Know What’s In Your Fabric: Burn Test for Fibre Classification and Identification
Have a mystery fabric on your hands? It’s hard to know what to make with or how to care for a fabric with an unknown fibre content.
That’s where the burn test comes in – different fibres burn differently, so if you’re feeling adventurous, a little flame can tell you a lot about your fabric.
How to Do the Burn Test on Fibres and Fabrics
Before we get into the details of how to identify each type of fibre, here’s how to do the burn test on your fabric:
- First, cut a small square (5-8 cm) from the corner of each fabric you want to test
- Gather your supplies: tweezers, a candle or lighter, and a tray or plate
- Make sure to do this test over your tray or plate to prevent accidentally burning your countertop
- Hold your fabric with the tweezers and light one corner either with your lighter or by placing it over a lit candle
- Pay attention to these details as you allow your fabric to burn:
- How does it smell as it burns?
- How does it react to the flame – does it start burning immediately or curl up when held to the flame?
- Does it melt or turn to ashes?
- What does the smoke look like?
- If you pull the fabric from the flame, does it keep burning or does the flame go out?
- Once your swatch is fully burned up, what do the remnants left on the plate look like?
How to Identify Different Fibres
Next, we will detail a variety of fibre types and how they react to the burn test. You can use this section of the guide as a reference while burning your fabric swatches to help identify the fibre content.
Vegetal fibres are those originating from natural plant materials that are not highly processed, cellulose-based semi-synthetics.
The most extensively used plant-based fibre in the world, cotton is made from the fluffy material surrounding the seeds of a cotton plant. It makes for comfortable, breathable, and soft fabrics that can be used in a wide variety of clothing and home décor projects.
When held to the flame, cotton will immediately catch fire, then scorch and burn up quickly with a yellow flame. When the flame is put out, a yellow-orange afterglow will be visible. It will smell like burning paper as it smolders. The ashes that remain after burning will be light gray, very fine, and easy to crush.
Also known as linen, flax fibres come from the stalks of flax plants. Linen fabrics are breathable, durable, and absorbent.
When a burn test is performed on linen fabric, the results will be very similar to cotton, but with a few key differences. It catches fire less quickly and burns up a bit slower than cotton. It also has a smell that is more like burning wood or leaves than paper.
Hemp is like flax in that it comes from the woody stalks of plants – in this case, hemp plants. Similar to linen, hemp fabrics are extremely strong, breathable, and absorbent.
Hemp fabric will also perform very similarly to cotton in a burn test – igniting quickly and burning rapidly with a bright yellow flame. However, the smell will be more like linen with a burnt wood and leaf odor. In addition, hemp will not have any afterglow once the flames are extinguished.
Jute is a fibre harvested from the stalks of two plants native to India: Corchorus olitorius and Corchorus capsularis. Jute is a coarser plant-based fibre and is typically used in home décor and other non-clothing items.
When burned, jute will have many of the same characteristics as hemp. It will catch fire quickly and burn with a yellow flame. It will also have the same wood/leaf smell and light gray ashes after burning. However, unlike linen and hemp, it will not shrink away at all when first exposed to the flame.
Ramie fabrics are made from fibres collected from the stems of Chinese nettle plants. They are very similar in appearance and feel to linen, except with a silkier sheen to the fabric.
If exposed to flame, ramie will burn almost identically to cotton – it will catch fire immediately and burn with a steady yellow flame. It will also produce fine, easily crushable, light gray ash. They key difference is the smell – it tends to have a woodier smell like linen, hemp, and jute.
Bamboo fabric, as the name implies, is made from bamboo plants. It is a luxuriously soft fabric with a beautiful drape.
In a burn test, bamboo fabric will burn quickly with a yellow or orange flame, generally darker than the bright yellow flame of the other vegetal fibres we have discussed. In addition, it will have a burnt paper smell similar to cotton. The ash will differ from the fine, gray ash of the other plant-based fabrics – it tends to be coarser and more varied in size.
Natural animal fibres are those made from materials taken from animal-based sources.
Wool is a fibre shorn once a year from sheep. It can be made into durable, breathable, and weather-resistant fabrics.
Wool is somewhat fire resistant, so will ignite slowly and will curl away from the flame before catching fire. The fabric will burn very slowly with an orange flame and dark smoke, and when removed from the source of fire, it will almost immediately stop burning. Burning wool will smell strongly like charred hair or feathers. The ash will be coarse, dark in color, and easily crushable.
Cashmere is an extremely soft and luxurious fabric that is made from fibres shorn from certain breeds of goats.
