantage or fail
to control the application to everyone’s disadvantage.
Whether to line
By examining many examples of glue lined paintings and their conservation records, it was clear that the results of glue lining, particularly in the United Kingdom, had been disastrous (fig.1).7 Impasto was squashed, the canvas texture re-inforced in the paint and the precious evidence of artists’ brushstrokes were forever lost (fig.2). By contrast, the set-backs from modern lining practice are relatively tame. But, of course, we are all personally responsible for the effects of the linings that we undertake.
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Fig.1 Thomas Gainsborough An Old Horse c.1755 (raking light photograph) oil on canvas, Tate. This is an example of a painting that has suffered damage during a glue lining. The canvas texture is reinforced into the surface of the paint and the brush strokes have lost their crispness. © Tate |
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Fig.2 W. R. Sickert, Tipperary, 1914, oil on canvas (detail), Tate. © Estate of Walter R. Sickert On an unlined painting we may appreciate the spontaneity of an artist’s brushstrokes, the nature of the paint and the qualities of stretched canvas. |
Responsibility is the key issue. In the past, the
lining process was carried out by liners (or re-liners), who were often
employed by restorers, who in turn were responsible to the museum curator
or the painting owner. Was the continued insensitivity to lining damage
caused by this arm’s length responsibility? Or was it simply that damage
was thought to be acceptable as an inevitable side-effect of the need
to save the canvas from falling apart? As I saw more old glue linings
it became clear that nineteenth-century liners such as Morrill continued
to cause the same kind of damage over and over again and that this damage
was accepted by museums, which were prepared to send more paintings to
be lined.8
Interestingly, our recent studies of some nineteenth-century
artists’ techniques have also shown that artists such as William Holman
Hunt, Ford Madox Brown, Sir John Everett Millais and James McNeill Whistler
were getting their canvases lined very early or even during the painting
process. They had no concerns about flattening and weave re-enforcement
and we suspect that in some cases they were happy for their canvases to
take on the characteristics of the lined old masters that they had seen
in museums.
In the past our attitudes to physical and structural
threats to a painting have owed more to the excesses and limitations of
our own imaginations. We may imagine that our treatment will last indefinitely
and cope with a range of unpredictable problems. In this case we are likely
to go too far in our intervention. Alternatively, we may imagine that
we must not contaminate our painting with unnecessary material and in
that way fail to prevent deterioration. The key is to have an accurate
model of the future use of the painting and the consequences of an intervention.
Understanding the problem
Since Greenwich we have made much progress in understanding how a canvas painting is constructed and how it responds to its environment and to our actions. Paul Ackroyd has produced an excellent review of the changes in lining practice.9 In particular, careful measurements of the moisture response of painting materials have been carried out by Mecklenburg, Hedley and Michalski. 10
Conservators began to understand that not only
the canvas and sizing but also the oil paint could respond to moisture
very significantly, if slowly, and that the moisture content influenced
the mechanical properties of the paint, making it more susceptible to
the effects of heat and pressure. Moisture treatments were explored. We
could soften some paints but not usually the lead whites. Glue paste linings
and other linings involving heat and moisture exploit this moisture response
whereas linings using wax and synthetic materials had been invented more
recently to avoid it. But glue linings are more effective at actually
flattening raised cracks, not simply holding them tightly in plane. Oil
paint moisture response also explains why so much damage has been done
by glue liners in the past. With enough heat and pressure we could mould
the paint into all sorts of interesting shapes.
Mecklenburg revolutionised our view of the canvas
as support by showing that the glue layer in a new painting carried much
of the load (fig.3).11
The ground and paint layers also carried significant parts of the load,
and the relationships between the layers changed with the changing humidity
environment. As the painting aged and cracked the forces became disrupted
in the painting plane and created the familiar raised cracks and cupped
paint. We could now begin to appreciate why glue paste lining was effective
at holding down raised cracks, whereas other methods were not. The persistence
of the nineteenth-century glue liners at least seemed rational. Could
we learn from their success in flattening cupping and still avoid the
unwanted consequences inherent in their approach?
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Fig.3 The diagram illustrates how all paintings on stretched canvas deteriorate, first through embrittlement and cracking, then through long term relaxation under tension. Much of the tension is carried in the paint and ground, not in the canvas, but where the paint cracks, all the tension is taken by the canvas. Re-alignment of forces causes the islands of paint to cup and separate from the canvas. © Tate |
Thanks to Hedley, shrinkers are no longer a mystery.
