Materials sold in art-supply stores may hold up very well as part of a finished painting, but a great deal of a painting's durability depends on proper handling of those materials, like minimal use of painting mediums and proper varnishing of the finished painting, according to George O'Hanlon, co-founder and technical director of Natural Pigments. O'Hanlon taught a workshop, Painting Best Practices, at Gage Academy of Art in Seattle earlier this month.
This article includes a few highlights from the workshop. A major focus of O'Hanlon's workshop was the use of rigid supports in oil paintings, rather than stretched canvas, which I covered in a separate article. Other topics included grounds, paints, mediums, solvents, and varnishes.
O'Hanlon stressed that an oil painting is a composite, or an object that is made of materials that interact with each other, even after the paint dries. The surface of an oil painting is chemically active for decades. It's unlike any other type of painting, and therefore requires a degree of expertise to use the materials properly.
The three most common types of ground for oil paintings are oil, oil-alkyd and acrylic dispersion primers. All are suitable for use in oil paintings, but the primary white pigment for oil and oil-alkyd grounds should be lead white, rather than titanium white and/or zinc white.
"Lead white is the strongest material in oil paintings, bar none," O'Hanlon said. "If you're going to paint in oil, you've got to paint with lead white."
Most commercial grounds are tinted with titanium white or zinc white, which are less expensive than lead and don't raise concerns of toxicity with buyers. Proper handling of paint and grounds containing lead pigment is not complicated. Grounds and paints that contain lead don't create toxic fumes, so if artists take simple precautions, like wearing latex gloves and an apron, not ingesting their paints or drinking from glasses that once contained painting materials, paints and grounds tinted with lead pigment can be used safely. Lead pigment in its dry state is more hazardous, because it can create dust.
Grounds should be applied in a thick layer, he said. It's an important barrier, especially if painting on a wood panel or panel made from wood fibers, which should also be sealed before the ground is applied.
Paint is made up of a binder or vehicle, like linseed oil or another drying oil; a pigment, an example of which is raw umber; and sometimes a solvent or diluent. Commercial oil paint contains these ingredients plus additives to keep the vehicle and the pigment from separating in the tube. The use of additives changes the character of the paint, making it stiffer, and thus encouraging the artist to use mediums, and often overuse mediums, while painting. This results in a dry paint film that may be weaker than it should be for works of art that are intended to last. Evidence of this problem comes from conservators' efforts to preserve paintings that were created in the past. Paintings made in the 15th and 16th Centuries are, in general, holding up the best, and the quality of oil paintings gradually decreased until the 20th Century, a low point. Materials used had too many ingredients, and were not used properly.
"Paintings from the 1950s and '60s with additives are showing problems," he said.
O'Hanlon's company, Natural Pigments, sells single-pigment paints that contain no solvents or additives. Separation of the oil and the pigment is normal, and the paint can be easily mixed back together with a palette knife, or the oil can be wiped away. O'Hanlon encouraged artists to make their own paint. His wife and business partner, Tatiana Zaytseva, demonstrated the process of making paint at the Painting Best Practices workshop. It involved a simple process of adding drops of oil to a pile of dry pigment, mixing the ingredients into a stiff paste with a palette knife, and then smoothing the paste into soft paint with a glass muller on a piece of lightly textured glass. A slab of smooth stone, like marble, is also suitable.
My fellow attendees at the workshop remarked later at how simple the paint-making process was -- less involved than making cookie dough.
Note: if you can't see this slideshow in your blog reader, visit my website to see it.
If a paint company doesn't list the ingredients on the label, and they won't tell you if you ask, don't use its products, he said.
Lead white also has aesthetic benefits, because as it lightens warm colors, it doesn't cool them down the way titanium white does, and it doesn't neutralize them as much as titanium white does.
O'Hanlon urged professional artists to paint without mediums for the most part. There are times when a medium is appropriate, and the choosing the proper type of medium is important. Oil is a useful medium for certain applications, like glazing, and alkyd-resin mediums can be useful to speed drying, but they are best used as only as a small part of the paint film. Mediums are best used in the final layers of the painting. Earth colors, like umbers and ochres, tend to form the weakest part of paint films if the paint is mixed with a medium to form a glaze. Cracking often occurs in older paintings in the darkest areas, for several reasons, such as a deficit of lead white pigment, and the large ratio of oil to pigments.
"When glazing dark areas," O'Hanlon said, "that's the time to use a resin."
