19^th century painting with yellowed varnish and paint loss to centre; below, during repair and filling of losses, dirt and varnish removal.

The same painting following varnish removal and restoration.

Restoration, retouching, or ‘in-painting’, as it is often referred to, is carried out to areas of paint loss, after filling and texturing the surface of the fillings as necessary. Unlike restorations in the not too distant past, today’s approach is much more minimal, avoiding the addition of unnecessary material to the art object. Retouching is usually done using artists fine pigments ground in a medium capable of closely approximating the original paint but without the tendency to discolour.

The application of ‘new’ paint to old paintings is undertaken on top of a thin layer of isolating varnish in order to aid reversibility. The painting is then given a final coat of varnish to produce an even sheen, saturate all colours and provide protection to the paint layer. A range of media could be employed in these processes, depending on the painting.