What is gesso?
Gesso, pronounced ‘jesso‘, was traditionally used to prepare or prime a surface so Oil paint would adhere to it.
Gesso is the same as a primer, as in ‘pre-primed canvas’.
It is made from a combination of paint pigment, chalk and binder.
Traditional Oil ‘glue gesso’ was made with an animal glue binder, usually rabbit-skin glue, chalk, and white pigment, usually Titanium white.
Gesso is usually white or off white and is used after you have sealed the raw canvas with a coat of size (see: the Trouble with Oil)
It creates a surface that is both absorbent (particularly useful for ‘dead’ colouring with oils) and has a ‘tooth’ (texture) that allows paint to grab onto the surface…
So what is Acrylic Gesso?
Modern acrylic gesso is a combination of calcium carbonate (chalk) with an acrylic polymer medium (binder), a pigment (titanium white) and other chemicals that ensure flexibility, and ensure long archival life.
Why do I need to use a gesso primer for Acrylic painting?
Technically you don’t. But in practice painting directly onto a raw canvas is not an enjoyable experience. Unless you are interested in deep staining effects like Morris Louis who became fascinated with using diluted acrylic paint to stain the raw canvas, rather than apply with a brush.
Morris Louis (American, 1912–1962)
Acrylic on canvas
Can I use acrylic gesso under an oil painting?
Yes and no.
Yes for 90% of your paintings especially if your just beginning ‘acrylic gesso‘ will be fine if the raw canvas has been properly sized, thus protecting the canvas from the corrosive nature of oil.
However, if it was for a portrait or to produce a masterpiece for your painting legacy I would use an Oil gesso purely for the fact it has been time tested and the Oil will always adhere better to Oil than sitting on top of an Acrylic.
Pro tip: If you want the first layer of paint to dry quicker than it normally might, just add gesso. The gesso primer layer can soak up the oil from within the paint and leave a ‘dead’ flat under painting that won’t have any sheen to it. Imagine the difference between painting onto glass and painting onto blotting paper. All the oil from the paint would be absorbed into the primer layer.
Do I need to buy it?
Homemade or ready made?
Shop bought gesso comes pre-prepared in tubs or tubes and is pretty good, homemade gesso is cheaper to produce and can be adjusted to personal needs and tastes, however, it’s not needed when you are first starting painting.
Artist or Student quality?
As with paints, the difference between the two is dependent on price. The artist quality having a higher price, more pigment and a higher opacity. The student quality will have a lower quantity of pigment and more filler. If you are painting onto a raw canvas the artist quality would be best due to the increased opacity. For adding a bit more absorbency to a pre-primed canvas student quality would be fine (you can always add a bit more white pigment to it).
Can I colour the gesso?
Yes, I am a big fan of working on a coloured ground and if you are pushed for time you can mix some paint into the gesso to tint it. You can also buy premixed black gesso, coloured gesso and clear gesso.
Pre-primed canvas boards
“Pre-primed” means “pre-gesso” It already has a gesso layer applied in the factory. On the cheaper ranges for some reason manufacturers often use a seal on top which creates a shiny surface which is completely ridiculous… defeating the object of gesso!
If you are using watered down paint or student quality paints the shiny surface can repel the paint. The more watery the paint the easily it will sit on the surface and not soak into the canvas as you would like.
If you apply a couple of coats of gesso it will form a more absorbent surface due to the chalk (calcium carbonate- known as ‘whiting’ in oil painting) found in the gesso.
Creating a super smooth finish
You can sand gesso between coats to create a lovely smooth finish, especially handy for photo-realistic paintings, just sand each layer with a fine sandpaper. Say a 240 grit. 3M’s make a good sandpaper. Just make sure you do it outside, or in a well ventilated area as it goes everywhere!
How to gesso a raw canvas for acrylic painting
What You Need:
- Decorators brush
- Kitchen Roll
- 240 grit sandpaper if you want to sand the layers in between each other.
- Buy a tub of premixed white gesso and give it a stir. Again, this really comes down to personal preference, I work from a tub so I can control the amount of gesso on my brush for each stroke but you can buy it in tubes.
- The first coat always needs to be diluted with a touch of water (sometimes people recommend adding a bit of acrylic medium to prevent cracking but the layer is so thin and soaks straight in, it would never crack).
- Allow to dry, then apply a second coat. This can be applied thinly and does not be watered down. If you want a more absorbent surface, add another layer.
- When applying the gesso turn the canvas 90 degrees between coats to insure an even coverage.
- Apply a final coat using the pure, undiluted gesso.
- Using a 3 inch decorators brush, apply the gesso directly to the stretched canvas in even strokes. Work from the top to the bottom of the canvas, in parallel strokes from one edge to the other.
- Wash your brush out immediately in running water then use a brush cleaner to thoroughly remove the gesso out. It’s worth cleaning it twice even if you think it’s clean.
Pro tip: Golden paints make a hard gesso that can be useful if you are working on a board. Due to the limited movement on a board compared with a canvas it can create a smoother finish.
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