He added that alkyd resin, which is synthetic, is the only resin he recommends for use in oil paintings. Organic resins, like copal, mastic, and damar, should be avoided. Damar and mastic may be used by conservators in museums, but only in special circumstances as a final picture varnish, in spite of the fact that they yellow with age. The artists who used these resins knew this, and made their paintings anticipating the yellowing of the resins in their mediums and varnishes.
He explained why mediums of any type should be used sparingly. Oil paint is chemically and mechanically unlike other types of paint, because no part of the paint evaporates as the paint dries; it polymerizes. The dry paint film contains oil and pigment particles that need to maintain a certain ratio of pigment to oil in order to be strong and stable.
Visualize a brick wall, made up of bricks and mortar. The bricks are the strongest part of the wall, and the mortar functions only to hold the bricks together. If there is too much mortar between the bricks, the wall will be weak. Likewise, the pigment particles are the strongest part of the paint film, and if there's too much oil or medium, the paint film will be weak. A sign of a weak paint film is a dry painting that looks glossy before being varnished.
The most commonly used solvent today is odorless mineral spirits (OMS). It's OK to mix OMS into paint to make a wipe-out underpainting, also known as an imprimatura, he said, as long as it dries fully before the next layer is applied, at least a day. Try to eliminate its use in the subsequent paint layers, and even in brush cleaning. Vegetable oils from the grocery store (soybean oil, olive oil, corn oil, or canola oil) will clean brushes more safely, as long as the brushes are washed with soap and lukewarm water after rinsing in oil. Avoid drying oils when rinsing brushes. Linseed oil, walnut oil, poppy oil, and safflower oil are all drying oils, and could leave your brushes gummy.
OMS fumes are harmful to inhale. Use caution and ventilate the studio with an exhaust fan, not just an open window. Better yet, don't use solvents.
If a solvent is part of an artist's studio practice, the solvents available in an art-supply store are simply higher-priced versions of the products available in hardware stores. Only a few companies manufacture solvents, he said, and they don't alter their formulas for the art market.
Varnish should be applied as a protective coating over dry oil paint, but only when the paint is "hard dry," O'Hanlon said. To test a painting's dryness, stand at arm's length from the painting. Touch your finger to the surface of the painting and rotate your arm, creating a twisting motion on the surface of the painting. Use some pressure against the surface. If the paint moves in response to your twisting motion, the paint is not hard dry. In the event that a painting must be varnished before it's reached the hard-dry stage, its OK to use retouch varnish at the touch-dry stage. Brush-on varnish, both retouch and final, is preferable to spray-on varnish. Final varnish can be applied over dried retouch varnish. Avoid removing varnish with solvent, unless it's necessary, because the solvent will break down the paint, causing the paint film to become more brittle.
He also advises against using retouch varnishes as layers within the paint film, which will be weakened. Oiling out, while not ideal, is preferable for restoring colors and values of dried paint that has sunken in. Oil out by applying a thin layer of oil, then wipe most of it off with a lint-free cloth, like microfiber. One way to prevent sunken-in paint is to be sure the ground is not absorbent, so the paint layer stays put.
He recommended finding an old painting that isn't valuable, and testing commercial varnishes in strips on the surface of the painting, then choosing one of them for regular use.
"Modern, commercial varnishes are all very good," he said, "but they do differ."
Varnishes produce varying levels of gloss on the surface of the painting. Restraint should be used when working with matte varnish. It's best to use only one, thin layer of matte varnish, never more than that. If an artist wants a thick varnish layer, apply a few layers of gloss varnish, then finish with a thin layer of matte varnish. This will prevent a frosty appearance.
Other topics covered in the workshop include paint labeling and studio safety. To stay safe, make sure the studio is well ventilated if or when using solvent, and wear gloves and an apron while painting.
"I do believe in absolute safety," O'Hanlon said, smiling. "I want you to live a long time and buy a lot of our products."
If he had to choose one piece of advice for artists, it would be to paint on a rigid support, rather than stretched canvas. Paintings yellow less over time when painted on a rigid support, and the paint film lasts longer.
Director's Blog, Natural Pigments website
"The Painter's Handbook," by Mark Gottsegen
"Traditional Oil Painting," by Virgil Elliott
The first article in this series, "To Make a Painting Last, Give it a Strong Foundation," about rigid supports for oil paintings, was posted last week. This is the second of two articles in the series.
Author's note: Thanks for Gage Academy of Art for awarding me a scholarship, which made it possible for me to attend the Painting Best Practices workshop.