In a burn test, cashmere will perform identically to wool. Because of this, the feel of the fabric will help you distinguish between wool and cashmere. Cashmere will be much softer to the touch and usually will have more small fibers sticking up across the surface of the fabric, giving it a “furry” appearance.
Alpaca fabric is woven from the long, fine, soft fibres shorn from Alpacas. It produces a very soft, durable, and insulating fabric.
When first exposed to flame, alpaca will react similarly to wool and cashmere; it will curl up and catch fire slowly. However, once alpaca fabric ignites, it will burn quickly with an orange flame. In addition, when pulled from the fire, it will continue to smolder and burn, unlike wool and cashmere. The smoke and ashes will have the same dark look and burnt hair smell as wool.
Silk is an extremely strong, durable, and luxurious textile created from fibres taken from silkworm cocoons.
It does not burn well, so when held into a flame, silk will curl away from the fire and have difficulty igniting. It will mostly smolder and sizzle, rather than producing a visible flame. When pulled out of the fire, it will quickly stop burning. Burned silk will also have an odor reminiscent of burning hair or feathers. The ash will consist of small dark beads that are soft and easy to crush.
Cellulosic man-made fibres are created from wood pulp that is chemically treated and processed to form usable fibre strands that can be woven or knitted into fabric. They are often referred to as semi-synthetics.
Viscose is a semi-synthetic fabric made from a viscous liquid wood pulp collected from various trees and other plants. This fabric is breathable, silky, and has a beautiful drape.
Viscose will catch fire quickly and rapidly burn up (even faster than cotton) with a yellow flame. As it burns, it will give off a burning paper smell and will leave a small amount of light gray ash, almost completely burning up.
Acetate is another fibre created from liquified wood pulp, however the chemical reactions used to create it are different than those used to form viscose. It has a similar look and feel to viscose but tends to be less absorbent.
In a burn test, acetate will burn quickly and continue melting even after the flame goes out. The smoke produced by burning acetate is dark black and smells like vinegar. The ash consists of hard, melted beads that can not be crushed.
Lyocell (also known as Tencel), is another fabric made from wood pulp, but it is made from hardwood trees like oak and birch. It creates a soft, silky, cotton-like fabric.
When placed into the flame, lyocell will catch fire and burn slowly, gradually dissolving into nothing. It does not leave any melted bead or ash.
Fully synthetic man-made fibres are created through chemical reactions and are not at all based on natural plant- or animal-based materials.
Polyester fabrics are versatile, durable, wrinkle-resistant synthetics. The main downside of polyester, other than the negative environmental impact of its production, is that it is not breathable or sweat-wicking.
Polyester ignites and burns quickly, shrinking and melting away from the flame. It may flare up, and when it does, the flame is orange in color. When removed from the fire, it may continue to melt slowly. As polyester burns, it emits a sweet, fruity, chemical smell. It does not leave ash, but rather a small, dark, melted bead that is not crushable.
If you are looking for a more sustainable alternative to traditional polyester fabric, we have a selection of recycled polyester and polyamide fabrics. For example, check out this heavy-weight recycled polyester or this light-weight biodegradable polyester. You can even make environmentally friendly swimwear with this biodegradable polyamide swim fabric, or a fancy dress with this recycled polyamide tulle.
Nylon is another synthetic man-made fibre, formed by a different chemical reaction than polyester. Nylon fabrics are durable, hard-wearing, and water resistant.
When held to the flame, nylon quickly burns and shrinks away from the fire. Once pulled from the flame, the fibres will continue to slowly melt and drip. This fabric will smell oddly of celery while burning and will leave behind uncrushable, round beads.
Spandex is another synthetic fibre, especially useful for its extreme elasticity. Spandex is often blended with other fibres to give fabric stretch.
Rather than burning with flame, spandex tends to slowly melt and does not shrink away from the fire. Once the flame is extinguished, it continues to melt and gives off a sharp, bitter smell. The ash that remains will be dark black, soft, and sticky.
Acrylic fabrics are strong, durable, and insulating – they are often used in outerwear and furniture.
In a burn test, acrylic will shrink away from the flame and burn rapidly with a whitish-orange flame. It will sputter, flare up, and drip as it melts. The smell of burning acrylic is not a nice one – often reminiscent of charred meat or fish. The ash will consist of hard, irregularly sized, melted beads.
PVC vinyl fabrics are tough, abrasion-resistant, thick, and often stiff. They can be used for a wide variety of applications from specialized clothing to vehicle components.
When exposed to flame, PVC will not catch fire easily and will shrink away from the flame and continue to extinguish. While held over the fire, the flame will be yellow and may periodically turn green. It will give off a strong acidic smell as it burns.