My article on Why Oil Paintings Need To Be Varnished discusses the why of varnishing oil paintings. This present article is concerned, as its title suggests, with the how of varnishing an oil paintings.
Stages Of Varnishing.
There are two stages at which an oil painting can be varnished: as soon as the paint is touch dry and after at least six months following its completion. This may sound contradictory, but the two statements are reconciled in the way and for the purpose that varnish is applied.
Touch Dry Varnishing
The varnish used at this stage is different from that used after the six months limit. It tends to be used by professional artists who cannot afford to have pictures hanging around (no pun intended!) for six months. The kind of varnish used is something such as Daler-Rowney Retouching Varnish . This is applied as a temporary coating to protect the surface of the painting.
The kind of varnish used at the final varnishing stage is one of the many sold specifically for this purpose, such as Artisan Gloss Varnish or Matt Varnish or Satin Varnish depending on the kind of finish you prefer. It must not be applied in less than six months — for safety’s sake, not even over alkyd quick drying oils.
The reason for not varnishing under this period is simply that oil paints do take a lengthy period to dry and if the varnish is used prematurely it will have a similar effect to applying a later coat of oil paint over an earlier one which is not yet fully dry. Just as in the latter case, so vanishing too early will seal the surface of the painting and prevent the earlier oil from drying. You will end up with a more or less permanently wet painting.
Once the painting is dry (and that may take longer than six months if an impasto method has been used), it is advisable to gently wipe the surface with a soft cloth to remove any dust. In what follows be careful not to apply the varnish too thickly. To apply the varnish use either an aerosol or a brush. If using a brush it is generally better to use a larger than a smaller one since it will cover a greater wit with each stroke and make the tendency to miss areas between strokes less likely. The overall covering will also tend to be smoother. The actual weights will obviously depend on the size of the painting. Try not to rush back and forth but Labour varnish on as swiftly as possible. Periodically hauled the painting horizontally towards the light to ensure no area is missed. Lay the painting flight on to dry to ensure the varnish does not run.