How to Tighten a Painting with Canvas Tightening Keys
By: George Baxter on 30/09/2009
Over time the canvas material on a blank canvas or painting a can lose tension over the stretcher frame due to lateral shrinkage of the stretcher bars. This is caused by a reduction in the moisture content of the timber. This effect is minimized with buying canvases which are constructed with kiln dried stretcher bars.
Caution: If the painting which requires tightening is of financial or sentimental value it would be wise to take it to a professional framer to be tightened as the following methods, if done incorrectly, may damage the stretcher frame or canvas.
Tightening the Canvas a Water Spray
If the canvas is only slightly loose the material can be tightened by spraying a fine spray of water onto the reverse side of the canvas and allowing it to dry. This method is unlikely to work on a very slack canvas in which case, tightening keys may be used to fix the problem.
The tightening keys are usually made of wood or plastic in superior and less expensive stretched canvases respectively. These keys are the eight little wedges usually kept in a small plastic packet attached to the inside rim of one of the stretcher bars. Although with some canvases the keys are already placed in each of the stretched canvas's four corners.
Using the Keys
If the keys have not already been positioned into the four corners gently push them into the slots provided. Following this, lodge them further using reasonable amount of pressure working successively from one corner to the next. It is important that the same amount of pressure is used on each canvas tightening keys as differences in the pressure applied would result in a distorted canvas frame.
Flip the canvas over and check the tightness of the canvas material. If the material is not tight enough - this sometimes happens with large stretched canvases or canvases built with a heavy weave material weave material - you may use a small mallet to apply more pressure to each of the keys in turn.
Working on one key at a time, position the wood on the periphery of the tightening key, take the mallet and lightly tap all eight canvas tightening keys. It is important to mention that great care should be taken when using this technique as too much force would split the stretcher bar. If this happens the painting would require to be stretched again on a fresh stretcher frame.
Canvas keys, used correctly result in canvases that are more rewarding to paint on and can also drastically improve the appearance of a finished painting. If you would like to reduce the chance the frames of your finished paintings becoming loose try using Canvases constructed with kiln dried stretcher bars.
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