6 Tests to Identify the Fiber of a Fabric

I try to get most of the fabric that I buy second hand. Whether this is deadstock, fabric scraps, or just thrifted fabric, it often means the fabric is kind of an unknown. I don’t know exactly what it is or what kind of fiber it is. Cotton? Rayon? Polyester? Who knows?

Well different types of fiber have different characteristics. You can make a pretty good guess about the type of fiber (or fiber blend) used in a fabric if you know the qualities associated with it.

By familiarizing yourself with these traits, you can make an educated guess about the fabric’s composition. For example, cotton generally has a soft feel and natural wrinkles, while polyester often sports a smoother finish and resilience against creasing, and rayon is known for being smooth and flowy.

1. The texture of the fabric

The first thing to look at is the texture. Surprisingly, you can tell a lot about a fabric simply based on how it feels. Keep in mind, my written descriptions will only tell you so much. The best way to start learning about fabric is to go out and actually touch many different types. That’s what will give you the best understanding of the tactile qualities of different fibers.

• Cotton or cotton blend: You’ll notice a soft and very slightly fuzzy texture when you run your fingers over cotton fabrics. Cotton blends will vary slightly in texture depending on what fibers they’re combined with. For example, a cotton/polyester blend will be smoother, but will still retain the soft feeling of cotton.
• Polyester or man-made synthetics: These fibers tend to have a smooth texture which can feel almost plastic-like, especially in lower quality polyester fabrics. The slick surface of polyester is a telltale sign of its synthetic makeup.
• Wool: Expect a fuzzy texture with wool, which may range from fine and soft to more coarse depending on the grade of the wool.
• Silk: Known for its luxurious feel, silk possesses a soft texture that is not quite as smooth as polyester but is more pleasant to touch. Silk it not usually slippery to the touch, if a fabric has that slick feel, it’s more likely polyester.
• Rayon and most plant-based synthetics: Falling somewhere between cotton and silk, rayon fabrics provide a compromise with a texture that mimics the qualities of both natural fibers
• Linen: Typically linen has a fairly rough or coarse texture. However, some linen is treated to give it a softer texture that is more comfortable to wear. Even this linen will have a rougher, crisper feeling than other types of fabric.
  

2. How easily does the fabric wrinkle?

Different fibers also have different characteristics when it comes to wrinkling. The ease with which the material creases and the types of wrinkles you see will help you determine the type of fiber that the fabric is made from.

To perform a wrinkle test, crumple up a section of the fabric and hold it in your fist and for about 30 seconds. Then, release the fabric and attempt to smooth it out on a flat surface and see how the fabric behaves.

• Cotton: Cotton wrinkles easily, and tends to have deep creases. When you smooth out the fabric on a flat surface, the smaller wrinkles may lessen, but the deeper creases will remain.
• Cotton/polyester blend: This blend generally resists wrinkling. After the squeeze test, any wrinkles are usually not as pronounced and will often return to a smoother state without much effort.
• Polyester: Fabrics made from polyester fibers do not wrinkle easily. Even after applying the 30-second crumple test, it should reveal minimal wrinkling.
• Wool: While wool does wrinkle, it’s known for its ability to bounce back. After you squeeze the fabric and smooth it out, the wrinkles should start to soften and diminish on their own.
• Rayon: When you squeeze rayon, expect it to show wrinkles very easily, often with both deep and soft creases. The fabric does not smooth out easily.
• Silk: Silk fabric, when subjected to the crumple test, typically ends up with gentle, softer creases. It wrinkles but is more forgiving than cotton or rayon.
• Linen: Linen tends to wrinkle easily with deep creases. However, linen fabrics that have been treated to make them softer will also wrinkle less and have softer creases.

3. Are there any natural imperfections in the fabric?

Natural fabrics often have imperfections that synthetic fabrics don’t.  These are not flaws, but rather inherent traits of the materials that can help you determine what type of fiber you are looking at. 

