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Canvas wedges

... the mystery is explained ... (!)

Once or twice before, this particular question has been posed to me, since, “…if a canvas is stretched properly in the first place, surely it wouldn’t require wedges?”

This is true to a degree, but ultimately dependent on a number of factors, including the size of your work (dimensions of the canvas), the chosen frame profile (depth), your medium and style, whether it is due to be transported anywhere and even where you are located!  Room temperature changes (caused by sunlight, cold or humidity) can affect the fibres of your canvas – and as it becomes heavier, it may move and loosen.

Wedges / Spacers / Chocs or Keys –are adjustable “wedges” of wood that are fitted into the corners of canvas frames – (8 wedges for each frame, and two per cross bar.) used for “re-tightening” your canvas should it have slackened (become loose or ‘bouncy’) over time / transit / temperature or simply because of pressure applied to it during the painting process. This is particularly true of larger, box frames (38 mm). 

Most pre-made, cheaper canvasses have “slots” cut into them (where wooden or even plastic wedges are supposed to go) and the wedges themselves supplied separately – leaving you with the (very intricate in some instances!) job of fitting them into their ‘designated spaces’ before being able to tap them in. However, we used a special dovetailing system, which provides for the wedges to be pre-fitted at all the necessary points – this also alleviates some of the stress of ensuring that the tightened canvas has equal tension all round and that they don’t splinter or crack the corners of the frame when you are tapping them in (a common complaint I hear time and again).  We use only imported, kiln-dried (so most of the moisture has been removed) Obeche timber, and since it is not free, the tendency for the wood in the frames to split is entirely eliminated (a common problem in frames made from timber containing ‘knots’)

Our handmade wedges actually work! And, we are one of very few (if any) local suppliers that are able to manufacture box frames with a wedge system – right up to a profile of 50mm.  In addition, and unlike other systems, there is little to no chance of damaging the canvas when you hammer the chocs in, since they are designed almost as a unit, unlike their often sharper (and damaging to the canvas) counterparts.

If you flick the centre of your canvas with your fingers once your painting is dry, and it vibrates like a drum membrane – tightening is good. The less vibration, the more tightening required.

Some tips when using your wedges:

- If your canvas is unprimed, don’t use the chocs until priming is complete, since priming also makes the canvas more taut.

- With a rubber hammer, gently tap the end of both wedges into each corner for smaller canvasses, working your way around to each corner. (as you tap the wedge, the space at the corner of the stretcher may increase)

-  It is advisable to check the tightening after each wedge position and that you stop once the canvas is taut enough – once the wedge is embedded, it can’t be removed and can create too much pressure, warping your frame.

- For larger canvasses, you need to expand the facing stretcher bars first, in order to keep the tension on the canvas even, i.e tap the wedges that push one of the stretcher bars in one direction, then rotate the canvas and do the same for the wedges pushing the opposite bar, in the opposite direction. Repeat for the other sides.

- It is never a good idea to tap too hard, for obvious reasons, since you always run the risk of overcorrection or the wood splitting – tap means “tap” (not bludgeon in!), even if you go around a second time.

Optimal storage tips to extend longevity of your work:

Keywords are: COOL and DRY

Always try and avoid:

- Direct sunlight or changes in temperature

- Leaning panels and stretchers against walls and directly on the floor (use blocks to raise them)

With regards product – we manufacture wedges for stretchers (23mm profile) and boxes (38mm up to 50mm).

With regards pricing, the wedges-system is literally loaded with 10% on the price of the standard stretcher or box, to give you an idea of what these types of canvas cost.

Please contact me directly if you have any further questions in this regard – I just thought I would share since information is always king!  bronwyn@eandtcanvasses.co.za

- b