How do they work?
A lot of people ask the question, but what are they used for? It can seem like a mystery. Here is the answer:
– What is in the bag?
The bag contains 8 (or more) small triangular pieces of wood. The wooden wedges are used to adjust the tightness of the canvas.
You should know that stretched canvases are not really « finished ». They must be tightened after painting.
– How does a stretched canvas work?
A stretched canvas is composed of stretcher frames and bars, and all material is assembled with strength in each corner.
If you look closely, canvas wedges have notches in the corners. A corner will have 2 wedges that will be used to make it tighter.
– Why stretch a canvas?
Whilst painting, the artist gradually burdens the canvas with the addition of paint, materials and collages. Over time these changes can affect the tightness of canvases.
Do not also forget that the canvas of a painting is also subject to room temperature changes. These changes can be caused by sunlight, humidity, or cold and they affect the fibers of the canvas. As the canvas becomes heavier it can move and loosen. That’s why this bag of wedges is quite useful!
– How to use wedges for tightening?
– Step by step:
- Using your fingers, insert the wedge into each of the slots (pointing down and long side parallel to the frame).
- With a hammer, gently tap the flat part of the wedge. It is important not to hit too hard so you don’t cause damage to the frame. The wedge will then stretch the space between the two bars of the frame and stretch the canvas.
- Repeat on all corners (+ bars for large canvases).
TIP #1: check the tightening of the canvas after each wedge position. You should stop as soon as the fabric is tight enough; because the embedded wedge cannot be removed once it is inserted and can create too much pressure. The wedges should be used carefully and not stretch the fabric too tight, to avoid too much tension, which could twist or damage the frame.
TIP #2: Some wedges have points that are very sharp and thin. This can tear the fabric. I advise that you cut this wedge if it is too sharp (see the picture below).
– How to tell if the fabric is too tight?
Once your paint dries completely (with your varnish) do a little flick with your fingers at the center of your canvas.
- The canvas vibrates like a drum membrane while remaining in place = good tightening.
- The canvas seems soft and doesn’t vibrate = low tightening.
– How to choose a stretched canvas?
Some brands are already well stretched. You should, however keep the wedges for future use because the fabric tightening may change.
- Cheap canvases may have faults and no wedges, or have very poor tightening. Paintings without wedges are more difficult to recover, especially if the frame is glued together.
- With small sized paintings (6’’x6” or 8’’x8’’) it’s not always necessary to use wedges.
– The canvas that I personally use:
I usually use wedges after my painting is finished (painted and varnished, completely dry).
I only use primed linen canvas on wooden frames. Here are some recommendations of brands that you may find helpful:
- Gerstaecker Excellence Plus Linen Stretched Canvas
- Gerstaecker Classico 2 Linen Canvas
- Gerstaecker Beech Canvases Wedge Set, here
For those who prefer linen canvas, natural, and coated with a transparent primer: Honsell Natural Linen Canvas is a good choice.