Glazing With Oils
Glazing with oils can be a very tedious process. One has to be very patient and allow each layer of glaze to dry thoroughly so the layers won't blend or merge with one another. Also, a glaze painting must be placed on a proper foundation or the life of the painting and array of glazing effects will be greatly altered.
BASE or SUPPORT:
A good base for supporting a glaze painting is wood. A wooden panel (of any good acid free hard wood) cut very thinly makes a very good base. The old masters created many paintings on wooden panels.
In today's market, and with the present technology in the press board manufacturing, we can find many good supporting materials. Be cautious of the inconsistency of cheaply made pressed wood products as sometimes the binding material is not evenly distributed within the panel. This can lead to chipping or bubbling. Masosnite panels is one of the finest to use. The name Masonite is a trade marked name for a specific product that is created by using steam to form the particles into boards without the use of additive glues. Unfortunately in many instances, the inferior cheap boards are referred to as Masonite panels.
Canvas, especially linen is very flexible and changes or sags according to the moisture in the air. In my opinion, this alone makes canvas one of the least desirable supports for use in the art of glazing.
Preparation can be accomplished using either fine art oil underbase paint or finely ground Gesso. Whether canvas or wood, the support must be properly prepared to accept the layers of paint glazes and should be of good quality material that will remain very stable throughout the life of the painting. Atmospheric and temperature changes can affect glaze painting...or any other painting. When coating a surface to accept a glazing, I use two methods of preparing my surfaces. One is with a fine brush and the other is spraying a smooth coating. Either technique can be used whether you are preparing with oil underpaint or Gesso.
BRUSHING: I usually apply a fine, art grade Gesso in a thin and consistent coating, brushing in one direction only. If I wish to obtain a canvas look to the surface I wait for the first coating to dry, then lightly sand with an 800 grit wet-or-dry paper and then apply another coating of Gesso on top of the first layer in the opposite direction. This creates a canvas look similar to fine linen.
SPRAYING: Use a fine spray unit and paint three smooth coatings on the board, sanding lightly between each coating. This gives good adherence to each coat and the end result is a smooth surface for glaze painting.
OIL PAINTING MEDIUMS:
Oils used in oil paints are considered "drying oils" and are selected for this reason. Other oils that are not drying oils are used for lubrication and not selected for paint making A few examples of oils used in fine art painting are listed below.
Linseed Oil (Cold Pressed), Usual ingredient in oil paints and works well as a medium. Does yellow with age.
Sun Thickened Oil, made from linseed oil, enhances gloss of paints, increases transparency and accelerate drying time of paints.
Stand Oil, (one of my favorites) Very similar to Sun Thickened oil and is a good medium. Excellent gloss and drying hardness. does dry with a shiny surface film however so must be lightly rubbed so that it will not repel the next layer of glaze. Does not yellow and adds to the smooth flow of glaze.
Poppy Seed Oil, Slower drying oil than the oils made from linseed but is weaker and softer oil in the area of film forming. Can become rancid.
I like to mix my own mediums for glazing. Below are three that I have concocted over the years and I use them in my work. In some of them I use Copal Concentrate. Natural Copal is a natural resin such as amber and is very scarce. However modern versions of copal in synthetic form are available. Copal slows the yellowing of oil paints and creates a flexible film that resists becoming brittle with age. Refer to the callouts in each image to see the correct amounts of each ingredient.
If I need a medium to dry a bit faster, I add only a few drops of Cobalt Drier.
Medium Mix #1
Medium Mix #2
Medium Mix #3
There are many oils available that can be used as painting mediums. Stand oil (a derivative of linseed oil) has been used by glazing masters for years. It is made by treating the linseed oil with heat until slight polymerization begins to occur. The result is a thick, pale to light amber liquid that can be thinned with rectified turpentine or rectified petroleum thinner to the proper consistency. Stand oil should be thinned in most cases because it is difficult to use in its natural, thick state. Then thinned, Stand oil improves the gloss and flow of the paint and produces a flexible but tough film that is superior in resisting yellowing and cracking with age. In my opinion, stand oil is one of the best mediums for painting; it is especially good for glazing because the oil flows so beautifully that it lays down smooth and when dry, can hide any trace of brush marks.
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