Conserving a painting: what can be repaired and what cannot
Table of contents
Oil painting responds to conservation better than any other technique. This is not rhetoric: watercolour, pastel and prints are often lost for good after serious damage, while oil on canvas can be recovered even after a tear.
Here is what can be done with what.
What can be fully repaired
Darkened varnish. The commonest case and the simplest. The conservator removes the old layer with solvent and applies a new one. The painting beneath is unchanged — provided the varnish was of good quality and comes off as intended.
After this treatment a work looks as though it were painted yesterday. That is exactly why seventeenth-century museum canvases do not look their age.
Surface grime. Dust, soot, tobacco film. Removed together with the varnish or separately.
A tear in the canvas. It sounds alarming but is repaired reliably. The conservator lines the canvas — attaching new fabric to the back — then retouches the loss in the paint layer. Carefully done, the join is invisible.
Slackened tension. The canvas has sagged and waves have formed. The simplest case: tap out the keys in the corners or restretch the work.
What can be partly repaired
Cracks in the paint layer. Here it depends on the cause. Fine age crackle is a natural process; it is not removed but consolidated so that the paint does not flake further.
Deep cracks from technical faults — layers built up incorrectly — cannot be eliminated. They are stabilised and retouched, but the structure remains.
Paint loss. Areas where the paint layer has lifted and fallen away. The conservator consolidates the edges and retouches the loss. But retouching is not original painting: it is executed so as to be identifiable under specialist examination, and by the rules it must be reversible.
Water damage. Stains, distortion of the canvas, sometimes mould on the reverse. Mould is removed, stains partly, distortion corrected by restretching. But if the damp stood for a long time, the canvas may have lost strength.
What cannot be repaired
Faded pigments. If a work hung for years in direct sun, some colours have bleached. That is not grime or film — the pigment itself has changed chemically. It cannot be brought back; one can only paint over, and that is no longer the original.
Large areas of loss. If a palm-sized piece of the painting has gone, the conservator can reconstruct it from photographs or by analogy. But it will be a reconstruction, not the original, and the work's value falls accordingly.
The consequences of bad restoration. The worst case. A work once “refreshed” with oil paint over the original, or cleaned with an aggressive solvent that took the upper glazes with it. There is nothing to repair here — the original is already lost.
When to do nothing
Fine crackle. That is the patina of age, not a defect. Museum practice does not remove it.
Slight yellowing of varnish on a warm-toned work. Sometimes it even suits the painting. Varnish is renewed when the yellowing makes the colour unreadable, not by the calendar.
Small abrasions at the edges. If they are not spreading, better left alone. Any intervention is a risk.
A work you do not intend to sell. Conservation costs money and always alters the object slightly. If the painting hangs in your home and you are content — leave it be.
What it costs
Price range for a work of 80 × 100 cm. Prices vary considerably by country and by the conservator's standing.
| Treatment | Cost range |
|---|---|
| Varnish removal and reapplication | €150–400 |
| Retensioning, replacing keys | €50–150 |
| Lining the canvas | €300–800 |
| Retouching small losses | from €100 per area |
| Full conservation treatment | from €800 |
A rule worth keeping: if conservation costs more than half the value of the work, consider whether it is needed.
How to choose a conservator
Specialist training. Painting conservation is its own profession, not the same as being a painter. A good painter can ruin a work while acting with the best intentions.
Experience with comparable works. An icon conservator and a conservator of contemporary painting work differently.
Reversibility of intervention. The founding principle of modern conservation: everything done must be removable without harm to the original. Anyone offering to “refresh” a work with oil paint is breaking this rule.
Photographic documentation. Normal practice is images before, during and after treatment, with a description of what was done.
An estimate before starting. The conservator should examine the work and state scope and cost in advance.
What to do when damage occurs
Do not attempt repairs yourself. The commonest cause of irreversible loss is an attempt to wipe, glue or paint over it personally.
Photograph it. The whole work and the damage close up.
Stabilise the state. If paint is flaking, lay the work flat face up so that fragments are not lost.
Contact a conservator. If the artist is alive, go to him first: he knows the technology of that particular work and can recommend someone.
Frequently asked questions
Does conservation reduce the value of a work?
It depends on the scope. Renewing varnish and minor retouching do not change the value and sometimes raise it. Lining and extensive retouching lower it: buyers on the secondary market look at the proportion of original paint.
Can a work be conserved without documents?
Technically yes. But after treatment authenticity is harder to prove, and without provenance the value is lower anyway. Assemble the documents first, then conserve.
How often is conservation needed?
Under normal storage conditions, once every few decades, and only to renew the varnish. Everything else arises from breaches of those conditions: sun, damp, physical damage.
Can the artist conserve his own work?
He can, and for fresh works that is the simplest route. For old canvases a conservator is better: an artist tends to repaint rather than restore, and that is a different matter.
If something has happened to a work from the studio, write to me before doing anything. I will tell you whether intervention is needed and name a conservator in Warsaw.
