How To Stretch A Painting On Canvas Using Picture Framers Stretcher Bars


Stretching a painting on canvas is quite easy when you follow some simple steps. When a painting has been done on cheap canvas or some other poor material it is best to seek professional picture framing advice because stretching some pictures is challenging and awkward. In this article you will learn about how to stretch a canvas painting, how to choose and cut a stretcher frame and how to finish off the stretched painting so that you can hang it for display.

Artists have chosen various surfaces for painting on over the centuries ranging from raw plaster walls, wooden panels, paper and fabrics. When an artist paints on fabrics it is usual to prepare the canvas first with a primer. The priming layers are very important when it comes to providing not only the right surface for accepting paint but also to provide a long-lasting support that will not deteriorate easily.

As a quick overview to help you understand the nature of a painting on canvas the steps taken to prepare a traditional canvas are as follows.

The first step was to choose a suitable fabric. Artists preferred to use linen over other fabrics due to its strong fiberous construction and stability. Cotton canvas was a poor second choice when linen was unavailable. the fabric was traditionally coated with a sizing coat made from animal glue or pearl glue. These glues are made from gelatinous materials extracted from rabbit skins and other animal products. The aim of the sizing was to coat each and every strand of the fabric with a layer that when dry would seal and protect the fabric.

Picture-Framers-Stretcher-BarsThe second step was to make a mixture from rabbit skin glue mixed with dead plaster and whiting or chalk. Dead plaster is made by stirring plaster of Paris with water for about half an hour. When you mix plaster beyond its setting time you change the crystalline structure preventing it from drying out and setting like traditional plaster, hence dead plaster. The dead plaster has a different structure than the whiting that is added to the glue to make the artist’s gesso.

The warmed mixture of glue, whiting and dead plaster was then applied to the surface of the pre-sized fabric. Several coats are applied in successive and alternate layers building up a smooth toothy surface that will accept paint. The trick to applying the gesso was to apply a layer and then wait for it to lose its glossy appearance before you applied the next layer. After several layers the canvas was set aside to dry.

Artists would often do this preparation to the fabric after it had been stretched over a supporting frame.

The fabric had first been stretched over a tapered bar called a stretcher bar.

It is important when stretching paintings that you choose a suitable stretcher bar that either has a rounded raised lip or a tapered bevelled profile.

If you just use a flat piece of timber for your stretcher frame you will create problems in the painting later by causing an impression line where the timber touches the back of the picture.

Picture-Framers-Stretcher-BarsModern artists often buy pre-primed artist canvas and linen that has a synthetic gesso coating on its surface. It is even acceptable from a conservation standpoint to use synthetic polyester fabrics rather than linen or canvas. These synthetics are more stable and durable than some of the organic fabrics.

One big problem is with developing countries where artists are unable to obtain quality supports. I often encounter paintings that have been done on cotton bed sheets, hessian bags and tarpaulins. These each present different challenges when trying to make them presentable.

Basically to stretch a canvas that has already been painted on it is necessary to determine whether the fixtures or staples you will use will go on the side or the back of the stretcher first.

The process of stretching a canvas involves either cutting and joining some lengths of stretcher bars into a frame or buying pre-cut slotted stretcher pieces from an art store.

The slotted corners are made with a sliding tenon joint that allows you to tension the canvas further after stretching over the bars. There are several methods of achieving adjustable corners to allow further tension to be applied to the canvas by expanding the corners..

NOTE: If you use a slotted variety of stretcher bar ensure you have it squared up before you stretch your canvas otherwise the painting will be crooked. Measure the diagonals to check squareness.If the frame is a parallel and the diagonal equal then it is square.