Practical | The Importance of Surface Preparation with Dr. Paynt

Dr. Paynt was a regular contributor to Art All magazine, providing practical tips and advice for artists. In this edition he takes a look at What Lies Beneath and the importance of preparing your surface. We also keep an archive of Dr. Paynt’s columns over on for our members. 

I cannot stress the importance of surface preparation enough – everything is built from the base up, and if the ground is not prepared to your needs then it will be more of a struggle to achieve the desired result. Besides, good preparation is the cheapest and most effective way to ensure a good outcome. Instead of being a hurdle before you can get painting, preparation of the surface is a stress-free way to start your dialogue with the work – what could be easier than prepping a canvas, painting white on white?

Priming a surface seals it, reduces the absorbability, fills the weave of fabrics, gives a purchase for the paint film, and acts as a reflector to bounce light back through the paint layers.

For some techniques, such as drawing or watercolour, attending to the surface may be as straightforward as choosing paper, although here it pays to be particular too. If you want to erase a lot or work the paper you will need a durable paper. If you want to reproduce the work, a bright white paper may suit better. Every type of paper will behave differently and be more or less suited to what you want to achieve.

Priming a surface is optional if you’re using acrylic, as they will go on virtually any grease-free surface. You can paint acrylic on a heavy paper (300gsm+) and get a different effect if you prime the paper first – unprimed, the paint will take quicker and the result will be less blended and the colour slightly darker.

Priming is necessary for oil painting, except on special oil painting paper, as the oils will damage unprotected fibres.

Pre-primed canvas can be painted on straight away, but factory-primed surfaces are usually thin and not sufficient to properly fill the weave. They just want to seal the canvas and get it out the door as quickly as possible – time is money! You will improve the surface hugely by applying two or more further coats of primer. By applying additional coats of primer, the initial paint film glides on without leaving “holes” where the primer shows through. Colour intensity is heightened by having the substrate white as possible, to reflect light back through the paint layers – the brighter the ground, the brighter the paint films will appear.

For acrylic painting, acrylic gesso is the best primer, being a similar composition to the paint and providing an ideal tooth for it to bond to. Nearly every paint manufacturer produces an acrylic gesso, each with its own characteristics. Golden Colours from the USA make several primers for acrylic, including an absorbent version for using with very dilute acrylics, a hard sandable gesso for super smooth surfaces on rigid supports, and a black gesso. Gesso is applied in a thin, dilute first coat, then in heavier layers with a flat brush. It is not ideal for building up heavy texture, as it can crack if applied to thickly (modelling pastes are better for this) but random brush strokes can create an interesting play of light, or you can sand between coats for a smooth surface.

Acrylic gesso can be used for oil and alkyd colours, but is not ideal, due to the expansion rates of acrylic and oil being different. The best primers for oil are more absorbent, so the oilcolour bonds properly to the surface. True handmade gesso (made using hide glue, whiting, and titanium white) is a superb ground for oilcolour, but should be used only on rigid supports, such as board, as hide glues are more greatly affected by moisture than canvas, so can cause cracking. For flexible supports such as canvas, German producer Schmincke produces a similar product called “Absorbent Primer”, which is a flexible half-chalk primer that gives the same plaster-smooth finish. Traditional oil painters may want to use an oil-based primer for the particular bond and look it provides – Winsor & Newton produce a very good alkyd-based Oil Primer.

There are specialist primers expanding the look of traditional media and allow watercolour, gouache, silverpoint and pastel to be effectively painted on canvas. New types of primers that integrate digital printing with painting are available too. Anything is possible if the ground is properly prepared!

Primers are usually brushed on, using a flat bristle brush. The da Vinci 2410 Brush is a traditional gesso brush made from 4-fold thickness hog bristles so it holds a lot of primer and lays it on nice and even. Primer can also be applied using a paint roller. Sanding between layers is optional, though it pays to give pre-primed canvas a good sand to cut any surface grease and give a good key for the primer. Sanding gesso is best done with 320 grit sandpaper, with 600 grit sandpaper giving a good finished polishing to the final layer.

Two warnings: Don’t use house paint or house paint undercoat to prepare your artwork – there is a reason they recommend re-painting your house every ten years. Also, by the time you’ve prepared your beautiful surface, you may not want to spoil it with paint!