A selvage (US English) or selvedge (British English) is a "self-finished" edge of a piece of fabric which keeps it from unraveling and fraying. The term "self-finished" means that the edge does not require additional finishing work, such as hem or bias tape, to prevent fraying.
In woven fabric, selvages are the edges that run parallel to the warp (the longitudinal threads that run the entire length of the fabric), and are created by the weft thread looping back at the end of each row. In knitted fabrics, selvages are the unfinished yet structurally sound edges that were neither cast on nor bound off. Historically, the term selvage applied only to loom woven fabric, though now can be applied to flat-knitted fabric.
The terms selvage and selvedge are a corruption of "self-edge", and have been in use since the 16th century.
In textiles
Definition
According to Hollen, Saddler & Langford, "A selvage is the self-edge of a fabric formed by the filling yarn when it turns to go back across the fabric." In traditional looms, the selvage on both sides of a piece of fabric were manufactured same, whereas in modern shuttleless looms these selvages are low because of cutting filling yarn and selvages looks like fringes.
Different types of selvages are as follows:
Plain selvages. These are like fabric, do not wrinkle and are used in sewing selvage in fabric construction. Tape selvages. These are long and made by ply yarn for strength. These are broader than plain selvages and basket weave is used for flatness. Split selvages. Narrow fabric like towel is woven from two or more sides together and then cutting is done. Later, these cut selvages are hemmed or chain stitched for finishing. Fused selvages. These are fixed by temperature which is made of ribbons which are cut in narrow widths. Leno selvages. These are used on some type of shuttleless looms. In this cut, selvages are locked and narrow Leno weaves are done. Loose selvages generally need tight leno weaves. Tucked selvages. Like Leno selvages, these are done on a shuttleless loom. Machines are used to tuck the cut fabric and fix them.
In woven cloth
In textile terminology, threads that run the length of the fabric (longitudinally) are warp ends. Threads running laterally from edge to edge, that is from left side to right side of the fabric as it emerges from the loom, are weft picks. Selvages form the extreme lateral edges of the fabric and are formed during the weaving process. The weave used to construct the selvage may be the same or different from the weave of the body of the fabric cloth. Most selvages are narrow, but some may be as wide as . Descriptions woven into the selvage using special jacquards, colored or fancy threads may be incorporated for identification purposes. For many end-uses the selvage is discarded. Selvages are 'finished' and will not fray because the weft threads double back on themselves and are looped under and over the warp.
Handwoven selvages vs. industrial selvages
There is a slight difference between the selvages in handweaving and in industry, because while industrial looms originally very closely mimicked handweaving looms, modern industrial looms are very different. A loom with a shuttle, such as most hand weaving looms, will produce a very different selvage from a loom without a shuttle, like some of the modern industrial looms. Also in industry sometimes the selvage is made thicker with a binding thread.
Selvages of fabrics formed on weaving machines with shuttles, such as hand looms, are formed by the weft turning at the end of each pick (pass of the weft thread) or every second pick. To prevent fraying, various selvage motions (or "styles") are used to bind the warp into the body of the cloth. Selvages are created to protect the fabric during weaving and subsequent processing (i.e. burnishing, dyeing and washing) but ideally should not detract from the finished cloth via ripples, contractions or waviness.
In handweaving the selvage is generally the same thickness as the rest of the cloth, and the pattern may or may not continue all the way to the edge, thus the selvage may or may not be patterned. A plain weave selvage is the other option, where the last few threads on either side are woven in plain weave.