If you walk into any embroidery studio on planet earth, you'll typically see them using one of two types of thread:
polyester or rayon.
What is the difference between these two thread types?
Known as viscose in Europe, rayon is a semi-synthetic
fiber made from cellulose that has been treated with alkali and carbon
disulfide. As a fabric, rayon is somewhat breathable and does not trap
body heat. It can simulate a variety of fabric textures, including linen and
silk, and is often blended with more expensive fibers, such as cotton or silk,
to reduce cost.
In embroidery, rayon thread has a high luster, giving the embroidery a nice,
shiny quality. The glossy appearance alone is enough to convince many
embroiderers, both commercial and hobbyist alike, to use rayon thread. High
quality rayon thread is also relatively easy to find. For example, national fabric chains
such as JoAnn's and Hancock's carry small spools of Sulky brand rayon thread.
Polyester is a synthetic fiber made from polymers. As a
fabric, polyester cloth is noted for being relatively uncomfortable. This is
because the fiber is not porous: it doesn’t absorb water well and therefore
doesn’t wick moisture well either. Garments made of polyester feel far warmer than other, natural
fibers. However, polyester also resists wear, tear, wrinkles, shrinking, and
fading better than natural fibers. It is
often blended with other fibers to combine comfort with durability.
For embroidery, you’re only embellishing the garment, so there’s
generally not enough polyester thread to significantly reduce comfort – assuming the
garment is made from a breathable fabric to begin with. High quality polyester embroidery thread also has a
much higher sheen to it than you normally see in either fabric or general
sewing thread. It’s not as shiny as rayon embroidery thread, but it’s still got
enough luster that I’ve had an experienced quilter mistake it for rayon.
Which one do I use?
I possess both rayon and polyester embroidery thread, but I
generally work with just polyester. Why? Because although rayon thread is very
pretty, I think the following three practical factors outweigh its cosmetic appeal:
(1) Rayon is not as color-fast as polyester. It’s a porous
fiber, so it will both absorb and bleed color relatively easily. Rayon can be
dry cleaned, but it should not be bleached or subjected to whitening agents. Polyester is non-porous. It’s difficult to
dye, but once the dye is there, it generally stays put. A good quality
polyester thread, such as Isacord brand, can be boiled!
(2) Rayon burns, while polyester melts. Neither is totally ideal, but if you brush by them with an iron on the hottest setting, the polyester may fuse, but the rayon will singe. I'd, personally, rather see the texture change than have the color char to brown or black. (Always iron embroidery from the back
of the garment.) Also, polyester
can be microwaved without melting, so it takes quite a bit of heat before it can get damaged.
(3) Rayon fibers are weaker than polyester fibers. This
means that the thread is more likely to break on the machine – particularly if
your machine is capable of running at high speeds (industrial machines can get
up to 1000 stitches per minute). Most combination sewing/embroidery machines can
only go a maximum of 500 stitches per minute, so this is less of a problem for
the hobbyist.* Rayon’s weaker fibers also mean that it is not as resistant to
abrasion as polyester thread. If the embroidery is on something that will be
washed and dried multiple times, it’s going to look better longer if it is
stitched with polyester thread.
As a general rule, once I embroider something, it is out of
my hands. I want what I produce to look as good as possible for as long as
possible, so I that’s why I use high quality polyester thread. To be exact, I
use a combination of Isacord brand thread, which is made in Germany,
and Robinson-Anton, which is made here in the USA.**
*If you’re working with rayon thread and find that the
thread is shredding during application, consider loosening the tension, using a
needle with a larger eye, cleaning the tension disks, running the machine at a
lower speed, and/or applying a small amount of sewer’s aid (a silicon-based product)
to both the needle and the thread. Or, you could switch to polyester – it’s
literally twice as strong as rayon, and some brands (like Isacord) are even
**There are a lot of good brands out there. These are just the
ones that I use. Sticking to just one or two manufacturers makes it easier to
acquire a broad pallet of colors without any accidental duplication.
I will also note that
thread manufacturers have made significant progress in thread
technology over the past few years. In the 1990s, all embroiderers used
rayon thread because the polyester thread would stretch, making it
difficult to run through the machines. Thread producers now twist the fibers differently, eliminating this problem.