Stretchers and Strainers: Glossary

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Author: Heather B. Smith
Date: Submitted January 2007
Compiler: Barbara A. Buckley
=General Stretcher and Strainer Definitions=
Auxiliary Support: The framework over which the painting canvas is stretched. The term usually refers to a stretcher or strainer. Other terms: auxiliary chassis, canvas frame, stretching frame, stretcher, strainer
Bar: A relatively long, evenly shaped piece of some solid substance, such as metal or wood, used as a guard or obstruction or for some mechanical purpose. In reference to stretchers, this is rigid material, commonly wood, that acts as the principal component of an auxiliary support. This component can be joined together in combinations of four or more. Other terms: stretcher member, member
Bead: A rounded edge that is either attached or carved to form a protruding outside turnover edge of the auxiliary support. It is designed to hold the fabric support away from the auxiliary support's members once stretched. Other terms: lip, half round
Bevel: “The inclination that one line or surface makes when not at a right angle” (Flexner 1981, 143); a slight angle on the face of the bar or member closest to the canvas. The slope descends from the outer edge to the inner edge and is intended to maintain a space between the canvas and bar or member. Other term: chamfer
Bevel Joint: See Miter Joint or Simple Miter Joint.
Blind Stretcher: See Panel Stretcher.
Bolt: A metal rod or pin for fastening objects together, which usually has a head at one end and screw threads at the other end.
Bridle Joint: A term more commonly used in carpenter's parlance, it refers to a variant of a mortise and tenon joint in which the mortise is constructed with three open sides, forming a bridle. The tenon is formed by cutting wood away from the front and back of the stretcher bar end so that it slips into the mortise. The tenon is therefore cut to the full width of the stretcher member (Self 2000). Other terms: corner bridle joint, mortise and tenon, slot mortise and tenon, t-bridle joint
Butt Joint: A joint made by abutting two members to one another without overlapping of the two parts (Mayer 1969). The ends are cut at 90° angles to the length of the member. Hardware is needed to secure the joint.
Canvas Frame: See Auxiliary Support, Chassis, Strainer, Stretcher.
Canvas Pliers: A tool used to stretch fabric over the auxiliary support. It is composed of a wide, corrugated head designed to provide a firm grip on the fabric support. A blunt spur centered on one side of the pliers' head serves as a fulcrum, which rests against the wooden members while stretching. There is no known reference to this tool prior to 1889 (Gettens and Stout 1966).
Chamfer: A cut that is made in wood or some other material, “usually at a 45° angle to the adjacent principal faces” (Flexner 1981, 245), intended to place distance between the inner member edge and the stretched canvas. Other term: bevel
Chassis: Another name for the wooden frame on which a textile is stretched (Gottsegen 1993, 298). Other terms: auxiliary support, canvas frame, stretching frame, stretcher, strainer
Continuous Tension Stretcher: A stretcher first developed in the mid-nineteenth century intended to provide constant, even tension. Depending upon the patent, the stretcher framework is most commonly wood or occasionally metal. Continuous tension is created by a variety of automatic spring mechanisms and/ or manually adjustable devices. Most designs adjust to movements within the stretched object automatically, without external manipulation. More complex stretcher designs function to eliminate concentrated stress at corners by distributing tensioning devices throughout the stretcher structure. Earlier designs are tensioned at the corners only.
Corner Braces: Supplementary pieces of wood generally secured to the reverse of a strainer, in the corners, to provide additional support and prevent rotation of the strainer bars. Other term: corner reinforcements
Corner Bridle Joint: A bridle joint in which two stretcher members are joined at their respective ends to form a corner.
Cross Bar(s): Additional horizontal or vertical bar(s) added to strengthen an auxiliary support stretcher or strainer. Other terms: cross brace, cross-member
Dovetail: A flaring mortise and a flared tenon making an interlocking joint between the two pieces. The sides slope in both the receiving mortise and the tenon. The slopes are away from the exterior of the mortise, creating a lip that helps secure the tenon in the mortise slot. (Only allows for expansion in one direction at each stretcher corner.)
Expansion: The act of increasing a stretcher's dimensions, thus increasing fabric tension.
Expansion Bolt Stretcher: A stretcher with turnbuckles that function as tensioners inserted at joints.
Fastener: Hardware used to attach two components firmly or securely (e.g., canvas to auxiliary support or two parts of a fixed joint), usually tacks, nails, or staples; also thumbtacks, lacings, etc.
Half-lap Joint: A joint created when parts of two members overlap. Overlap is usually one-half the thickness of each bar or member.
Hardware: Metalware used to attach two or more components firmly or securely. Usually tacks, nails, staples, also thumbtacks.
ICA Stretcher: Intermuseum Conservation Association Stretcher. See also Continuous Tension Stretcher.
Joint: The point at which two or more members of the auxiliary structure meet. (Cross-reference joint types: butt joint, half-lap joint, mortise and tenon joint, miter joint.)