Conservators understand the behaviour and effect of a glue layer sitting
as a separate layer on top of the canvas because it was applied cold by
spatula in a thick gelatinous solution by a colourman such as Roberson.
Above 75-80% RH a linen canvas tends to shrink and animal glue loses its
strength. Tightly woven Ulster linens were not as solid and dependable
as we had previously thought. We looked with new respect at the flimsy
open weave Belgian canvases used by many French painters of the twentieth
century.
More recently work by Young and colleagues has
continued to develop our understanding, filling in more detail about internal
and external forces, generating computer models of how a painting and
canvas behaves, and beginning to measure the effects of specific conservation
treatments.12 Should
we be lining onto stiffer fabrics that match the glue for load carrying?
We are still using the same specification of polyester sailcloth that
Hedley found at the Earl’s Court Boat Show in 1981.13
The realisation that a lining canvas is only one
of several important components that hold together a canvas painting has
changed our frame of reference. Separating the consolidation process from
the lining process was a crucial change in thinking.14
If each process has to be justified separately and
a lining canvas is not a unique structural component, the arguments in
favour of carrying out a lining are rare. That has been our experience.
It has been possible to investigate the effects of moisture treatments,
adhesives and preventive treatments in isolation from lining. Indeed,
we have been able to show that we could create nearly all the disadvantages
of lining: weave emphasis, excessive flattening, the marouflage-look,
squashed impasto and moating without attaching a second canvas.
Strip-lining
Given that in the past we understood very little about the complexities of stretched canvas paintings and even now we do not understand everything, the practice adopted by most conservators has been to intervene as little as possible. But when a canvas is around a hundred years old and beginning to show the familiar signs of deterioration, we need to intervene.
Often the tacking edges are more damaged than the
bulk of the canvas because of the effect of the rusted tacks and resinous
wood. We rarely remove a canvas from its stretcher unless it is absolutely
necessary. When we do, we risk damaging the tacking edges, which may not
be strong enough to allow re-stretching. It is then that we resort to
strip-lining, the application of a strip of canvas to reinforce the original
edges (fig.4).15
Strip-lining is often done with polyester canvas
and BEVA adhesive (ethylene vinyl acetate copolymer). This has proved
to be effective over many years. The polyester is thin, stable, and load-bearing
and BEVA is flexible and provides good adhesion. It is heat sealed at
65 degrees centigrade. There is always the question of how far to extend
the strip lining into the picture plane. It must be far enough to carry
the load across the weak edges. Deformation in plane at the strip-lining
edge is much less of a problem with thin polyester and flexible ethylene
vinyl acetate.
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Fig.4 A 150 year old primed canvas which has never been painted displays all the basic deterioration characteristics of a finished painting on a stretched canvas. © Tate |
Strip-lining has largely replaced lining since
it begins to address many of the problems that would once have put the
painting in the category to be lined.
Tears
Tears are often cited as the reason for lining and indeed major tears equivalent to half a painting dimension or more need extra support. But most small or medium tears can frequently be repaired in situ and need not involve lining. The canvas is not normally removed from its stretcher. The torn area is treated with moisture using a brush or swab to shrink the extended yarns back into plane so that they meet again. Depending on the tear this is usually possible to achieve but if serious distortion has occurred it may be necessary to trim some canvas yarns. The areas most resilient to treatment are distortions at each end of the tear where maximum stress concentration has occurred. Placing the canvas locally under pressure using weights, heated spatula and moist blotting paper can usually achieve a reasonable result. Then the canvas can be repaired either by using adhesive or by sewing. Some recent papers have described this process in detail and made useful observations on best practice.16 The essential points are that the tear repair is restricted to the plane and level of the canvas and the immediate area of the tear, and that it provides a rigid structural joint, with the yarns aligned.17 Next, the lost paint is filled and retouched. Often very little paint has been lost and the most extensive part of the retouching intervention is in disguising the more extensive cracking that has occurred around the tear.
Flaking paint
Lining a canvas was once thought to be a valid treatment to consolidate flaking paint. Most paint loss or flaking is caused by poor adhesion between the ground and canvas. Occasionally, due to bad artist’s technique, flaking can occur between paint films. As with other aspects of poor technique this is the most difficult type to deal with, but fortunately relatively rare.
