With the Art of the Portrait Conference soon approaching, I am put in mind of the last minute preparations all artists make before the hanging of their paintings in an exhibit. Historically, before large shows at the British Royal Academy or at New York's National Academy, artists were given a "Varnishing Day" on which they could apply a final coat of varnish to their works before the opening, or make some last minute corrections. Some artists like J.M.W. Turner were famous for submitting nearly blank canvases for the exhibitions, and actually painting the majority of their work on Varnishing Day! For those getting their paintings ready for display, here are some suggestions on varnishing as put forth by Hilaire Hiler in his book, Notes on the Technique of Painting.
To make a good job of resin varnishing is not easy. If you feel that you are unable to do it, and care a great deal about the picture which is to be treated, it is better to leave it to a good specialist if you can afford to pay him. I have seen painters of many years' experience do almost irreparable harm to their pictures by bad jobs of varnishing. In using resin varnishes the following rules must be observed in order to get the best results.
1. Have your varnish warm, and your diluent also, if you wish to dilute it. If you are diluting with turpentine, be sure of the nature of your varnish before doing so, or it may behave badly or bloom. Genuine mastic varnish does not bloom through being diluted with turpentine.
2. The picture to be varnished must be scrupulously clean. Rudhardt advises rubbing the surface with half a raw potato, and then carefully rinsing it with tepid water. It must be allowed to dry thoroughly, and should be gently warmed, to make sure that it is absolutely dry. It may then be coated with purified petrol and varnished immediately afterwards, if you are sure that the petrol will have no bad effect on the resin you are using.
3. Varnish must be kept clean and dry in well-corked receptacles. It must be poured only into clean dry vessels, and from these never back into the main receptacle in which it is kept, if it has been in contact with the brush. Use for varnishing only perfectly clean dry brushes which are not moist with oil of turpentine, linseed oil, or varnish.
4. Always apply in thin coats as evenly as possible. Spirit varnish should be applied quickly and daringly without going over. Oil varnish, on the contrary, can be worked up and smoothed out, which only serves to improve it. When you lay an oil, varnish with a flat varnish brush from left to right and from right to left; from top to bottom and from bottom to top; cross everywhere and rapidly work out an bubbles. This of course should be done with the picture lying flat.
5. Like all oil-paint coatings, every coat of varnish must be thoroughly dry before a new one is put on; otherwise cracks may ensue.
6. Never varnish on a damp day.
7. The varnish must be dried in a warm place, and the surface varnish thoroughly protected from dust. A spare-room which is used for nothing else is ideal to put pictures in to let them dry. If this is not possible, turn the painting face downwards over a very clean and freshly oiled or waxed portion of the floor. It may be supported on two chairs, trestles, boxes, etc., covering the whole thing with an old sheet, or other clean cloth, which should of course reach close to the floor.
8. Stir and work up varnish well before applying.
9. Never expose modern varnishes to the sunlight to dry.
10. Have a brush which is just right. This is of primary importance. A brush which still holds the split points of the bristles never varnishes clear; they are rubbed off easily and spoil the varnished work. A brush which has never been used does not produce clean work; it should be tried several times, and when it is found that the varnishing accomplished with it is neat and satisfactory it should be kept very carefully.