Archive · 31 Jul 2025
Old Oil Paintings Suffer Chemical 'Acne' and Conservation Efforts
Imagine paintings getting a case of acne years after they're finished.
This is happening because of a chemical reaction in the paint called saponification.
Metal ions in the paint mix with the oil and cause soap-like blobs and drips.
Changes in how paint is made, like using different oils, have made this problem worse.
Scientists and museum experts are trying to figure out how to clean and care for the paintings without making them worse.
They're looking at things like cleaning solutions and the amount of moisture in the air to protect these old masterpieces.
Oil paintings are experiencing 'metal soap' formation, causing damage like pimples and drips.
The issue is linked to metal ions in pigments reacting with fatty acids in the oil.
Changes in paint formulation, like the use of substitute oils and zinc-based pigments, have increased vulnerability.
Museums and conservators are researching cleaning solutions and humidity control to mitigate damage.
Solutions are being sought to preserve the artwork and the costs of maintaining the artwork.
- Who
- Art conservators, scientists, and museum professionals are studying and addressing the problem.
- What
- Oil paintings are experiencing damage due to a chemical reaction that creates metal soaps, resulting in pimples, drips, and other imperfections.
- When
- The issue occurs over time, sometimes decades after a painting is created.
- Where
- The damage is observed in oil paintings in museums around the world.
- Why
- Metal ions in the paint react with the oil, causing the damage.
Perspectives on Cleaning
Balancing Action
Cleaning Solutions
Perspectives on Cleaning
Some researchers worry that cleaning solutions could penetrate paint layers and accelerate the damage.
Balancing Action
Other conservators might accidentally remove material deliberately placed there by an artist.
- Culprit
- Metal ions in paint pigments
- Reaction
- Metal ions react with oil's fatty acids
- Result
- Formation of metal soap
- Affected Works
- Paintings by Rembrandt, Georgia O'Keeffe, and others.
- Percentage Affected
- 70% of oil paintings in museum collections
- Conference
- Rijksmuseum in Amsterdam