FIBER SHAPE AND SHEEN

How fiber shape affects sheen

Most of the threads we use when sewing and quilting are round and smooth, as a result of twisting multiple strands (plies) together. We often think of thread consisting of only two or three strands (2-ply or 3-ply) twisted together. In the case of spun threads such as cotton or spun poly, it may be that simple, but with multi-filament threads such as polyester, silk, or rayon, it gets a little more complicated. A 50 wt. 3-ply polyester thread such as So Fine! has three strands twisted together, but each of those three strands, or plies, are made up of many micro-strands twisted together. High-quality threads have a high number of micro-strands, such as 48, in a single ply. Lower quality threads will have fewer micro-strands. There is a correlation with strength in the number of micro-strands that make up a single ply.

Smooth fibers such as silk, multi-filament polyester, and rayon have a higher sheen than non-smooth fibers (such as cotton and spun polyester). However, even within the smooth fiber category, there is a wide range of sheen or luster. The visible reflection from a high-sheen thread is the result of each individual micro-strand of fiber reflecting light, and the shape of the individual fibers determine how light is reflected.

Round fibers: Regular multi-filament polyester threads such as So Fine! #50, Bottom Line, and MicroQuilter are made from round fibers that are twisted together. As light hits the fibers, it is reflected away from our eyes, which results in a medium sheen appearance.

Trilobal fibers: Magnifico, Fantastico, Nature Colors, Living Colors, Super Brights, and Art Studio Colors threads are made from trilobal polyester fibers. Silk is a natural trilobal fiber. Trilobal fibers have three distinct sides ('tri' = three and 'lobal' = sides). When light hits the fiber, it is reflected back in a direct path, resulting in a high-sheen appearance. Although the individual micro-fibers are trilobal in shape, when multiple strands are twisted together to make the final thread, the end result is a smooth, round, high-sheen thread. Until recently, trilobal polyester fibers were weaker than regular round polyester fibers, so we had to choose between strength or a high-sheen appearance. Thankfully, we now have both. All of Superior's trilobal polyester threads are made from high-tenacity fibers (meaning they are strong) and consist of 192 micro-strands twisted together to create a gorgeous, and strong, 40 wt. thread.

Irregular fibers: Most rayon threads are irregular in shape. Also known as Viscose Rayon, we don't use or recommend rayon threads as they are weaker than polyester fibers and are not in line with the common standards of colorfastness. Trilobal polyester threads cost the same as rayon threads and are a better thread due to their strength and superior colorfastness.