Stretcher vs Strainer
In the 16th century, artists found it better to use fabric stretched. It allowed them to have a better mode of transport, a larger size for the artists needed a wooden frame. Strainers and stretchers are the auxiliary support of painting paint on canvas. They are used in other techniques: paper, bark painting and some process of conservation too.
The terms strainer and stretcher refer to the frame (more common is a timber frame) around the canvas that is stretched to give a flat surface to work on. It can be reinforced by adding one or more pieces of timber to the wooden frame.
The difference between strainers & stretchers
Strainer
The strainer is a frame where all the corners are fixed, they can be stapled, glued, nailed… Strainers are really common to be used by artists as less expensive than stretchers.
Stretcher
At the beginning of the utilisation of canvas on the wooden frame, artists were mainly using strainers. With time, the canvas comes loose and is required to be restretched on a slightly larger strainer. Repeat this action damages the edges of the painting. For this purpose, the adjustable corners have been created.
Therefore, the stretcher is a frame where the corners are mobile, allowing adjustment of tension. It is possible by the presence of wedges (sometimes called keys), and small wooden (or plastic) triangles fitting in the join inside the corner.
They push the two bars of the corner apart expanding the size of it creating more tension on the canvas. Antoine-Joseph Pernety (French writer) mentioned the wedges in 1754 and Watin mentioned them in 1773.
The proportional format started appearing at the beginning of the 17th century in Holland. In France, they started to use a proportional format before the 19th century and it is still in use today. There are 3 categories based on the different theories: the Portrait will be built on twice the golden section proportion, the landscape based on the “Porte d’harmonie” rules and the seascape proportion based on the golden section.
1: French translation
2: Non-proportional format
Today, the most common join of the timber bar is a mitred (45' angle) mortise and tenon joint. This way of assembling the stretcher helps with the wedges to open a few millimetres gap creating a better tension. A squared mortise and tenon assembling can create a distortion in the tension, consequently, some damages might appear. Crossbars improve the stability and strength of the stretcher.
At the end of the 19th century appeared in France a bevel on the stretcher to prevent future damage.
Since 1970, Australia converted from the imperial system to the metric system however, we can still find products like stretchers which are still in the imperial system.
Deformations
Tensions
If the tension in the canvas is not perfect, some damage can appear over time. Typical cracks are associated with inappropriate stretch (ladder cracks, garland cracks…). An important tension in the fabric can create some tears.
Bevels
A bevel is a surface that meets another at an angle other than a right angle (cf Collins Dictionary)
For instance, if the stretcher is not bevelled cracks in the ladder will appear on the paint layer above the timber bars.
Wood's weight
When the wood weight is not appropriate to the support, the timber of the frame can twist consequently it will create damage to the support that can be conveyed to the paint layer.
Blog by Maïté Le Mens