Updated October 13, 2020.
There is so much confusion in the needlepoint world about thread terms and fibers. Partly this is because we use some terms, like ‘thread’ to mean a number of different things (think of it like ‘shade’ when talking about color). Partly it is because many in the needlepoint world advocate using terms differently than the rest of the fiber world uses them.
Today is a good day to define terms in a standard way and then to talk a little bit about the stuff threads are made from.
Fiber is the raw material from which all threads and yarns are made. For example, flax is the fiber from which linen is made. Fibers might need to be processed from their initial, or raw, state to one where it can be turned into thread or yarn. Depending on the fiber this can be simple or complex. Once turned into something that can be sewn, stitched, or knitted it is no longer a fiber; it is a thread.
Threads are fibers that have been processed, usually spun, to become the base unit for creating something used to stitch, sew, or knit. Thread also refers to both the single unit of a cloth (i.e. thread count in sheets) or the stuff as it comes out of the packaging. If you knit, threads are usually called yarns, even if they are the exact same stuff as a needlework thread, but in a larger package.
Threads, in turn, may be composed of strands. A strand is the smallest divisible unit of a thread. Some threads, such as floss or Watercolours, have more than one strand in them. Others, such as Planet Earth Silk, only have one strand and are used as is. If you can separate out part of the thread and it is strong enough to use for stitching, it is a stranded thread, no matter how tightly twisted it may have been when it came out of the package.
Strands are made from plies of the initial spun thread. Plies come from the spinner and are combined into groups to make the strands. Strands can be used to stitch, plies cannot. That because plies usually are not strong enough on their own to stand up to wear. In the process of making the threads we use plies are twisted together (spun) to make a strong useable thread.
Although we talk about ‘plying’ a thread what we actually are doing is separating the strands.
Knowing these terms will allow you to talk about threads with other fiber artists. You will also be able to read and understand thread descriptions from people who make threads. To translate to the non-standard language of many needlepointers, reverse the definitions of ply and strand.
Fibers are defined by their origins and fall into three broad classes: animal, plant, and man-made. Although the fibers in each class differ from each other in many ways, they tend to share similarities in structure that cause them to be dyed by the same type of dye. If you dye cotton (a plant fiber) with a dye made for wool (an animal fiber) you will not get the results you’d like. That’s why the “same’ color of thread in two threads in a line might differ.
Animal fibers come from the animals themselves and are two main kinds. Silk comes from the cocoons of the Silk Moth. Wool comes from the fur of animals, usually sheep. If it comes from an animal’s fur we call it ‘wool’ even though it may be from another animal, such as an alpaca or a rabbit (angora). We still call it wool, even if the animal is not sheared but combed (cashmere is combed from goats).
Plant fibers come from some part of the plant. Cotton and linen are two of our oldest fibers, made since Ancient Egyptian times. Other plant fibers, such as soy yarns, come from more modern processes (tofu manufacture in the case of soy threads). Plant fibers seem to be multiplying in range these days as fabric companies look for alternatives to cotton.
Man-made fibers are everything else. They can range from fibers made from natural sources to ones made from chemicals. The first man-made fiber, rayon, is made from cellulose or wood pulp. Polyester is made from petro-chemicals.There are new man-made fibers popping up all the time. Many manufcturers create brand names for their fibers, even though they might be from a more generic type.
Embroidery thread is a tiny sliver of the textile marketplace and the threads we use are mostly from plant and animal fibers. As time goes on, you can expect to see fibers used to make cloth to filter down first to the knitting market, then to the embroidery market. If you buy threads from small manufacturers (look for them on Etsy) you can often find more unusual combinations.