However, the usual problem is the need to re-attach
an original lean white-lead oil ground to a sized canvas. Because the
dimensions and mass of each lifting and potentially flaking piece of paint/ground
is small, Newton’s law tells us that the forces needed to re-attach them
are very small. Indeed, I have seen small raised edges of paint that have
escaped the conservator’s attention remain very stable for years despite
having been exposed to constant handling and display. The demands on the
adhesive are very small, and as we know even wax/resin is enough to hold
an isolated area of paint. It is not surprising then that a multitude
of adhesives has been suggested for consolidation and lining and not surprising
that there is no consensus on the best one.
Perhaps the best adhesive is the most stable one.
In conservation treatments we argue for reversibility but a truly reversible
adhesive or consolidant is by definition not possible.
Our model of a canvas painting tells us that the
canvas tension may well be carried principally in the size and ground,
depending on the humidity, except at discontinuities (cracks) where the
load is entirely carried by the canvas. This is a mechanism that leads
to cupping and flaking of paint/ground and recent work at the Canadian
Conservation Institute suggests that drying of the paint layers may also
contribute to cupping. To counteract cupping, an adhesive with an elastic
modulus at least as high as that of a lean ground would be needed. Such
a structural adhesive would not be removable. We need to decide whether
we wish simply to re-attach the canvas or be much more ambitious and reverse
some of the effects of cracking. The latter approach still needs much
more research and is I think the outstanding issue yet to be addressed
- so we must be content with re-attachment.
If we accept this limited objective I think we
should not worry too much about the nature of the adhesive we choose -
after all it has to form a bond to dried oil, pigment, canvas and rabbit-skin
glue, very different materials. This diversity of surface energy is part
of the reason the original paint failed. The consolidating adhesive needs
to have broad properties. That is why various commentators have justified
vastly different adhesives from fish glue through synthetic emulsions
to waxes.
Prevention
Much of a museum collection of contemporary art should be in good condition but we can be confident that it will deteriorate in a similar way to existing works in the historic collection. In many cases artists are still using stretched canvas to paint on and oil priming has only very recently been replaced by acrylic. There are differences in degree but the structures remain similar. However we can predict that when certain difficult works eventually need to be treated future conservators will have serious or insurmountable problems. We should therefore take action now to prevent or retard deterioration.
Most museums put much emphasis on preventive measures,
reducing risks in handling, transport, display and storage. This has been
the mainstay of the approach at Tate. By introducing procedures for the
physical protection of works of art and restricting direct access to works
of art we can avoid much accidental damage. By improving gallery environmental
conditions and air quality we can reduce physical and chemical changes.
Framing policy has proved extremely effective in
the past 30 years.18
The application of backboards, the strengthening of frames to ensure rigidity
and the application of low reflecting glass whenever possible provides
effective mechanical protection and ensures a microclimate around each
work, which is far more stable than the best air-conditioning system.
The extensive use of carrying/transit frames, wrapped in polythene, for
handling, storage and lorry transport is also a mainstay. Such procedures
are essential, particularly when our collection is used so heavily.
We also prioritise the examination and treatment
of newly acquired works of art, putting them into a condition that pre-empts
some of the deterioration effects that we predict. By surveying the collection
we have identified those works already in the collection that need treatment.
In the past many of these would have been prime candidates for lining
but now we look for alternatives.
Double canvases (loose-lining)
In the nineteenth century several London colourmen sold double canvases, for example W. Brown of Holborn and later, Robersons and Winsor and Newton. Double canvases were regarded as a superior product and were bought by major artists. Many later paintings by J.M.W. Turner were painted on Brown’s double canvases and other established artists such as W.P. Frith, Sir Edwin Landseer, J.E.Millais and W.Holman Hunt also used double canvases.
These double canvases normally consist of a tightly
woven heavy Ulster linen canvas, sized with rabbit-skin glue and primed
with a lean oil ground. The ground is usually pigmented a dull white using
a mixture of lead white and chalk applied by brush in at least two layers.
It is applied evenly and smoothly, as would be expected from a commercial
product. Large pieces of stretched canvas were pre-primed in this way
for both single and double canvas systems.
When the ground has dried, the first canvas is
stretched on a substantial expandable wooden stretcher with the ground
facing the stretcher. Zinc coated iron tacks are normally used. This became
the auxiliary canvas. The second canvas is stretched on the same stretcher,
this time in the conventional way with the ground to the front, again
using tacks. This became the primary canvas for painting on. The intention
was to create a sandwich structure of ground, sized canvas, sized canvas,
and ground. There is no adhesive between the two canvases, which are simply
held together by the stretching process.
