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ETH Canvas

Thank you for your interest.

Being a third-generation artist myself, I have grown up with and around people using and or making canvas and over the years, have made certain observations, essential to our craft.

Not formally trained, nor a self-proclaimed expert - herewith a few articles that I believe and hope will be helpful to artists, and interesting details that have made the world of difference to me in my humble journey.

- Bronwyn

Over the years I have been asked numerous times what the difference is between primer, gesso, size, ground and tooth ... and whether it is possible to paint directly onto an unprimed canvas.

Yes, it's definitely possible.... however, this leads to certain "challenges" including how the paint moves / behaves on your canvas as well as the chemical effect it will have on the cloth.

I've also had artists whose stretched canvases lose tension and become 'wobbly' after the application of PVA to their already primed canvas or where crossbars have actually snapped as a result of applying a water-based medium to the untreated, unprimed side of stretched cloth...

So, herewith my (broad) attempt to help make some sense of it all.

  • With acrylic paint - untreated canvas fibers may repel water, making "paint beads" and causing the paint not to flow

  • With oil paint - untreated canvas will soak up the oil resulting in crumbly paint, surrounded by halos of oil.

  • Weave could become more obvious than desired.

  • Discolouration (In the case of oil, yellowing, or in the case of acrylics, SID / substance induced discolouration - where impurities from the cloth are deposited into the paint through osmosis, resulting in a typically amber coloration)

  • Oxidation

  • Rotting (and subsequently smelling)

  • Delamination / Flaking / Cracking

  • Moisture in your medium can cause an unprimed, stretched canvas to shrink on drying which could in extreme cases result in your cross- / stretcher bars snapping!

  • Acrylic primer / PVA applied to a pre-primed stretched canvas, may result in a loss of tension and will need to be re-pulled before painting.

  • Primer, even the highest quality, has a limit. Turpentine is designed to corrode paint. Use too much and it will eat through any primer, dragging water / oil with it into the cloth.

(use ONLY the most refined, distilled artist's white spirit, like Gamsol to thin oil paint,

linseed oil and oil paint mediums which include petrolium distilates (like Liquin) Stay away from household turps!)


1. You can't paint with acrylic on an oil-primed canvas

Acrylics are basically plastic (polymers), so they are not breathable. As oils age, they release gases. If you paint with acrylics on top of oil, these gases will cause the acrylic paint layer to crack and flake off as the gases try to escape.

2. You can paint with oil on an acrylic ('universally') primed canvas

3. If you use an oil-based primer, you need to size (seal) the canvas first

4. If you use a high quality acrylic primer, no sizing is needed

Let's first look at a few terms:

"Support" / "Substrate" - surface you are working on (i.e. raw canvas)

"Ground" = layer onto which paint is applied - the part you experience with your brush

"Size" = Sealant

"Primer" = "Ground" = provides tooth

"Gesso" = traditional (old) term for primer

"PVA" = Polyvinyl Acetate (size / primer)

"Acrylic Dispersion Ground" = acrylic gesso / acrylic primer (fulfills roles of size, primer and ground all in one)

""Tooth" = texture of a primed canvas (coarse, medium or fine)


Raw canvas needs a waterproof layer between itself and oil paint so as to prevent it from sinking into the cloth and causing discolouration and rotting.

Size is a sealant / glue that reduces the absorption ability of canvas and which prevents water / oil coming into contact with the fibers of the cloth, which will over time, irrevocably damage it.

Size also stiffens the canvas and reduces the amount of paint you use (or that is absorbed by the cloth)

Traditionally, rabbit skin glue was used to size canvas, but this is actually hygroscopic, and continuously absorbs moisture from the atmosphere, resulting in swelling and shrinking and eventual cracking of oil paint (which is brittle once dry)


The quality of your ground directly affects your painting experience and handling, how smoothly it glides over the surface and how quickly your paint dries.

Your primer is what creates this surface.

GESSO (pronounced 'jesso')

Traditionally, gesso is a primer - used to create texture on a canvas, but not all primers are gessos, since modern acrylic primers also contain a proper sizing agent, which gesso doesn't.

