The canvas of your painting won't warp, but the wood stretchers will, and once they do there best recourse is replacement. Luckily, you can replace one or all four stretcher bars with stretcher bars from the same manufacturer. The stretcher bars are interchangeable, so you just need to select bars of the same size. You can avoid having to replace warped bars by keeping the paintings away from water when you store them, stacking them in a vertical position and not placing other objects on or against them in a manner that could bend the wood of the stretcher bars.
Things You'll Need
- Blanket or similar pad
- Needlenose pliers
- Flathead screwdriver
- Staple gun
- Stretcher bars (sized to match warped bars)
- Rubber mallet or small hammer
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Lay the blanket on a flat, firm surface. A table is best and easiest, but the floor is fine as well.
Place painting face down on the blanket. The stretcher bars and staples holding the canvas will be visible on the backs of the stretcher bars.
Remove the staples with the pliers. If you have trouble getting a grip on them, gently slide a small flathead screwdriver (or similar pointed tool) under the staple and pry upward. Be careful not to slit the canvas.
Lift out the stretcher bars once the staples are removed. The bars will remove in one piece, like a rectangular frame. Leave the canvas on the blanket.
Using the mallet, tap gently on the inside of the stretcher bars, and take out warped bars.
Replace warped bars with bars of the same measure. Align the slot on each stretcher bar with the slat protruding from the corner of the other bar and push the ends of the bars together to make a right angle. Tap the bars together gently for a tight fit.
Slide the stretcher frame with the replaced bars back into place on the back of the canvas. Restore the canvas to its original position by wrapping the edges around the stretcher bars.
Staple the canvas to the back of the stretcher bars, in the same way it was attached prior to replacing the warped pieces. A gentle pull before stapling keeps the canvas taut without being overly tight.