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Optimus Primer: Choosing The Right Primer For Your Canvas (And Your Paints)

8 March 2016

Daniel Saez

Primer is the unsung hero of every great canvas painting, and indeed many of the masterpieces we now consider to represent the peak of canvas painting would have faded and disintegrated long ago without it. When applied to a canvas prior to painting, primer serves three main purposes:

• Longevity - Paint adheres to primer much more readily than it does to raw canvas, allowing a painting to resist peeling and cracking over time.
• Smoothing - The relatively rough texture of canvas is significantly smoothed by primer application, making brush strokes easier to apply and modify accurately. The level of smoothing achieved is based on personal preference, and glossy, mirror-smooth canvases can be achieved with enough applications (and patience).
• Protection - Some types of paint contain corrosive chemicals that damage canvas fibres over time, gradually causing a work to peel, crack and eventually disintegrate. Primer provides a layer of protection to prevent this occurring.

However, you can't just slap any old primer you find in the shed on your canvas and hope it sticks. For the best results you should always choose the right primer for the painting you are creating.

Oil primers

The choice of traditionalists the world over, oil primers have been used on canvas for centuries, and retain their popularity today for good reason. These primers are considered by many to be the only choice of primer for an oil-on-canvas painting, and the longevity of many famous oil-on-canvas paintings is testament to the durability of oil primer. However, despite this auspicious pedigree, oil primers can be just as useful to the casual or novice painter, as they are easy to apply and generally only require one or two coats to fully prime a canvas.

However, oil primer is far from a versatile choice, as it can only be used with oil paints. Furthermore, it cannot be used in isolation -- canvas destined for oil priming must first be sealed with a size such as rabbit skin glue or PVA, to prevent the oil in the primer provoking rot and fungal decay of the canvas. 

Acrylic primers

Acrylic primers are the best choice for artists who just want to get all the priming over and done with and start painting, as it dries in a matter of hours. You can also circumvent the need for sizing, as multiple coats of acrylic primer perform the same purpose as traditional sizing and do not corrode canvas fibres like oil primers do. Acrylic primers dry to a smooth, even surface suitable for both oil and acrylic paints, without the slight yellow tinge associated with some oil primers.

However, acrylic primers do not yet match the sheer durability and longevity of traditional oil primers, and you can expect a painting on acrylic primed canvas to be more vulnerable to cracking, peeling and other forms of degradation.

Gesso primers

Gesso is the jack of all trades of the primer world and can be used to prime canvases for oil, acrylic, tempera and even watercolour paints. The key to this versatility lies in its unique texture, which is achieved with the addition of gypsum, calcium carbonate or other fine, absorbent mineral powders. This texture creates exceptionally strong adhesion between paint and primer as well as providing effective protection for the canvas beneath. As such, gesso is prized by artists who prefer thick, textured surfaces and layers of paint.

However, despite gesso's versatility, you would still do well to match oil-based gesso to oil paints, acrylic gesso to acrylic paints and so on. If you mix different types of gesso and paint, the two layers will react differently to varying levels of heat and humidity, and the differing rates of expansion and contraction may start to de-laminate the canvas over time. Bear in mind that oil-based gesso will require an undercoat of size in the same way oil primers do.

For more information and options, check out your local art supplies store. 

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