• Linen will always have slubs, which are small, soft lumps in the yarn at irregular intervals in the fabric.
• Wool will have an irregular fuzzy texture. This fuzziness is due to the natural crimp of wool fibers. The finer the type of wool used to make the fabric is, the less of a fuzzy texture the textile will have.
• Some types of silk will have natural slubs, particularly the varieties like Dupioni or Shantung.

Unlike other natural fabrics, cotton usually does not have many imperfections; you’ll recognize it more easily by its texture. 

It’s also important to understand that rayon and polyester can be created in ways that mimic natural fabrics, including the slubs of linen or silk and the fuzzy texture of wool. So, it’s not always possible to determine the fiber content just based on the fabric imperfections.

4. What is the drape of the fabric

Different types of fiber have different types of natural drape. The drape of a fabric indicates how it hangs or falls when utilized as a garment or furnishing. This quality can range from stiff and structured to very flowy. While the weave of the fabric plays a large role in how the final material drapes, the fiber used will also affect the drape of the textile.

• Cotton: cotton fabric tends to have a more structured drape. It does not cling to the body and often retains its shape.
• Rayon: This fiber often exhibits an extremely flowy drape, which gracefully conforms to body contours.
• Wool: Wool fabrics can have a moderate to heavy drape.
• Polyester: There is considerable variation with polyester since its ability to mimic other fabrics allows it to be engineered for specific draping qualities. However, it more often has a moderate drape that is a balance between flowy and structured.
• Silk: The drape of silk fabric can vary a lot as well, but usually falls into one of two categories; it can be very flowy, draping elegantly, or very structured, offering a stiff, crisp silhouette.
• Linen: While not quite as graceful as rayon, linen fibers do tend to give fabrics a fairly flowy drape.

5. Does the fabric stretch? How much? (to see if there is spandex/elastane fibers)

When trying to determine if a fabric contains a percentage elastic fibers (like spandex or elastane), you can evaluate how much it stretches. Usually, these elastic fibers only make up about 5% to 15% of a fabric’s fiber content, but even this small amount will alter the elasticity of the final fabric.

• Woven fabrics should not have a noticeable stretch. If you find that your woven fabric does stretch, this is a strong indication that it contains spandex or elastane.
• Knit fabrics are a little trickier because they are constructed in a way that does allow them to stretch. However, knit fabrics with spandex will typically stretch much more that knit fabrics without. If your fabric can stretch more than 200-300%, it likely has some spandex in the fiber content

6. Use the fabric burn test

The way to get a much clearer idea of the fiber in a given textile is to perform a burn test. This isn’t something I necessarily recommend, since it means you have to burn the material and make a section of it unusable, it’s a fire hazard, and regularly inhaling fumes from synthetic fibers is not great for your health.

But, if you really need to know what the fiber is, the burn test is the most accurate method without doing actual chemical testing on the fabric. This test involves observing how a fabric sample reacts when exposed to a flame. It tests whether the fabric burns, melts, how long it sustains a flame, what it smells like, and so on. 

I’ll go over the basic information here, but if you want a lot more details, I recommend checking the book Textilepedia (pages 58/59). That’s one of the best resources I’ve found for beginners who are trying to understand fibers and fabrics.

Note: Practice good fire safety measures. Hold the fabric samples with tweezers to prevent burning your hands, and make sure you know where the fire extinguisher is just in case. You will also want to do this over a sink or other non-flammable surface.

• Cotton: Cotton fibers burn quickly with a yellow flame, and will smell kind of like burnt paper.
• Rayon: Rayon burns very quickly and kind of dissolves while it’s burning, leaving very little ash. It will also smell like burnt paper.
• Wool: Wool burns slowly and will often self-extinguish instead of burning continuously. It will smell like burnt hair or fur.
• Polyester: Polyester burns with an orange flame and melts (because it’s plastic). It will have a chemical scent when burning.
• Silk: Silk fibers will burn and sizzle out slowly, smelling like burn hair or feathers.
• Linen: Like cotton, linen will burn quickly with a yellow flame, but it will smell more like burnt wood or leaves.