How do I tighten a stretched canvas that has loosened?

Over time a canvas can become baggy or wobbly due to changes in the environment. Here are 2 easy and non-damaging DIY fixes that don’t require you to spend money on getting it professionally re-stretched.

By Saira Kalimuddin-May

27 May 2022

Sometimes a stretched canvas can become loose or baggy or wobbly. Sagging can happen because of differing environmental conditions and changes in the levels of humidity.  Or sometimes a dent can occur because the canvas has been leaning against something (usually another picture) that has caused one part of the canvas to protrude.

There are two main ways to tighten a stretched canvas yourself.

  1. The Wetting-Drying Method

The first is to lightly rub a wet sponge over the back of the canvas (do not do this on the front!). Rub it until you feel moisture soak into the weave of the canvas. Alternatively, you can use a  spray bottle to mist water over the back of the canvas. Then leave the canvas to air dry and it should tighten once it has dried.

If it is still not tight enough, repeat this wetting and drying process until it is tight enough.

The reason this method works is that it shrinks the fibres of the canvas (which relax over time) and causes it to contract and tighten. 

This same method applies to dents in the canvas. Use this wetting process on the dented area and it should contract and the dent will disappear.

This video on YouTube is worth a watch if you need a more visual explanation: https://www.youtube.com/watch?v=s5Tix47q8S0

2. Canvas Keys Method

The second method to tighten a stretched canvas is to look for the canvas keys at the back of the canvas (see image below).

Use a hammer to lightly tap in the keys until the canvas tightens. 

Canvas keys are thin wedge-shaped pieces of wood or plastic, that when placed in the corner slots of the stretchers, will tighten and bolster the frame itself, therefore, tightening the canvas stretched on it.

Use a hammer to lightly tap in the keys until the canvas tightens. 

If both these options don’t work or if the artwork is very expensive, you will need to take it to a framers to get it professionally restretched. 

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