Wednesday, 25 April 2012

How do I Prevent the Canvas on my Oil Painting Warping?

The last thing the artist needs is canvas warp occurring over time, particularly if the oil painting is large and ambitious. What can the artist do to prevent canvas from warping once the oil painting has been applied?

Problems with Stretching Canvas

Common culprits of canvas warp can easily be avoided with proper preparation of the art support prior to embarking the painting. (Read my article on what to do about canvas warp if it has already occured). Of course, the artist may purchase ready-stretched canvases from art shops. But if seeking a size not available or a particularly large canvas, the artist may wish to cut the cost of buying stretched canvas by preparing one’s own.

The image below serves as a guide on how to stretch canvas by rotation, beginning with point 1.

How to stretch canvas
Cheap Stretched Canvas by Stretching Your Own

If preparing a large painting, prefer thicker canvas to the thinner variety, as the ratio of thickness to dimensions will mean the canvas will be thin for its size. The finer weave may not withstand the extra pressures needed to stretch it over a large stretcher, causing the fabric to distort in places. A large canvas will also require crossbeams for extra support. If stretching your own canvas, follow these simplified steps.

How to Stretch Your Own Canvas

You will need the following art materials:
  • Good quality canvas purchased from a reputable art supplier such as Daler Rowney. If the painting is to be large (over 2.5ft x 2.5ft) use the thicker variety.
  • A rigid wooden stretcher on which to stretch your canvas. These can be purchased from art shops or you can make your own (see separate article).
  • A staple gun
  • Scissors
  • Hammer
  • Wooden wedges
  • Ruler and pencil
Trim the canvas material around the wooden stretcher, leaving at least 2 or 3 inches spare on each side.

Rest the canvas over a level worktop. You can place fabric or paper over the worktop to protect the surface of the canvas.

Rest the stretcher over the canvas. Determine central points of the width and length of the stretcher using the ruler and pencil.

Stretching Canvas Tips

Now bring one edge of the canvas over the edge of the stretcher and tuck it neatly over a centre-point of the stretcher’s length. Use the diagram as a guide.

Staple the canvas to the stretcher using the staple gun.

On the opposite edge, repeat this step. Pull firmly, not too hard or the canvas weave will distort at over-tensioned areas.

Staple this opposing edge onto the stretcher.

Work in rotation around the canvas as shown on the diagram, aiming to exert equal pressure over the entire canvas by basically 12 points. More staples can be added between these points to provide extra support.

For fine-tuning the canvas’ tension, gently hammer two or three of the wooden wedges into each corner of the frame between the canvas and the frame itself.

Stretching Canvas for Oil Painting

The stretcher itself should be rigid and lie flat when placed on an even surface. If mitre joints are not true, the canvas will not lie flat properly over the stretcher. For extra strength, you can add crossbeams over the back of the stretcher and use metal brackets instead of wooden ones for each mitre joint.

Causes of Canvas Warp

If the painting is stored in damp locations or where there are large temperature changes, this may cause the wooden frame to warp over time which can be transmitted to the canvas. As an extra precaution, apply a coat of acrylic primer over the wooden stretcher prior to stretching the canvas and use metal braces instead of wooden ones. Canvas paintings should be kept in a dry place.

What to Do About Canvas Warping

If however, the canvas has warped over time, the painting can be salvaged with care. I have written a separate article on repairing a warped oil painting.

Article on Oil Painting Materials

What to do about canvas warping
How to glue canvas onto panel

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