'Genuine ('traditional or 'glue') Gesso' is the term used to refer to a mixture of hot animal glue and gypsum or chalk (and sometimes pigment.)

It is hard and chalky and comprises of many thin layers that is sensitive to water and will crack if used on a flexible surface like canvas! To prevent cracking and delamination (due to Zinc Oxide contained in many genuine gessos) therefore, only use gesso on rigid substrates. Being very absorbent, traditional gesso (it will be labelled as such) is suited for painting egg tempura or encaustic. Otherwise labelled "gessos" are made with an acrylic ground and are actually not absorbent enough for this type of painting.


Stay away from PVA's that are not specifically formulated for artists!

Look for Ph-neutral or acid free. Anything else will lead to deterioration and must be avoided!

It generally has high acidity, does not retain flexibility and has high colour change and doesn't tighten the canvas like high quality acrylic primers do.

PRIMER ('ground')

Priming is what gives your canvas texture / tooth, simultaneously stiffening and sealing the canvas.

Primer sticks better to your canvas than your medium would, essential to prevent your paint from flaking off once dry or delaminating when there is a sudden temperature change / the painting is removed from its stretcher or if it gets dropped / bumped, for example.

* PS - you don't need to prime unless you want the painting surface that priming gives - but then you have to size! You can paint directly onto modern size (not rabbit-skin glue!)



This is known as a "universal" / acrylic primer - fulfilling everything you need in one product.

It is water-based, and contains calcium carbonate (chalk), flexible acrylic polymer mediums (binder) / pigment (usually titanium white) and other chemicals to ensure flexibility, to ensure a long archival life.

It is not necessary to size a canvas before applying, since the acrylic polymers contained within the primer does this for you whilst providing the paint with something to properly stick to and provides a ground to paint on.

High quality acrylic primers are absorbent enough for your medium to physically merge with it, extending the longevity of your painting.


Oil primer is oil paint mixed with chalk to provide absorbency and tooth.

* You CANNOT paint with acrylic on an oil-primed ground

* Oil grounds can ONLY be applied over a size (otherwise the oil will be absorbed into the fibers of the cloth)

* Oil-primed canvases may appear yellow because of the linseed oil content

* Avoid lead oil-primers - these are dangerous and banned in some countries!

It is strongly recommended that you use oil / alkyd grounds on as rigid a support possible, to prevent cracking.


Colour is the refraction of light. Light bouncing off a flat ('toothless') surface is quite, simply 'flatter'. Based on the science of the gold ball, tooth on a canvas not only grips your paint, but increases the surface area off of which light bounces, thereby making your colours 'pop'.

To achieve tooth, you need a priming process, which includes the application of a number of layers of primer, sanded with a fine water-grit paper between layers, and re-pulled to optimal tautness before receiving medium. And boy, does ETH achieve it!

Our signature, water-based acrylic dispersion ground was especially formulated with the longevity of both acrylic and oil paintings in mind, providing the perfect texture / tooth whilst remaining beautifully smooth for detailed work.

It adheres beautifully to the canvas, and provides a surface to which both mediums can stick, whilst simultaneously protecting the cloth from water and oil. It has plenty pigment and higher opacity than average primers that are commercially available.

Our canvasses are expertly primed (and sized) resulting in a texture that is perfect for any medium. In addition, our particular choice (weight and weave) of cotton duck contributes to the efficacy of this process: Tighter threads, woven in a stronger pattern. It’s quite simply a winning combination!


In summary - knowing the 'science' behind how your canvas responds to certain treatments will stand you in excellent stead to get the most out of your canvas, and a work that will last much longer than it otherwise would.

We offer white, clear and colour primed canvas.

If you are serious about your art, you need to choose the highest quality.

Your sanity (and reputation!) depends on it.

Choose ETH.

