Wednesday, 15 September 2010

Why is My Oil Painting Cracking?

Weeks after completing an oil painting, hair cracks begin to form on the paint layer. The dry paint may begin to flake off or become powdery to the touch. The upper layers seem to become brittle and dull. The reason for a cracking oil painting can go back to improper preparation.

Why Cracks Appear in Oil Paint


Reasons for a Cracking Oil Painting
Rachel Shirley
I believe oils are the most robust and durable of all art mediums and little attention is required. But a cracking oil painting is a problem the artist most fears. The cause of cracking often goes back to poor practices in oil painting and associated materials. How can the artist prevent cracks appearing in an oil painting?

Oil Painting Do’s and Don’ts

Investing a lot of time in an oil painting deserves the best art materials, or the time will be wasted. The following advice will help prevent the frustration of a cracking oil painting.

As with anything, never use a substitute product for the one that is designed for oil painting. For instance, avoid using household emulsions or cheap primers to prepare the painting support. Some of these may not provide a sufficient barrier against the absorbent properties of the canvas or board. The result of this is that the still-absorbent support will suck the oil vehicle from the paint, causing it to brittle, and cracking may result. Stick to a recommended oil painting primer, such as Winsor & Newton or Daler Rowney, although a good quality acrylic primer is fine for oil sketches or quick studies.

Do not use mediums and solvents designed for household or industrial use in place of those specifically designed for oil painting. They can affect the permanence of the pigments. Turps, paint strippers and household varnishes will also ruin art brushes and emit powerful odours. Stick to artist’s agents such as Sansador or artist oil painting varnishes.

Never combine mediums with varying drying rates, such as stand oil (which dries slowly) with alkyd mediums (which dry quickly) in the same painting. This will cause stresses in the painting layer as it dries and inevitable cracking. Stick to the same medium in any one painting.

What is the Fat Over Lean Rule?

When working in layers such as when glazing with oil colours, introduce a little more oil medium into your oil paints. This practice merely entails mixing a little oil with the pigment before applying it to the painting. Known as “fat over lean” or “flexible or inflexible,” this practice provides flexibility to the upper layers of paint and will prevent it from cracking.

Linseed oil is most commonly used for fat over lean, but other oils are suitable, such as stand oil, safflower oil or oil of spike lavender. However, it is best to stick to the same oil medium for each painting as this will prevent conflicting drying rates in the paint.

Proper Use Of Oil Painting Products

Always read the manufacturers’ instructions properly, as some art products might require special preparations. Items such as rabbit skin glue or oil primers often need to be used in a specific way.

Never varnish an oil painting until it is thoroughly dry. Oil paint that is not quite dry could adhere to the varnish layer and cause it to “move” with the varnish as it dries and contracts, causing the oil paint to crack. Further problems may present themselves in the future when it comes to removing the varnish for cleaning, as some of the oil paint may come off with it the varnish.

Art Materials to Prevent Cracking in Oil Paint

Winsor & Newton Refined Linseed Oil 75ml
Linseed oil
click to buy from Amazon
It is essential to use proper artist products for oil painting rather than those designed for industrial use. Linseed oil, Sansador, Stand oil or Turpenoid are suitable for thinning the paint and cleaning the brushes. Similarly using proper artist primer for sizing will prevent the absorbent painting support form sucking the oil from the oil paint. Artist’s gesso or acrylic polymer primer is most often used.

Any oily art medium can be used for the fat over lean rule to prevent the upper glazes of oil paint from cracking but linseed oil is most often applied. Artist varnishes are available for any finish from matt to gloss, so long as the oil paint is thoroughly dry (after six months or so). With this in mind, oil paint is a very forgiving medium, and few artists have encountered cracking in their oil painting, even with short cuts.

Links Relating to Oil Painting Practices

6 comments:

Anonymous said...

Besides linseed oil a newer, but similar medium is soy esters which blend quick and have great flexibility that avoids cracking. This can be found on line from Natural Earth Paints and SOYThin through MacPherson's Art Supply.��

Colleen said...

I have painting that are 125 to 150 years of age. I don't want them to peel or the paint to crack. Is linseed oil the best source?
I had someone tell me to put it lightly on the back of the canvas. I also have a couple on wood.my e mail is ctedgell@ yahoo.com

Rachel said...

Hello thanks for Q
You say you have paintings that are 125 to 150 years old. Have you thought of having them valued? They might be worth insuring or looking into. If there are no cracks in the paint layer, I would discourage preventative measures, with the view that if it is not broken, don’t fix it. Simply keep the paintings in a dry, cool place out of sunlight.

If you do see signs of cracking, I would recommend a professional restorer. Oiling out a very old oil painting is unlikely to cure cracking, as it is like trying to moisturise old skin. The wrinkles will remain and so will the cracks.

Also worth bearing in mind that the cracks might not be the paint layer itself, but the varnish. Some varnishes, such as Dammar creates a hard, inflexible layer that cannot tolerate temperature variations, which sets up stresses over the varnish. The paint, adhering to the varnish is likely to shift with the varnish.

Having said this, oil paintings are extremely robust and this problem seldom occurs.

A professional restorer would be able to establish the cause of the cracking. Removing the varnish would be the answer. But take care that the paint does not come off with the varnish. Again, I would strongly recommend going to a professional restorer for oil paintings that are old and possibly valuable.

Good luck!

NYCMuseumSketch said...

Oil of spike lavender is not an oil - it's a solvent. It's an alternative to turpentine for dissolving damar varnish in your medium, and it also makes you medium smell nice. http://www.jerrysartarama.com/lavender-spike-oil-essence

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Donna W. said...

I have been holding a painting for a client and will be delivering it mid-December. About a month ago, I noticed one small area (solid black part of a silhouette) that had begun to crackle. I mixed a bit of color with a good amount of linseed oil (I am working with water mixable oils and mediums), and glazed over the area. It seemed to fix the area, but after 2 weeks it began to crackle again. I repeated the touch up process making sure to use plenty of medium, but again, after about 2 weeks, it is crackling, and the area is very dull. What do you recommend?