A variation on this method was the use of an un-primed
canvas behind the main canvas rather than a primed one. This was cheaper
and no doubt not considered as good.
Examination of the primed double canvases in the
late twentieth century when they were about 150 years old revealed that
the auxiliary canvas grounds had cracked with an almost identical pattern
to the primary painted canvas ground (fig.4). They had cracked extensively
to form a complete network of largely random cracks, which had then opened
and allowed the paint to cup. The moisture response of the tightly woven
linen and the thickness of the ground were the chief contributions to
this.
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Fig.5 A conservator attaches a strip-lining to the edges of a canvas. © Tate |
When these supports were dismantled, removal of
the primary canvas revealed the reverse which was free of dust and appeared
to be relatively well preserved. Similarly, the auxiliary canvas was well
preserved. So this was an effective system of preserving the canvas from
the effects of pollution, both particulate and acid gas, which was principally
sulphur dioxide in the period in question.
However this double canvas system (sometimes called
an original loose-lining) did not prevent cracking and cupping of the
ground and paint, nor did it prevent corner draws and loss of tension.
Many of these paintings were relined in the 1960s, usually in an attempt
to flatten disturbing cupping and undulations. Indeed, the auxiliary canvases
were very useful objects on which to practise the flattening of cupping.
The valuable experience of one hundred and fifty
years of aging revealed by these canvases encouraged conservators at Tate
to use modern loose-linings on more recently painted works, as a preventive
measure, and also for older paintings that we did not wish to line. The
barrier effect of the original double canvases against dirt and pollution
was clear but their failure to prevent the effects of canvas relaxation
was also evident. Rather than use linen canvas for modern loose-linings
we chose to use polyester sailcloth. This material is a fine, even polyester
yarn which has been tightly woven, followed by heat treatment to shrink
the canvas and lock the weave in place. When used as a sail it is designed
to be impervious to wind and therefore it can significantly reduce the
transport of air to the canvas reverse, keeping out all particulate and
most gaseous pollution. The material is not expected to relax or creep
to the same extent as canvas and acts to keep the stretcher in plane.
I have a polyester canvas that I stretched twenty five years ago which
is still very tight. It ought to provide an excellent support.
When a painted canvas is stretched on top of a
polyester loose-lining its weight is supported by the polyester and it
need not be stretched so tightly. It will look and feel tight even though
only a small force has been exerted. This is a very important effect,
which prevents, or at least reduces, the long-term relaxation that would
otherwise occur with a tightly stretched linen canvas, even though this
may not manifest itself for fifty years.
One drawback with a polyester loose-lining is that
the reverse of the canvas becomes invisible and the polyester may even
be taken for the original. If further work needs to be done to a painting
at a later date the loose-lining may need to be removed. An advantage
is that the original stretcher can be retained and preserved by this system
and the total weight is only increased a very small amount.
A rigid support
When the stretcher is inadequate, as with many large modern works, and has to be replaced, the museum conservator may devise an entirely new support system that offers rigidity and protection from the rear. In a museum the extra weight is not such a problem and can even be an advantage. But replacing the support with a more rigid structure is a major aesthetic intervention, changing the nature of the stretched canvas. Not everyone agrees with such a change, although I would argue that it is valid provided it is not discernable from the front when the painting is on display.
A rigid support can be constructed from an aluminium
honeycomb panel of the type used in aircraft manufacture. These are typically
25mm or 50mm thick, very light and rigid. By gouging out a small piece
of the honeycomb at the edges a shaped piece of softwood can be inserted
all the way round. This provides an edge that can take tacks or staples.
It is then possible to stretch a canvas over the panel and attach it as
on a stretcher. Like a loose-lining the panel provides support and allows
much less tension to be used. A piece of paper is usually attached to
the front of the panel to isolate it from the back of the canvas and also
to provide friction. Being completely impermeable to moisture, the panel
ensures stable conditions exist between it and the canvas. Being rigid,
it provides a stable tension and protection from impacts from the reverse.
Physically, it is the ideal support and readily reversible.