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/ˈkanvəs /

Der. 13th century Anglo-French “canevaz” & old French “canevas”, der. Vulgar Latin “cannapaceus”

Or “made of hemp”, der. Greek : κάνναβις




  1. 1.

a waterbird with a broad blunt bill, short legs, webbed feet, and a waddling gait……..

D-U-C-K….. (not D-U-C-T !) simply comes from the Dutch word “doek”, meaning “cloth”.

Canvas comes in two forms: plain and "duck".

Duck is a heavy-duty cotton fabric, sturdier than plain cotton and holds shape better than standard canvas.

Both duck and plain canvas are standard (plain)-woven fabrics, but there are a few differences between them:

Duck is more tightly woven than plain canvas.

  • Duck is graded on a scale of 1 to 12, with 12 being the lightest fabric and 1 being the heaviest. (Classification system, established in the 1920s.)

  • Duck is made exclusively from cotton, hence sometimes referred to as cotton duck canvas or cotton duck fabric.

By definition, there are two types of "canvas"

Linen is produced from flax plant fibers (and substantially more expensive since it is harvested by hand in Europe.

Cotton canvas is produced from the white “candy floss” bit, found around the seeds of cotton plants (and more affordable, since it is commercially harvested)

Cotton 'Duck' only really became popular round about the 1850’s, with the advent of acrylic paint, however one of the earliest surviving oil paintings on duck canvas was one discovered in 1410, Madonna with Angels, in Berlin.

Under the Cotton category, you get 'plain' and 'duck' cotton …..which is how we arrive at the term “Cotton Duck”, the cloth we use to manufacture our signature brand canvas.

The reason that we use the “Duck” and not the “Plain” variation is that Duck threads are a lot more tightly woven, which is very important. Looser threads pose the risk of over-stretching or even tearing when stretching onto a frame. In addition, the tighter your weave, the better and more consistent the application of your primer.

Duck is flexible – and it’s strong.

In weaving a canvas, the plain vs. the twisp weave is used since it is the strongest and most hardwearing of the weaves.

Cotton duck, uses a variation of this plain weave, called the “basket weave” – where two or more threads are bundled and woven (vs. the “one-up-and-one-over” or “balanced plain weave” variation), again for added strength and durability, and ultimately to facilitate the sizing, priming and sanding processes we apply to arrive at our finished product.

We use a 340gsm grammage in our signature brand.

This is where I have to mention how especially vital it is that the cloth is stretched properly, especially for larger paintings. At ETH Canvas, our years of expertise in this field have enabled us to supply you not only with professional advice in this regard, but bespoke customization where required.

Close attention is paid to the construction of our stretchers and the technique employed to stretch the cloth. Every tiny detail counts - right down to the tools that we use - our stretching pliers being especially imported from Germany since we have found that locally supplied pliers not only tend to damage the canvas , they are just simply not strong enough for the techniques we employ.

Without getting too technical, a canvas needs to be “sized” (especially cotton) before priming.

This is the process by which a layer of gelatinous material is applied to the raw canvas prior to priming, so as to seal the pores in the surface of the cloth. This ”waterproofing” is vital in preventing fluid (paint) from seeping through into the fibers of the canvas and ultimately rotting the cloth. It also obviously reduces the volume of paint you need.

The primer we use does both. Our canvasses are expertly primed (and sized) resulting in a texture that is perfect for any medium. In addition, and to bring you back to point, our particular choice (weight and weave) of cotton duck contributes to the efficacy of this process: Tighter threads, woven in a stronger pattern. It’s quite simply a winning combination!

By no means disregard the natural beauty and smooth, stiff painting surface provided by linen, the qualities that originally seduced our masters of old … but when it comes to canvas - the quality that is an ETH Canvas remains unparalleled.

Give your work the gift of immortality with an ETH Canvas as it transports you through the realms of your creative process. Perfectly smooth, non-absorbent and expertly stretched, with just enough tooth to ensure maximum reflection of colour and light.

We guarantee it. We are artists ourselves. We know exactly what you need in a canvas.

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"Why would you choose a canvas with wedges ? Surely if it is stretched properly, they're unnecessary?"

