In the last post I mentioned ‘oiling out’ with a vegetable oil if Liquin or a similar medium is used in a painting. Its a long time since I was discussing this issue so if you are new to this blog you might be wondering why I would recommend this treatment.
I have a page called ‘Varnishing Oil Paintings‘ and its the varnishing which is the kernel of the issue. The manufacturers of Liquin are cautious about varnish being applied to a paint surface containing this product. Windsor & Newton recommend that the uppermost paint layer should not contain Liquin if you intend to varnish. As ‘alls prima’ paintings usually have only one layer the implication is that it should not be varnished if Liquin was used. Unfortunately there is no reason or explanation given by W & N as to the reason for this recommendation. I can only assume its because Liquin will bond with the varnish regardless of how dry it is. My workaround is to ‘oil out’ with a pure vegetable oil, like Linseed or Poppy, which time has proven does not bond with a varnish. This vegetable oil places a barrier between the layer containing Liquin and the varnish.
Remember there are other instances where varnishing causes problems. Low grade solvent, for example hardware grade white spirits or turpentine, can contain waxes or resins. These never fully dry and harden, and solvents in a varnish can dissolve and mix with the paint layer.
All of this is purely academic as the problems occur if the varnish has to be removed, in cleaning the painting, at some time in the future. Paintings under glass will not be subject to the same accumulations of dust or grime as those exposed to the atmosphere. I’ve had to clean paintings and remove old varnish and its impossible to proceed without damaging the painting if some colour is seen in the varnish removed. In these instances I would just remove as much dirt as possible with a damp wad of cotton wool, allow to dry, then use an aerosol temporary varnish to disguise any uneven glossy/dull patches. Reframing under glass will stop any further accumulations of dirt.
Here is the video of the above painting process. See you soon.