There are limits to the dimensions of individual
panels but they can be joined indefinitely to make larger panels. Very
large panels are heavy and difficult to lift unless handles are built
in. A panel cannot be keyed out, but I think this is a fairly minor limitation,
since it is possible to stretch a canvas adequately without keying out.
If the canvas has not been stretched enough it should be re-stretched.
It can then be left alone. In future if there is relaxation of the canvas
it can also be re-stretched but the relaxation will be kept to a minimum
by the original low tension and the absence of repeated keying out. However,
a panel does alter the appearance of the canvas painting from the reverse
and changes its character fundamentally.
Blind stretchers
Blind stretchers with panels inserted between the members have a history longer than double canvases. Some of these objects are beautifully constructed and they combine the advantages of the stretcher and the panel. But they do not appear to prevent cracking and the repeated keying out that is possible contributes to cracking and corner draws.
Stretcher bar lining
Many paintings are wanted for exhibition and loan. They need to travel, to be handled and perhaps to be exposed to different environmental conditions. A technique devised at Tate is called stretcher bar lining (previously known as a cami-lining in some literature).19 This involves using polyester sailcloth to provide a support, but in this case attaching the polyester to the reverse of the stretcher using staples along the reverse of the outside members and feeding the polyester under the stretcher cross-members to create a tensioned structure in which the lining is in contact or near contact with the original only at one point in the middle of the canvas. Tensioning the stretcher in this way produces a very rigid structure and the conservator needs to be careful not to pull too hard and remove or distort the tension in the original canvas.
The main value of this technique may not be immediately
apparent but when the canvas is vibrated it becomes clear. Most old cracked
paintings have cracks corresponding to the stretcher inside edges, in
part attributed to the flapping of the canvas against the stretcher. Loss
of tension, through relaxation (or creep), may play a role in this cracking
as does the hygroscopic effect of the stretcher. But when a painting travels
it is subject to repeated forced vibrations at a level and frequency that
is close to its resonance, which will fall in a range of 10-20 Hertz.
By preventing any movement at the middle of the painting the natural frequency
is raised to about four times its original frequency, usually clear of
the main input from a vehicle. The stretcher bar lining is applied continuously
across the back of the canvas and the trapped air creates an air dam that
absorbs the energy of vibration. The effect needs to be seen to be believed
but it is very impressive.
A great advantage of the stretcher bar lining is
the speed with which it can be applied (fig.6). With practice it can be
done in fifteen minutes and removed in five, depending on the number of
staples. It is entirely reversible and preserves all aspects of the original
stretching. We use it on many canvases to make them suitable for loan
and transport and it normally remains in place for the next time the painting
is moved.
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Fig.6 A polyester sailcloth stretcher-bar lining stiffens the structure and prevents the canvas from vibrating in transit. © Tate |
De-lining
Removing an old glue lining is not without its risks and is very time consuming. We do it very infrequently, not least because it begs the question, what should we replace it with? If we consider that the lining was not necessary then the prospect of returning the painting to an unlined state is enticing, but it may be difficult to assess just how good a state the original canvas is in.
For paintings that have suffered serious lining
damage in the past we might like the idea of reversing the damage. We
can take off an old lining but it is unlikely that we can repair flattened
impasto or emphasised canvas weave. If the lining is stable we should
accept that it has become part of the object’s history. If the lining
tacking edges are beginning to fail, we can remove the canvas and glue
for about 25mm width around the perimeter of the canvas and strip-line
the lined painting.
De-acidification
Most of the treatments discussed so far are physical interventions, but we must not forget that the deterioration of cellulose is predominantly a chemical process.20 Essentially, in the light cellulose is oxidised by air and in the dark it is hydrolysed by water vapour. The oxidation process creates acid groups that lower the pH of the canvas creating ideal conditions for hydrolysis. Air pollution also creates acid conditions. Our early attempts to reduce oxidation with anti-oxidants were not successful but the application of alkaline materials to increase pH was very successful, drastically reducing the rate of hydrolysis.
We have been tentatively de-acidifying canvases
now for about twenty years and have not found any un-surmountable disadvantages
to this procedure.21
Several studies have sought to find problems and unwanted side effects,
but as time goes by I am increasingly confident to recommend the process
to others.22 In careful
hands, the application of a de-acidification agent of the Wei T’O type
(magnesium methoxy methylcarbonate in a volatile solvent) appears to be
effective and safe.23
The process reduces the rate of deterioration of new canvas when excluded
from light by an order of magnitude. This is a powerful argument for its
application to all new canvases.
