From Discolored Varnish to Smoke Damage: How Conservators Clean Oil Paintings
Every treatment is unique, but cleaning an oil or acrylic painting often involves removing dust, dirt, varnish, cigarette smoke, soot, accretions, overpaint, mold, mud, insect debris, and more with both mechanical and chemical approaches. Paintings might benefit from cleaning after a disaster (fire, flood, mudslide, etc.), years of neglect, regular exposure to the elements, accidental damage, and even vandalism.
For example, I once removed lipstick from a painting that had been "kissed" by a guest while exhibited at a gallery. Another time, I removed food splatter from a painting that hung in a high school cafeteria. Continue reading to learn how conservators clean paintings (including what cleaning materials and techniques we use) and why cleaning your own painting at home might not be as safe and straightforward as it seems.
How Conservators Clean Paintings
Before cleaning any painting, conservators examine the recto, verso, and tacking edges with visible light, UV, and magnification to assess its condition. We also conduct a variety of tests to determine what sits on the surface, has embedded itself, or has eaten away at the painting (e.g, dirt, accretions, dust, smoke, soot, coatings, etc.). During this phase, we might also test certain pigments we suspect might be unstable when exposed to solvents, chelating agents, or even moisture. We take detailed notes and photographs.
"Dry" Cleaning and Mechanical Methods
A frame with accretions in the upper right of the top frame member; the accretions were removed mechanically.
Once given permission to treat a client's painting, we start with dry cleaning methods—like using a very soft brush to gently brush away loose dust into the nozzle of a vacuum cleaner or removing soot with smoke sponges. Tools like scalpels, tweezers, and even dental instruments are used to remove accretions, varnish trapped in impasto, and other areas that need detailed attention under the microscope.
"Wet" Cleaning Methods
We then proceed with wet cleaning methods if necessary. Wet cleaning methods might involve solvents, solvent gels, chelating agents, and/or moisture. We often formulate our own solvents, gels, and chelating agents at varying concentrations to ensure they are effective without damaging the paint layer.
These solutions and gels are used to remove dirt, accretions, stubborn stains, adhesives left behind by labels and framing paper, fly specks, varnishes, other coatings, and much more. Oftentimes, we switch back and forth between chemical and mechanical cleaning methods until satisfied with the results.
Regardless of the treatment, we always adjust pH levels, solvent concentrations, and application methods as necessary to ensure the paint layers remain stable throughout the cleaning process.
Answering Your FAQs About How to Clean a Painting
Can I clean my painting myself?
No, we do not recommend that you clean a painting yourself. Even minor cleaning attempts can inadvertently damage the paint layer, varnish, or canvas. Paintings with high or thick impasto are particularly at risk of damage because their peaks can catch materials used in cleaning (e.g., the weave of a white cotton cloth or the hairs of a brush). Even with the gentlest touch, you might break hardened paint that has become brittle over time.
Can I remove the varnish on my painting by myself?
Again, we do not recommend trying to remove the varnish or coating on your painting (whether it is an oil painting, acrylic, or mixed media) because varnishes do not react reliably to solvents. For example, many artists formulate their own coatings or use unsuitable materials that react poorly with the paint layer(s). This can make removal more complicated. Even a properly formulated varnish that is of the appropriate opposing polarity to the paint can degrade and crosslink over time.
Is it safe to clean my painting with a white cotton cloth soaked in warm water?
No, using a damp cloth—even a clean white one—can cause serious damage to the painting. Moisture can disturb the varnish or paint layer, leaving streaks, discoloration, or worse—causing paint to lift, tent, dissolve, or crack.
Again, some pigments bound in oil react with moisture. Trying to clean an oil painting with a soft cloth can also cause accretions, splatter, and debris to partially dissolve and drag across the image area—resulting in paint loss, abrasion, and more.
It’s best to leave all cleaning to a professional conservator. When we clean an oil painting, we do not use rags to gently wipe away dust, dirt, or soot; instead, we use sponges and other implements that are easy to direct. If using moisture, we use a cotton swab—not a cloth.
What could happen if I do clean my painting at home?
Even "gentle" cleaning solutions like plain water, mineral spirits, or a mild soap solution can cause damage to paintings if applied incorrectly. If you try cleaning your painting at home, the following could occur:
Abrasions or scratches to the surface.
Spreading of mold, mildew, or soot to other areas of the painting.
Partially removing, discoloring, or "blooming" the varnish.
Creating cracks in the paint layer.
Causing losses after catching lifted, tented, or otherwise unstable paint.
Further fracturing friable paint.
Solubilizing unstable pigments.
Disturbing under-bound paint (loose particles that appear soft and diffuse); even a few drops of a solution can cause damage here.
Removing inscriptions made by the artist, framers, or gallerists that are important for provenance.
Introducing moisture or chemicals that weaken the canvas or wood structure.
Creating undulations in the canvas by applying too much moisture (if this occurs, allow the painting to air dry completely before moving it).
Rusting tacks or staples due to moisture exposure.
Solubilizing under-drawings or ground layers.
Leaving behind residues that attract dirt or chemically react with the paint or varnish over time.