Keys: Small wedges inserted into slots at the inner corners of a stretcher that are used to expand the stretcher. Other term: wedge
Lacing: Method of stretching canvases prior to the general adoption of tacking. String yarn, twine, etc., is pulled through the edges of the canvas and is used to tighten the canvas over the stretcher by threading through opposite sides of the canvas across the reverse of the stretcher system. Use of this technique dwindled in the 18th century. Modern usage of this term means creating tension without tacking. Other term: Dutch Method
Lip: A rounded edge that is either attached or carved to form a protruding outside turnover edge of the auxiliary support. It is designed to hold the fabric away from the auxiliary support's members once stretched. Other terms: bead, half round
Member: A relatively long, evenly shaped piece of some solid substance, such as metal or wood, used as a guard or obstruction or for some mechanical purpose. In reference to stretchers, this is a rigid material, commonly wood, that acts as the principal component of an auxiliary support. This component can be joined together in combinations of four or more. Other term: bar
Miter Joint: A joint between two bars or members meeting at an angle in which each of the abutting surfaces is cut to an angle equal to half the angle of the junction, usually 45° and 90° respectively. Other terms: simple miter joint, bevel joint
Mortise: A hole, groove, or slot into or through which another part of any arrangement of parts fits or passes. In reference to stretchers, this is usually a rectangular cut into a piece of wood or other material to receive a tenon. Mortise types: closed or blind mortise, wedge mortise, double fork mortise, simple or open mortise
Mortise and Tenon Joint: A joint consisting of two principal parts; a tenon is the projecting component at the end of a member, which is inserted into the mortise, the receiving component, a slot in an adjacent member. Other terms: tongue and groove
Non-rotary Expansion: A term used for stretchers adjustable only in one direction at each corner. The stretcher is constructed with a mortise at each end of one bar and a tenon at each end of the perpendicular bar. This construction allows for canvas expansion in only one direction (fig. 126) (Kim 1998).
Panel Back Stretcher: See Panel Stretcher.
Panel Stretcher: A stretcher with a panel inserted within the opening of the stretcher bars behind, but not touching, the canvas. The panel is usually composed of wood, fiberboard, or cardboard. An American invention dating to the 19th century. Other terms: panel back stretcher, blind stretcher
Peg: A small round dowel.
:
::::::FIGURE 126 Non-rotary expansion
:
::::::FIGURE 127 Rotary expansion
Pin: See Peg.
Pliers: See Canvas Pliers.
Rotary Expansion: A term used for stretchers only adjustable in one direction at each corner. The stretcher bars are constructed with the mortise at one end of the bar and a tenon at the other end. The stretcher configuration allows for canvas expansion in one direction at each corner, but the expansion of adjacent corners is rotated 90°. This type of expansion promotes the formation of a parallelogram configuration; corners are no longer at a 90° angle, stressing the canvas and paint systems (fig. 127) (Kim 1998).
Shattuck Key: A metal key that allows for simultaneous adjustment of both members of a stretcher joint. Patented in 1883, the Shattuck key is only one example of many similar patented metal plates. Other terms: canvas-stretcher, patent metal plate
Simple Miter Joint: A joint made with two members that do not overlap. The ends are cut at 45° angles to make a corner. Fastener or adhesive is needed to secure the joint.
Straight-end: The end cut of a bar or member that is at a 90° angle to its length.
Strainer: A rigid frame usually composed of wooden members, with fixed, nonexpandable corners over which a painting canvas is stretched. The corners are usually fixed with nails, screws, dowels, glue, pegs, or other types of hardware.
Stretcher: A rigid frame usually composed of wooden members, with expandable corners over which a painting canvas is stretched. Other terms: auxiliary support, auxiliary chassis, canvas frame, chassis, stretching frame
Stretcher Bar: See Bar
Stretcher Cleats: Metal wedges that slide on screws fastened to the mitered corners of a strainer. They spread the corners of the strainer and angle the face of the fabric away from the inside edges of the bars(Gottsegen 1993, 38). These cleats allow a strainer to be converted into an expandable system. Other terms: cleats, mechanical screw tensioners
T-bridle Joint: A bridle joint that joins the end of one member to the middle of another. In stretcher construction, when cross members are joined to any of the four principal outer stretcher members at points along their length, the front and back faces of the outer member may be cut with rebates that fit into a bridle on the end of the cross member.
Tacking Edge: The section of canvas that extends onto the outer edge and/or the verso of the stretcher or strainer where the canvas is attached. Other terms: tacking margin, tack-over edge, foldover margin, turnover edge
Tenon: A projecting component at the end of a member for insertion into a mortise to make a joint.
Tensioners: See Stretcher Cleats.
Turnbuckle: A rotating link or sleeve with internal screw threads at each end generally used to tighten the ends of a rod or cable. They are used to close or open joints. This can alter the fabric tension.
Turnover Edge: See Tacking Edge.
Wedge: See Keys.
=References=
Flexner, S. B. 1981. The Random House dictionary of the English language.
Gettens, R. J., and G. L. Stout. 1966. Painting materials: A short encyclopedia. New York: Dover Publications.
Gottsegen, M. D. 1993. The painters handbook: A complete reference. New York: Watson-Guptill Publications.
Kim, Kennis K. 1998. Unpublished teaching handouts.
Mayer, Ralph. 1969. A dictionary of art terms and techniques. New York: Thomas Y. Crowell Company.
Self, C. 2000. Cabinets and Countertops. New York, New York: McGraw-Hill.
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