Sometimes a garment can be associated with something unpleasant because of how it smells. In this article we look at some of the more common causes of smells in textiles to show how they can be eliminated and/or prevented.
We will begin by dividing smells in textiles into two categories, based on the causes: natural smells and chemical smells.
- Natural smells
Everyone has definitely smelt what is known as “body odor”.
Let’s find out more about body sweat.
Firstly, the expulsion of sweat vapor is the precious mechanism that our body uses to dispel excess heat as caused by physical effort or the sun.
Thermodynamics teaches us that a certain amount of heat is required in order for the evaporation process to take place, and sweat, which is simply the evaporation of sweat, takes the heat it needs from the body, and cools it. As soon as vapor from sweat enters into contact with the air outside the body it condenses into drops, forming those typical drops of sweat.
It should be pointed out here, that sweat is not malodorous. So why is it that if we don’t wash a sweat-drenched T-shirt, it soon gives off a very unpleasant smell?
The cause is skin bacteria which proliferate quickly on the textile, and which are able to bio-transform some of the chemical substances in the skin. In particular some bacterial strains (e.g. Proprionibacteria, Staphylococci sp.) are responsible for breaking down the skin lipids and others (Corynebacteria) can break down the steroids.
Both these mechanisms lead to the formation of bad-smelling volatile substances, first among these isovaleric acid. These substances, which are absorbed by the textile fibers, are the cause of that typically unpleasant “body odor”.
It is interesting to note that the intensity of the smell depends not only on the quantity of bacteria but also on the type of fiber: synthetic fibers in particular are where bacterial proliferate the most and absorb bad-smelling volatile substances which is why a polyester T-shirt tends to “smell” more than a cotton one.
How can we prevent this body odor?
In order to prevent the proliferation of bacteria in garments after they have been worn they must be washed as soon as possible at a temperature of at least 40°C in order to remove the micro-organisms. It can be very useful to use a sanitizing additive and last, for those who prefer natural remedies, sodium bicarbonate can be very useful when pre-treating and dabbing sweat stains.
Now let’s move on to another category of smells.
“Chemical smells”
When we buy a garment, we sometimes smell what could be referred to as a chemical smell, that is not caused by known natural causes (sweat, mold, fat, rancid…).
In fact, a considerable and unexpected quantity of chemical products are used to process fabric garments, and some of these are very strong-smelling. If manufacturing processes are not carried out as they should be and the products are not well-rinsed, they can remain on the fabric giving off unpleasant smells.
A sector where chemical products are used a great deal is denim.
Denim is a fabric with a rather intense, uniform color. In order to obtain special fashion effects such as 3D, stone washing, corrosion and bleaching… the garment must undergo a number of treatments that may involve the use of Cl2 ,chloride or K2MnO4 potassium permanganate which must be appropriately neutralized so that the fibers are not chemically damaged during processing.
If neutralizing is not done properly with the right quantities of products, the garment is very likely to have a “chemical” smell.
Another very particular example of chemical smells is the presence of a particular chemical substance that is widely used in the textile industry: formaldehyde.
It can be used to as a dye-fixing agent, as a component in some resins to create 3D effects on denim, to tan leather, or in wrinkle-resistant cotton. It is still widely present, however its use over the coming years will be restricted because it has been recently classified as a human carcinogen.
The presence of formaldehyde in a fabric can be perceived by smelling it, not because it is unpleasant but rather because of the fact that it is typically strong, and can even make your eyes water if there is a large quantity.
Fortunately the substance is rather volatile so its concentration tends to diminish if the textile is well aired.
How can chemical smells be removed?
Whatever chemical substance causes the smell, new garments should always be washed once or twice in the washing machine before they are worn, if the care label allows this. The operation removes all the soluble substances and salts in water, and as such the textile is “chemically” cleaner.
Any smells that remain even after washing indicate that something is wrong and it is important to find out why with the store owner and/or producer of the garment.
Can we measure smells?
There are two ways of measuring smells: one is to use our sense of smell on the textile and the other is sophisticated chemical tools which can determine the chemical nature of the substances that are released from the textile.
In the first case the fabric is placed in a closed room and after an appropriate interval of time a group of experts smell the room, assigning a point on the basis of a rising scale, such as:
In the case of measuring instruments, the textile is heated in a closed oven and whatever is released by the material is injected into a gas chromatographer with a headspace sampler, obtaining a chromatography of all the volatile substances that are released.
When the graph is read, it is sometimes possible to identify the presence of particular molecules that can be the source of the smell because of their intrinsic characteristics.
How can we prevent bad smells?
Special fabric treatments can definitely be applied to prevent the formation of smells, especially those caused by the proliferation of bacteria. Without mentioning any one brand in particular, it can be stated that silver ions, in products that are applied on the textile or directly incorporated in the fiber during production, can carry out an effective anti-bacterial action by interfering with the vital mechanisms of the bacteria.
Detergo Magazine – November 2015