Inadvertently embedding dirt.
Over-cleaning the paint layer while using a varnish remover or cleaner.
What should I do if my painting looks dirty or discolored?
If you notice dirt, discoloration, or dullness, consult a professional conservator (sometimes called a professional art restorer, though these terms are indeed different). They will assess whether the surface needs cleaning, varnish removal, or other conservation treatments. In the meantime, avoid wiping or dusting the painting with household materials like paper towels or cloths.
Can I dust my painting?
If you feel absolutely confident that your painting is free from abrasive surface dirt, soot, cracks, flaking paint, loose pigments, or accretions that could scratch the painting during removal, you can lightly dust using a very soft, dry brush (like a hake brush). Never use feather dusters, vacuums, microfiber cloth, or compressed air. Always avoid harsh cleaning agents. When in doubt, consult a conservator before attempting any maintenance.
How often should paintings be cleaned?
Paintings generally don’t require frequent cleaning unless stored or displayed in environments prone to dirt or pollutants. A conservator can recommend a maintenance schedule based on the painting’s age, materials, and environmental conditions. We typically suggest having your collection assessed every five years to ten years (or even less frequently) unless an obvious issue emerges.
Is it ever safe to use over-the-counter cleaning products?
No. Household cleaners, soaps, or solvents (like rubbing alcohol) can cause irreversible damage. Even gentle soapy water and similar products can affect the varnish, damage paint, or introduce residues that attract dirt over time.
On Reddit or in other forums, you might read that an "olive oil based soap works wonders" to remove dust and dirty from paintings. This is not accurate. Do not do this. Leave all cleaning to professionals.
What are signs that a painting needs cleaning?
Above is a detail photograph taken under a microscope. The image shows a pale blue-gray acrylic paint layer under a yellowed, resinous coating with multiple accretions trapped between the paint and varnish layer. Unfortunately, the acrylic paint and coating are similar in polarity and are both solubilized by the same solvents. Gels and solvents can be used to soften the varnish before it is mechanically peeled off.
Signs that your painting might benefit from professional cleaning include but are not limited to:
A dull or cloudy surface.
A yellowed varnish layer.
Visible dirt, soot, stains, or smudges.
Loss of vibrancy (this could be due to fading—not dust or dirt).
Mold, mildew, or mud from exposure during natural disasters, storms, placement in a bathroom, etc.
Reduced readability (difficulty making out signatures and/or finer details).
Obvious accretions from pests (rats, mice, spiders, flies, beetles, etc.).
Food splatter or signs of vandalism.
Fingerprints.
Tidelines (either in one area or across the entire canvas).
How can I protect my painting from getting dirty?
Display all paintings (whether oil, acrylic, mixed media, or watercolor paintings) in a clean, stable environment away from air conditioning or heating vents.
Keep paintings out of full baths in which dew point humidity is common (powder rooms may be acceptable).
Avoid direct sunlight, high humidity, and temperature fluctuations.
Do not allow guests or children to touch paintings.
Cover or remove paintings during remodeling or repair work on your home or gallery.
Keep paintings away from areas prone to grease, smoke, or dust like kitchens and fireplaces.
Apply UV-filtering glass to frames or a protective acrylic barrier for added protection against dust, dirt, and touching by guests.
Can I remove mold or water stains myself?
No. Mold and water damage are complex and require specialized treatment to prevent further harm. Attempting DIY fixes can worsen the problem or spread mold spores. Contact a conservator immediately if you spot mold or water stains.
What should I do if my painting is damaged by a flood, fire, or other disaster?
The above painting was covered in mud during a mudslide. We carefully removed the mud and rusted staples, but the mud had eaten away at some of the canvas (shown in lower left).
In the event of a disaster:
Do not attempt to clean the painting; specifically, do not try to remove mud or soot. Soot contains particulate matter than can drag across the painting's surface and cause damage. Mud can erode canvas and might create tears if removed improperly.
Do not try to take the painting out of its frame.
Take care when lifting the painting as damage might not be immediately noticeable.
Place it in a safe, dry environment away from direct sunlight or heat sources.
Contact a conservator immediately for advice, examination, and treatment options.
Why is varnish removal considered part of cleaning?
Varnish removal is not always necessary and is not always part of the cleaning process. Varnish can yellow or discover over time—depending on the type of coating, environmental conditions, exposure to cigarette smoke, etc. It can imbibe dirt, dust, smoke, and more. Only trained conservators should perform varnish removal and reapplication. Reapplication will not always be necessary.
I’m an artist. Can I clean my own artwork?
Even artists should exercise caution. Over time, varnish, dirt, and other environmental factors can interact with the materials in ways that require professional expertise to address safely.
How can I find a qualified conservator?
Look for conservators associated with organizations like:
American Institute for Conservation (AIC)
International Institute for Conservation (IIC)
Northern States Conservation Center
We follow strict ethical guidelines, have the training to handle your paintings with care, and contribute to the industry by teaching other professionals. Bear in mind that conservators (unlike restorers) typically specialize in a specific object type. For example, I only treat paintings. Other conservators only treat objects.
