Paintings are varnished to protect the paint layer, reducing the risk of damage, as well as reducing the risk of colours fading. You may feel that your varnished painting needs brightening up, or that it has holes and cracks which require a new layer of paint which you can do yourself at home. However, this could have dangerous consequences for the original artwork and is not advised. 

Painting over an antique oil painting, especially when it shows signs of deterioration or dullness, can decrease its longevity. Your painting may require specialist conservation methods and materials in order to prevent any further decay. In these cases, a touch of paint may hinder rather than help an artistic blemish, due to the long term consequences of the damage beneath.

How can I tell if my painting is varnished?

The majority of paintings are varnished when they are finished. There are many types of varnish. Historically, varnish is made of natural tree resin. Today, it is often made of synthetic resin which is less prone to organic decay (this can cause discolouration) and has UV protection. 

There are different levels of varnish, including high gloss, satin and matte. A shiny or light reflective surface will indicate a gloss or satin finish, whilst a duller finish will indicate matte. If you’re unsure whether your painting has a matte finish or is simply unvarnished, 

My painting is dark/dull, should I paint over it?

If your painting is dull, this is likely due to contamination from the atmosphere or the ageing of the original varnish. Both of these issues should be addressed with conservation techniques, to prevent further deterioration, rather than being overpainted. 

A darkened or yellowing painting can be caused by a variety of reasons. These include nicotine staining, historic debris, or smoke from fireplaces. Sometimes these atmospheric contaminants can be harmful and over time degrade the original artwork, so should be cleaned professionally and not covered up with untested homemade techniques. Every artwork has individual needs, so the chemicals required to clean the piece need to be tailored in order to prevent any disruption to the artwork.

The varnish itself may also be the cause, this will need to be replaced with a contemporary conservation-grade varnish which will allow the bright, original colours to come through, whilst protecting it for future generations by preventing UV rays and giving further stabilisation to the piece. 

If your painting is dull in a way which may seem clouded or frosty, this may be caused by blanching varnish. Blanching is when moisture becomes trapped underneath the varnish layer. This will need to be treated with professional techniques to prevent any damage caused by damp or mould.

My painting has missing paint, should I fill in the gaps?

If a painting has gaps where paint is missing and canvas can be seen, the painting is unstable and at risk of further loss of the original artwork. Filling in these gaps with contemporary paint may compromise the artwork further, as it will also be missing parts of its original protective varnish.

My painting is covered in cracks, should I paint over them?

Over time, paintings naturally have a thinly cracked surface. This is called ‘craquelure’ and is not something that needs intervention and should not be painted over, as it is a natural appearance to antique art. 

If your painting is heavily cracked, with the canvas showing through, it is at high risk of paint loss and should be restored by a professional conservator to avoid further deterioration.

Can I use contemporary paint on an old painting?

When paintings are restored a trained conservator will use conservation grade pigments which are carefully colour-matched to the original. These pigments are not permanent, which means that if in future the painting requires a new restoration, these can be taken off and replaced. It also means that the artistic integrity of the original painting is not permanently changed. 

A conservator will only ever retouch the minimal amount needed for the conservation of the work. This means that the over-painting of any losses in the artwork does not alter the work or disrupt its original composition, or artistic and monetary value.