Older canvases are frequently degraded and have
absorbed much sulphur dioxide and other air pollution. Certain fibres
such as hemp and sisal deteriorate very rapidly and become very acid.
Surface pH measurements between 3 and 4 are common. These canvases should
be at least neutralised to stop further rapid decay. Leaving an alkaline
reserve of magnesium ions can provide a period of respite before the process
accelerates again.
We are also beginning to go back to the oxidation
problem. We are currently testing enclosures for works of art on paper
that will be air-tight and will allow us to exclude oxygen. If this is
successful it could be extended to some painting canvases.
Conclusion
Now that paintings are rarely lined it is difficult for a conservator to obtain practical experience of different types of lining. This means that the current generation may have to make decisions based on published studies, which may not give enough information to establish a balanced account of the benefits and disadvantages. Practical studies are likely to include the perceptions and pre-occupations of the conservators reporting on their work. Detached scientific studies of lining processes may not be able to take into account the full nature and range of the paintings that are under consideration. It is important to look at all the literature and not to come to conclusions too quickly about one solution or another, and to retain a range of possibilities for action.
Conservators have only a few reliable solutions
to the complex structural problems that occur on paintings on canvas.
In the past we have responded too late and too heavy-handedly to structural
deterioration, sometimes creating more problems than we have solved. In
the last thirty years we have seen a revolution in our understanding and
have adopted methods that are far more considered and less interventionist.
Improved understanding of paintings on canvas has
given us new ways of assessing the effectiveness of any treatment, but
it does not prevent the need for ethical decisions. To help decide in
a particular case, we can define a number of hierarchies: the degree of
intervention that is acceptable, the likely success of any treatment and
the seriousness of any negative side effects. These are dependent on the
use to which our painting is to be put and the environment to which it
will be exposed.
In general, we should like to preserve the nature
of the object, the artists’ techniques and the original technology, but
we need to make sure that the painted image is presented well and that
the painting can be displayed, loaned and stored safely. We do not want
to have to return to carry out further consolidation, although with under-bound
paintings this is frequently the case. Increased confidence in the outcome
of treatments means that we are willing to intervene less. Confidence
in the behaviour and impact of the environment is also critical: for instance,
creating a micro-environment around a painting within a glazed frame is
so successful that even wood panels do not flake.
In a conservation timescale the changes in our
understanding have been rapid and dramatic. Ideas have changed much more
rapidly than our individual conservation treatments last. We have gone
from a position of skilful but unthinking practice to one of much better
knowledge.
As a result of this new knowledge in some areas
we need to reconsider our ethics, many of which have been superseded by
events. More subtle solutions are now available and we can analyse the
forces and reactions involved. But our solutions are only as good as the
accuracy of our predictions. In particular, our ability to intervene chemically
and the implication that this is best done while the canvas retains some
strength challenges the simple notion of minimalism.
Notes
1. Stephen Hackney, ‘Reline, Line, Deline’, in Mary Bustin and Tom Caley (eds.), Alternatives to Lining: Structural Treatment of Paintings on Canvas without Lining, UKIC, 2003, pp.5-8.
2. Caroline Villers (ed.), Lining Paintings: Papers from the Greenwich Conference on Comparative Lining Techniques, Archetype Publications, 2004.
3. Vishwa Mehra, ‘A Low Pressure Cold-Relining Table’, in Caroline Villers (ed.), Lining Paintings: Papers from the Greenwich Conference on Comparative Lining Techniques, Archetype Publications, 2004, pp.121-4.
4. Gustav Berger and William H. Russell, Conservation of Paintings: Research and Innovations, Archetype Publications, London, 2000.
5. Westby Percival Prescott, ‘The Lining Cycle’, in Caroline Villers (ed.), Lining Paintings: Papers from the Greenwich Conference on Comparative Lining Techniques, 2004, pp.1-15.
6. Bent Hacke, ‘A Low Pressure Apparatus for Treatments of Paintings’, in ICOM Committee for Conservation, 5th Triennial Meeting, Zagreb, 1-8 October 1978, ICOM, Paris, 1981, 81; 2; 2-13.
7. Alan Cummings and Gerry Hedley, ‘surface Texture Changes in Vacuum Lining: Experiments with Raw Canvas’, in Caroline Villers (ed.), Lining Paintings: Papers from the Greenwich Conference on Comparative Lining Techniques, Archetype Publications, 2004, pp.87-95.
