Sunday, June 12, 2016

Preping a canvas for oil painting, ultimate contemporary guide

The age old question.. how did the masters prepare their oil painting ground? "Their paintings have lasted thru the centuries and mine wont even last till the end of the semester" is what I used to think in art school.

So why is a preparing a canvas for oil painting the key to a paintings longevity?

Fabric used for oil painting supports is usually cotton canvas or linen. (In this post I will talk about cotton canvas, as linen canvas is rarely used and needs its own post)

With time the oil from the oil paint rots and weakens the canvas so there needs to be a barrier between the raw canvas and the oil paint. This barrier is the sizing and painting ground.

Sizing:
Sizing prepares the raw canvas for the painting ground. It reals in the raw canvas fibers and prevents moisture and oil absorption. In the old days master painters used rabbit skin glue as a natural sizing. Its still available, Utrecht art supplies sells it. It is sold dry and has to be cooked to use. 
Utrecht Rabbit Skin glue, buy here

Gamblin Rabbit Skin glue, buy here

 I know many artists swear by rabbit skin glue but its not my favorite. When cooking it, it has a tendency to get lumpy and smells.

Also, it expands with moisture. To me it seems a little outdated. I'm sure if DaVinci was prepping a canvas now, he wouldn't mess around with animal glues and use a more innovative method of acrylic sizing.
Acrylic sizing really seeps into the fibers of the canvas and seals it and as of right now it is my choice of sizing. (I am still testing different animal glue sizes, a Williamsburg one, so we will see how it works)


My sizing of choice:
Acrylic PVA glue sizing

Utrecht sizing, buy here     or       Gamblin PVA sizing, buy here

 
Gesso:
Gesso painting primer can be either acrylic or oil.

Acrylic gesso and why I don't use it:
It seems that acrylic gesso is the most popular gesso for painting. While its great for acrylic paint its not suitable for oil painting.
All thru art school and continuing education I used acrylic gesso. All teachers recommend it and its a doable primer. But as I perfected my skill I noticed that no matter how I prepared by canvases and how I painted I was still getting matte area on my painting, where the oil seep into who-knows-where(cause it was not showing on the back of the canvas)
So I did some research and found that it was the acrylic gesso that was causing these matte areas. The canvas was not sufficiently sealed and needed an oil ground to prevent this.
Now I use oil ground and wow what a difference!

Oil ground: (best primer for oil painting)

Oil ground has made the biggest difference it the quality of my paintings. The color saturation is much better, they have a buttery feel and the luster of the paint is consistent with no more matte areas. When using this primer the colors applied on top have luminosity and depth. Oil painting ground has the same texture are oil paint. Whereas an acrylic gesso is matte, dry and chalky looking. This causes the oil paint to loose its buttery texture and look plastic-like.

I use the Utrecht oil ground. It does have Lead pigment in it so I am extra careful and use cloves. Also it is best to have good ventilation as it does have a turpentine-ish smell.
Applied in 2 coats(let first coat dry to the touch before applying the second one). It has a longer drying time, once the second coat is applied wait 7 days before painting.

Utrecht oil ground, buy here 

Gamblin also makes an oil ground BUT it is alkyd resin based. I don't use this one cause I stay away from alkyd resins.


So that is the secret. To prime a canvas for painting with sizing and oil primer.

Canvas priming break-down:

1. Stretch the canvas and make sure it is tight, but not too tight as that can cause warping. (I'll write a separate post about canvas stretching) Also I sometimes iron the canvas prior to stretching, as it is IMPOSSIBLE to get rid of creases after sizing.

2. Apply the sizing evenly. I use two coats which I let dry in between application. Then let dry for 48 hours. I prefer to let the sizing dry for 3 days as oil painting and primer are so sensitive to moisture. Its best to give it extra time to evaporate just to be safe.

3. Once the sizing has dried I apply the oil painting ground. Its a little messy so first I use a palette knife to scoop it onto the canvas and then spread it with the knife. Let it dry for 7 days then re-apply the final coat and let that dry 7 more days. I know this is time consuming but the result is worth it. Master painters prepared painting grounds for months (most had workshops for ground preparation) often times sanding the ground up to 4 times.

Safety point: I do not sand the ground. This is an important part as the painting ground has Lead pigment it in. Its not dangerous when working in gloves but when sanded the particles can get into the lungs. That is why I take time to apply the ground evenly the first time.


Conclusion:

Repairing a canvas with oil ground is time consuming but so worth it. When first learning to oil paint you will make a lot of work and it is fine to start with acrylic gesso but try to upgrade to oil ground. It completely changes the paint surface and is so rich and buttery to paint on. It makes the colors rich and bright without developing matte spots. Also it is most archival and will last for years. If you are gonna do something, might as well do it right.



















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