How to Adjust a Wood Keyed Stretcher Using Wooden (wedges) Keys and Why.

The John Annesley Company

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Why?

• Loose canvas– All fabric expands and

contracts due to hot and cold temperatures. During the course of the day, as the temperature fluctuates, and the fabric expands and contracts. The wood is also expanding and contracting with the ambient moisture in the atmosphere. The force of gravity is pulling constantly. The combination of these forces will cause the fabric to fatigue. This occurs primarily along the edge of the canvas where the canvas and the stretcher make contact.

• To remedy this problem, you have three options:– You can re-stretch the

canvas, which is the best option.

– You can expand the stretcher bar, there by tightening the fabric. A wood keyed stretcher allows for independent expansion in either direction in each corner.

– You can shrink the fabric, making it tighter, by using moisture (water). Each time this method is used, you reduce the elasticity of the fabric.

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Tools and Materials Needed

• Awl• Small Hammer• Side Cutters• Wooden Keys

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N1 Stretcher (face view)

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N1 Stretcher (back view)

The back side has the stapled corners.

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Corner Detail Showing Staples

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Getting Started

• Pry the staples using an awl.

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• Once the staples have been lifted from the stretcher, finish pulling them out with a pair of side cutters.

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Staples Removed

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Corner Detail with Two Wooden Keys

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Detailed Mortise View

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First Wooden Key Inserted

• Insert first key into bottom slot, flat side slides along the inside edge of the stretcher, and into the mortise.

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Second Wooden Key Inserted

• Insert second wooden key into top slot, flat side slides along the inside edge of the stretcher, and into the mortise.

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Making Adjustments

• Gently tapping this key will cause the joint to move in the direction of the arrow.

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Making Adjustments

• Gently tapping this key will cause the joint to move in the direction of the arrow.

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Detail of Joint Spacing

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Overview of Wood Keyed Stretchers• Advantages

– Easily assembled and disassembled using minimal hand tools.

– The corner joints (open mitered, double mortise and tenon) can be expanded independently in each direction.

– Braces can also be keyed with mortise and tenon joints.

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• Disadvantages– Damage can occur to the

painting by striking the canvas accidentally with the hammer while hammering the keys.

– Keys can break, and become lost between the canvas and the stretcher, causing damage to the painting.

– Keys can become lost.