Fulling is a process used to treat woven or knitted wool textiles; the resulting fabric is said to be “fulled” or “felted.” After fulling, textiles are smaller, thicker, and much more durable, with the added bonus of being largely waterproofed. Fulling is an ancient process, and examples of traditional fulled textiles can be found all over the world, from the thick felted tents of Tibet to the soft felts worn in the Alps to insulate the body from the cold.
You may hear fulling referred to as felting, tucking, or waulking. All of these processes involve three basic steps: cleaning the fabric, agitating it, and then stretching it so that it will take on a desired shape. Depending on how heavily the fabric is fulled, it may be relatively lightweight and strong, or much heavier and stiffer.
The process of fulling appears to have originated in Asia, and spread from there to the rest of the world. In the first step, the fabric is exposed to hot water and soap or various chemicals to remove dirt and impurities, and then it is agitated. Gentle agitation results in a lighter felt, while heavier agitation will generate a thicker cloth. Historically, people walked on fabric in huge tubs to full it; commercial fulling is usually accomplished with heavyweight hammers today.
The moisture, friction, and heat cause the scales on the wool to open up, and then to interlock, creating a dense mat. This process is irreversible; once fabric has been fulled, it can't go back. It can, however, be fulled even more, which is why wool fabrics have to be handled carefully in the wash. Anywhere from five to 20 percent of the volume of the fabric may be lost during the fulling process.
After fulling, the wet fabric must be stretched or “blocked” on a rack. If it is not stretched and held taut while it dries, the fabric will become misshapen. Stretching pulls it into a specific shape, and ensures that the fabric will hold that shape, even if it is severely abused. Felted shoes, hats, and similar garments can be blocked with specially designed expandable inserts, while flat sheets of fabric are stretched on tenterhooks for the drying process.
Some crafters who work with wool like to full their crafts at home to create felted projects. Patterns for knitted or woven garments intended for fulling can be found in many craft stores, and it is also possible to adapt a regular pattern. Fulled fabrics and garments are also available commercially.