8. Stephen Hackney, ‘Texture and Application: Preserving the Evidence in Paintings’, in Victoria Todd (ed.), Appearance, Opinion, Change: Evaluating the Look of Paintings, UKIC, 1990, pp.22-5.
9. Paul Ackroyd, ‘The Structural Conservation of Canvas Paintings: Changes in Attitude and Practice since the Early 1970s’, Reviews in Conservation, no.3, IIC, 2002, pp.3-14.
10. Stefan Michalski, ‘Paintings - Their Response to Temperature, RH, Shock and Vibration’, in Marion Mecklenburg (ed.), Art in Transit: Studies in the Transport of Paintings, National Gallery of Art, Washington D.C., 1991, pp.173-90.
11. Marion Mecklenburg, ‘some Aspects of the Mechanical Behaviour of Fabric Supported Paintings’, Report to the Smithsonian Institution, Washington, D.C. , 1982, unpublished typescript.
12. Christina Young and Paul Ackroyd, ‘The Mechanical Behaviour and Environmental Response of Paintings to Three Types of Lining Treatment’, National Gallery Technical Bulletin, no.22, 2001, pp.85-104.
13. Gerry Hedley and Caroline Villers, ‘Polyester Sailcloth Fabric: A High Stiffness Support’, in Norman Brommelle and Gary Thomson (eds.), Science and Technology in the Service of Conservation, IIC, 1982, pp.154-8.
14. Alan Phenix, ‘The Lining of Paintings: Traditions, Principles and Developments’, in Lining and Backing, UKIC, 1995, pp.21-33.
15. Simon Bobak,‘The Limitations and Possibilities of Strip-Lining’, in Mary Bustin and Tom Caley (eds.), Alternatives to Lining: Structural Treatment of Paintings on Canvas without Lining, UKIC, 2003, pp.15-20.
16. Winfried Heiber,‘The Thread-by-Thread Tear Mending Method’, in Mary Bustin and Tom Caley (eds.), Alternatives to Lining: Structural Treatment of Paintings on Canvas without Lining, UKIC, 2003, pp.35-48.
17. Elisabeth Bracht, ‘Barnet Newman’s Cathedra (1951): Restoration of Slash Damages in a Colourfield Painting’, in Mary Bustin and Tom Caley (eds.), Alternatives to Lining: Structural Treatment of Paintings on Canvas without Lining, UKIC, 2003, pp.21-8.
18. Stephen Hackney, ‘Framing for Conservation at the Tate Gallery’, The Conservator, no.13, UKIC, 1990, pp.44-52.
19. Timothy Green, ‘Vibration Control: Paintings on Canvas Supports’, in Marion Mecklenburg (ed.) Art in Transit: Studies in the transport of Paintings National Gallery of Art, Washington, 1991, pp.59-67.
20. Stephen Hackney and Gerry Hedley, ‘Measurement of the Ageing of Linen Canvases’, Studies in Conservation, no.26, 1981, pp.1-4.
21. Stephen Hackney and Torben Ernst, ‘The Applicability of Alkaline Reserves to Paintings on Canvas’, in Preventive Conservation Practice, Theory and Research, Ottawa IIC Congress, 1994, pp.223-7.
22. Adriana Rizzo and Aviva Burnstock, ‘A Review of the Effectiveness of the De-acidification of Linen, Cotton and Flax Canvas after Seventeen Years of Natural Ageing’, in Mary Bustin and Tom Caley (eds.), Alternatives to Lining: Structural Treatment of Paintings on Canvas without Lining, UKIC, 2003, pp.49-54.
23. Stephen Hackney, Joyce Townsend and Nicolas Wyplosz, ‘studies on the Deacidification of Canvas Supports with Magnesium Methyl Methoxycarbonate (MMC)’, Pre-prints of Edinburgh Conference, ICOM Committee for Conservation, 1996, pp.271-5.
Acknowledgements
I am grateful for the support of the Leverhulme Trust
which has funded research at Tate on the mechanical properties of canvas
paintings (1997-2001) and to colleagues, conservators and researchers,
at Tate and elsewhere, who have addressed these issues over the years,
notably Mary Bustin for her role in the recent Alternatives to Lining
conference.
Stephen Hackney is Head of Conservation Science at Tate.
Tate Papers Autumn 2004 © Tate
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