If we were asked to name one treatment that is carried out most often in the studio, it would be surface cleaning an oil painting. It is by far one of the most common and interesting processes of art restoration, and is completed for almost every oil painting we receive.

Surface cleaning can make a huge difference to your painting. It can reveal hidden details that have been covered by nicotine staining or revive faded colours where everyday dirt has settled on a painting.

That’s why it’s so important to get right and to give you all the information you need about this part of the process. We’ve put together some frequent questions we are often asked about how to surface clean an oil painting. Take a look below, and if you have any of your own, please do get in touch and we will answer your cleaning query.

How to clean an Oil Painting - Before & After

When should I get my oil painting cleaned?

The answer to this question differs for every painting and the environment it has been displayed in. If, for example, a painting has been above a fire for many years or in a room with a smoker then it is highly inevitable that it will benefit from a thorough clean. If you have recently acquired a painting and are unsure of its history, it may be harder to know how it should look without being able to refer to how you remember it. If you suspect it may need surface cleaning, look closely at the lighter colours of the painting, such as white clothing or blue skies. It will be easier to tell if these colours have been muddied. Assessing the back of the painting can also be worthwhile – if you think the front looks okay, but the back of the canvas is very dark, it is likely that the front will be also.

When should I get my oil painting cleaned - before and after

What types of oil painting can be surface cleaned?

Alongside traditional oil paintings on canvas, surface cleaning an oil painting is also possible for those on panel and copper. For copper paintings, it is best to avoid aqueous (water-based) treatments. Using a conservation gel will remove the surface dirt and not risk the painting. For panel paintings, we tailor the treatment to suit the painting and like with paintings on canvas, we carry out the appropriate tests to see what the best cleaning agent will be.

You can read our detailed articles for more information on cleaning oil paintings on copper and oil paintings on panel.

Oil Painting Cleaning

Is surface cleaning different from varnish removal?

Surface cleaning is the process one step before varnish removal. The surface contaminants are lifted and then the intact varnish layer is present underneath. Over time the dirt has settled over the varnish layer and needs to be removed.

Can surface cleaning remove the varnish layer?

Surface cleaning an oil painting will only remove the dirt sitting on top of the varnish layer. This is removed first and then the old varnish is removed subsequently. Different materials are used for cleaning and then for the varnish removal.

An oil painting being cleaned by the Fine art restoration company

What is varnish removal?

Following surface cleaning, varnish removal is the next step. The original varnish layer often becomes discoloured and the traditional resin varnishes become yellowed. If the varnish layer is particularly thick and yellowed then it can obscure the details of the painting and original colours. If you are unsure whether the yellowing is caused by environmental factors such as nicotine or smoke, or is due to the varnish layer, we can take a look for you via photographs and provide our free advice.

Removing the varnish layer can greatly improve your painting and return it to its original condition and colours as intended by the artist. This can be completed in much the same way as surface cleaning, completing tests by applying solvents, solvent mixtures or alternatively gels and seeing which can best remove the varnish layer. The test windows are important as each painting has a different varnish and also different paint layers.

Varnish removal should not be attempted at home. Without a comprehensive assessment of your painting and understanding of many complex variables such as the stability of the paint layer and whether the painting has any past retouches, it is not possible to know the condition of a painting and how it will react.

It is also imperative to wear the correct PPE (Personal Protective Equipment) including gloves and face respirator and adequate ventilation must be available.

oil painting varnish removal

What do you use to clean oil paintings?

You may have seen from online research the many different suggestions for cleaning an oil painting. From bleach to water, we have been asked our opinion for using a variety of unsuitable methods that will only cause more harm to a painting. The honest answer is that every painting is different and it is only once it has been assessed in person by a conservator that it is possible to understand what the best cleaning agent will be. These solutions can be aqueous (ie containing water-based elements) which need to be carefully controlled.

This can only be determined after conducting small test windows on different parts of the painting. The reason for this is that different pigments are used for the colours, and sometimes different types of paint can also be used. In the below example, the painting is severely nicotine stained. The painting was also severely abraded and different types of paint had been used – possibly water-based.  After carrying out a couple of test patches, we found the most appropriate cleaning agent to carefully lift the dirt. After firstly removing past retouches, we were able to gently proceed. As you can see, the results are excellent.

cleaning an oil painting - before

cleaning an oil painting - after

Cotton swabs are always used as they provide a thorough, safe and even clean. The same results could not be achieved if you cleaned your painting with bread although in the past we have been asked…

Can I clean my oil painting with bread?

This is a strange myth but not a viable option for cleaning an oil painting. It doesn’t contain the right properties for removing dirt and will only leave a residue which will possibly stain your painting, and attract pests and mould growth. If your painting has impasto (when the paint layers are built up so the paint is dimensional and thick) then using something as impractical and relatively rough as bread risks damage to the paint layer.

My painting has flaking paint – can it still be cleaned?

If the paint layer is flaking and causing losses, cleaning needs to come second to consolidation. The flaking paint firstly needs to be stabilised so the paint layer is completely secure and then cleaning can happen. If you clean a painting without first treating the flaking paint, it’s likely you will cause more damage by lifting away the delicate original paint.

Can the back of my painting be cleaned?

Absolutely – just as the front of a painting collects dirt and contaminants, so does the back. This can especially be the case if a painting has been stored in a shed or garage where there are many insects and pests, and the back of the painting can look quite unsightly with dust and cobwebs. If the front of a painting has been exposed to smoke, nicotine or dirt then naturally the back (and also frame) will have likewise been exposed. A smoke sponge or soft bristle brush and museum vacuum are often used to clean the back of canvas – the pressure applied will not cause damage to the front of a painting.  A soft-bristle brush will also be used to remove the dirt from behind the stretcher bars.  It is important to remove loose objects such as dirt and nails as well as occasionally unusual items trapped in this space between the stretcher bar and canvas. Removing any objects here will also take away the risk of distortions being caused on the painting where materials are pressed into the canvas.

Cleaning the back of an oil painting

Can you clean contemporary paintings?

Depending on the age of your contemporary painting and the environment it has been kept in, some modern artworks may benefit from a clean. If a painting was only created in the past couple of years and kept in a suitable clean environment, there will probably not be a substantial accumulation of surface dirt. For an older contemporary painting that may have been in storage, or again kept in a smoky room, surface cleaning can achieve notable results. Our approach will be the same; first completing the relevant cleaning tests and then seeing which is the most effective in lifting the dirt.

Cleaning a contemporary oil painting

Will surface cleaning an oil painting damage the paintwork?

This is an understandable concern for many private clients who enquire into the cleaning of their painting. As we mentioned, surface cleaning is one of the most frequent treatments we carry out and it is not harmful to the painting or the paint layer. The tests we carry out determine what is suitable to use on the painting and the cotton swabs used will not cause any damage. We do not need to press into the painting to take off the surface dirt, so the paint layer will not have unnecessary pressure applied to it. This is especially important if a painting has impasto and thicker paint – we carefully clean each of the raised areas of paint. When cleaning the back of a painting with impasto, it will be completed on an easel so that it is not laid flat and the action does not damage the raised paint layer.

If you have any questions you would like to ask about cleaning, please get in touch! You can contact us and we will answer your question in this article. You can also watch our ‘How to clean an oil painting’ video. Alternatively, visit our oil painting restoration page for more information about our services.