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How to Use Canvas Wedges
Wedges are included with pairs of Standard, Premium, Gallery, and Contract stretcher bars. They allow the join of the stretcher frame to open slightly, re-tensioning the canvas and reducing slack. The size of the wedges vary depending on the stretcher bar being used, the bigger the bar, the bigger the wedge. The shape may also vary a little for the best fit into the slotted corners of a stretcher bar frame.
Insert wedges into slotted stretcher bars after the canvas has been fixed to the frame.
Wedges have many uses including:
- Finishing a hand stretched canvas. They provide that last bit of tightening to ensure the canvas is taut. Do not engage canvas wedges until the priming of the canvas is complete, as priming a canvas can cause it to shrink.
- Tightening a ready made canvas that has lost its tension over time. The tightness of a canvas it naturally relax over time. Often only a couple of millimeters is needed to make a loose canvas taut again.
- Tightening a canvas that was taut before painting but has now began to sag from the weight of the paint and the pressure of the artists' brush. Wait until the painting and finishing of the canvas is complete and dry, then assess whether a re-tightening is needed. Take care when tightening with wedges as certain surfaces of a painted canvas can crack if over tightened.
- Re-tension a finished canvas that has lost tightness over the years. The temperature and humidity of the room in which the painted canvas is displayed varies from day-to-day, season-to-season. These fluctuations in conditions can cause a canvas to go slack over time. Inserting wedges allows the canvas to be tightened, combating the slackness. Always take care when tightening a finished canvas, particularly oil paintings, as stretching can crack the surface.
How to insert wedges
Wedges can only be used with slotted stretcher bars. These are stretcher bars that have slots notched out at either end. Slots allow for the wedges to be inserted and tapped into the frame, pushing the stretching bars apart at the corner. This in turn stretches the canvas by a few millimetres.
With the back of the canvas facing up, place one wedge into each slot of the stretcher frame. Gently tap the wedges with a soft faced hammer, too much force could split the wedge. Take care when tightening a finished canvas as stretching can crack the surface. There will be a total of 8 wedges per stretcher frame, two in each corner. Work around the corners tapping the wedges so that the canvas starts to gently stretch evenly.