This is true, to a degree. Ultimately, whether to choose wedges or not depends on a number of factors, including the dimensions of your canvas; its profile (depth),; your medium and painting style; whether the finished work is due to be transported at any stage; handling, geographical location with respect to environmental & temperature changes (sunlight, cold and humidity can all affect the fibers of your canvas) and, as it becomes heavier during the painting process, the cloth may move and loosen, regardless of how perfectly it was originally stretched.

But that's not all that properly made, installed and functioning wedges are good for ... another fantastic benefit is that a wedged stretched can be dis- and re-assembled. This is especially handy for art that is exported in a tube - and largely facilitates the re-stretching process once your work reaches its destination (especially given that decent stretching facilities are often either lacking, sub-par or extremely expensive abroad)

Wedges, "spacers", "chocs" or "keys" are adjustable “wedges” of wood that are fitted into the corners of canvas stretchers. These are used for “re-tightening” your canvas should it have become loose or ‘bouncy’ over time, during transit, as a result of environmental fluctuations or simply because of pressure applied to it during the painting process.

Most pre-made, cheaper canvases have “slots” cut into them (where wooden or even plastic wedges are supposed to go) and the wedges themselves supplied separately, often loose within the canvas packaging... leaving you with the often impossible job of fitting them into their ‘designated spaces’ before being able to tap them in.

We do things differently at ETH. We used a unique dovetail system which provides for the wedges to be pre-fitted at all the necessary points (8 wedges installed in each corner, and 2 wedges installed per cross bar). No glue is used in the wedge-system, and only a single "stabilizer" staple which is designed to pop out when the wedges is tapped in. This alleviates some of the stress of ensuring that the tightened canvas has equal tension all round and that they don’t splinter or crack the corners of the frame when you are tapping them in (a common complaint I hear time and again). In addition, we use only kiln-dried obeche timber (so most of the moisture has been removed) which is knot- free eliminating the natural tendency of cheaper "knotted" timber stretchers to split - usually at the moment you try and whack in a wedge.

Each set of our wedges are individually cut during the manufacture of each stretcher and I can promise you - they work like a wedge is supposed to! ETH Canvas is one of few (if not only) local supplier that are able to manufacture box (deeper edge) frames with a wedge system – right up to a profile of 50mm. In addition, and unlike other systems, there is little to no chance of damaging the canvas when you hammer the chocs in, since they are designed as a complimentary functioning set and sanded to ensure they don't damage your cloth. Another anomaly of pre-made, mass-produced chocs supplied with cheaper canvases.

A nicely tightened canvas vibrates like a drum membrane if you flick the center of it with your fingers. The less vibration, the more tightening that is required.

How to use a wedge-system to re-tighten a stretched canvas

If your canvas is unprimed, do NOT use the wedges until priming is complete - the priming process itself causes contraction of the cloth, rendering the canvas tauter on the stretcher.

For smaller canvases and using a rubber hammer, gently tap the end of both wedges into each corner, working your way around to each corner. As you tap the wedge, the space at the corner of the stretcher may increase. Don't be alarmed. This means its working.

It is advisable to check the progress of your tightening after each wedge position and that you stop once the canvas is taut enough – once the wedge is embedded, it cannot be removed and if you "over-tighten", it can create too much pressure within the stretcher structure and end up warping your frame.

NB - For larger canvasses, you need to expand the facing stretcher bars first, to keep the tension on the canvas even. So, tap the wedges that push one of the stretcher bars in one direction, then rotate the canvas and do the same for the wedges pushing the opposite bar, in the opposite direction. Then, repeat for the other sides.

It is never a good idea to tap too hard, for obvious reasons, since you always run the risk of overcorrection or the wood splitting – tap means “tap” (not bludgeon...). Please be wary of this, and rather tighten and rotate a second time, to be on the safe side.

How to extend the longevity of your painting.

Keywords are: COOL and DRY


- Direct sunlight or sudden or extreme changes in temperature

- Leaning panels and stretchers against walls and directly on the floor (use blocks to raise them)

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