How to clean an oil painting

All oil paintings are different from each other and each painting must be treated as a unique project. There are similarities but I always treat them a new item. They can vary so much because of many different factors such as the medium they are painted in, the varnish used, the type of dirt and contamination it has been exposed to etc.  Having restored over 2000 paintings over the last 20 years I have learnt to never assume anything always be cautious and expect the unexpected.

Before any  cleaning can take place in the painting must always be stabilised. Sometimes it already is and you can commence cleaning straight away, but more often than not. There will be some work to be carried out whether that be cracked paint a tear in the canvas strip lining, completely re-lining. Once stabilising is complete, and you are ready to clean the first thing you must do is test what solution/solvent/cleaning agent needs to be used to get the best results without damaging the painted surface.

I, in most cases, find it better to remove the dirt first before attempting to remove move the varnish. This prevents the need to use too much solvent which can have a damaging effect to the paint. Particular care should be taken when moving from one colour to another as some paints are more susceptible to breaking down than others. For example, reds seem to be more likely to break down, largely due to iron oxide in the paint pigments, this causes the paint to have a high conductivity.

Once you have removed the dirt a polar solvent with a none polar solvent mixed with reference to the tests carried out can be used to remove the varnish with an appropriate cue tip. A pure none polar solvent should be used to remove the residue before it re-hardens.

After the cleaning process is finished an isolation varnish can be added to saturate the paint colours allowing any in-painting to be successfully colour matched.

If your painting has value, monetary or sentimental you are always better to seek a  professional to do the work for you.