Canvas, Stretching & Care at the VanArtHub gallery in Vancouver

Canvas and stretching

The bars under the painting decide how long it lasts

Stretcher bars, how a canvas is mounted on them, why one goes slack, and what Vancouver damp does to a painting on fabric. The hub behind our canvas stretching service.

A canvas is a piece of fabric held under tension, and tension does not hold itself

Almost everything that goes wrong with a painting on canvas starts underneath it. The fabric is stretched over a wooden frame and held at a tension the artist chose, and from that day onward the timber and the fabric both respond to the air in the room. Wood takes up moisture and lets it go. Cotton and linen do the same, faster, and they move further.

That is why a canvas that looked taut for fifteen years can suddenly read soft in the middle, and why a painting shipped rolled in a tube cannot simply be tacked back onto any four lengths of pine. This hub covers what the bars are, how a canvas goes onto them, why it slackens, and what a wet climate does to the whole assembly.

cross-brace keys bar depth mitred corner, deliberately not glued
A stretcher seen from the back. The bars are mitred at the corners and left slightly loose on purpose, because the eight wedges, called keys, are what let the frame be pushed very slightly wider later to take up slack. A bar longer than about 100 cm bows inward under the pull of the fabric, so it gets a cross-brace.

The four woods we use most

  • Oak Open grain, warm and pale. Lifts landscape and anything with a lot of light in it.
  • Ash Paler and calmer than oak. The safest choice against a white wall.
  • Maple Fine, almost closed grain. Reads as clean rather than rustic.
  • Walnut Dark, close grain, slightly purple in daylight. Weight without going to black.

Colour and relative width only. These are drawn, not photographed, so they share one light source and can be compared against each other. Real grain varies piece to piece, and we will show you the actual moulding before anything is cut.

Every guide in this hub

Canvas, Stretching & Care

The process

Materials

Care & repair

Buying

Common questions

Questions about canvas and stretching

What is the difference between stretching and re-stretching?

Stretching puts a loose or rolled canvas onto bars for the first time. Re-stretching takes a painting that is already mounted, lifts it off, and mounts it again at the right tension, usually because the fabric has gone slack or the original bars are too shallow or have warped. Re-stretching is the more delicate of the two, because the paint layer has already dried in one position.

My canvas has gone soft in the middle. Is that serious?

Usually not, and it is very common. Canvas relaxes over decades and reacts to humidity within days. Most cases are solved by tapping the keys, the small wooden wedges in the inside corners, which pushes the bars apart slightly and takes the slack up. Severe slackness needs a full re-stretch. See why a canvas goes slack.

A painting arrived rolled in a tube. What do I do with it?

Leave it rolled until it has come up to room temperature, which usually takes a few hours, then unroll it flat and let it relax before anything else happens. Unrolling cold paint is how paintings crack. Bring it in rolled and we will stretch it. See stretching a rolled canvas.

What depth of stretcher bar should a painting have?

It depends on the size and on whether it will be framed. A small piece is fine on a shallow bar. A large one needs depth and often a cross-brace, because a long bar will bow inward under the tension of the fabric. A gallery wrap that hangs with no frame usually wants a deeper bar so the edge reads as deliberate. See stretcher bars explained.

Does the damp here actually affect a canvas?

Yes, and it is the single most underrated thing about owning a painting on fabric in this city. Months of high humidity followed by dry indoor heat move both the timber and the fabric, repeatedly, in opposite directions. It shows up as slackness, and over a long enough period as cracking. See canvas, damp and humidity.

Do you stretch canvases people bring in?

Yes. Rolled canvases, loose canvases, and paintings that need taking off tired bars and re-mounting. Bring it to the gallery on Davie Street and we will look at it with you. See canvas stretching in Vancouver.

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Rather just ask someone who does this every day?

We frame original paintings in-house, at our gallery on Davie Street. Send the measurements and a photograph and we will tell you what the piece needs, including when the answer is that it needs nothing.

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