Fabric stains
Who does not know it? Yellow stains on the T-shirt from deodorant and sweat, grease stains on summer clothes from sunscreen, make-up marks on the shirt collar – fabric stains are a vexed topic.
This article will give an overview of the different types of textiles and detergents. In order to understand fabric stains and their removal, one must first examine the properties of the textiles and types of dirt in more detail, in order to then develop appropriate solutions for removal of fabric stains resulting from cosmetics.
Textile types
The fabrics from which our clothes are made are composed of fibres that can be of natural or chemical origin.
In the case of natural fibres, a distinction is made between animal fibres (e.g., wool, cashmere, silk), which are chemically composed of proteins, and plant fibres (e.g., cotton, linen, hemp), which are composed of cellulose.
Man-made fibres are classified in natural and synthetic. Natural man-made fibres also consist of cellulose. They reobtained from wood fibres by dissolving them and then pressing them through nozzles to obtain a long fibre (e.g., viscose, modal, lyocell). Synthetic man-made fibres are made from products of petroleum.
It is common to make textiles from blended fibres. Different fibres are used (e.g., 60 % cotton and 40 % polyester) with the aim of improving the properties of the textiles.
To evaluate fabric stains, the properties of the fibres are of particular importance. Under the microscope, one can see that the synthetic fibres are significantly thinner than the natural fibres and have a smooth structure. The natural fibres are thicker and have a rough surface. Both synthetic and natural fibres can have a high water absorption capacity. The difference here, however, is that with natural fibres the water is stored within the fibres. In the case of synthetic fibres, the water is stored more in the spaces between the fibres, which gives these fabrics the property of drying more quickly. The polarity of the fibres is also important. According to Dr. Strauß’ “Stain Removal Workshop” (2018), chemical fibres have a rather non-polar character and are thus lipophilic (grease-loving and water-repellent).
Overview: Types of detergents
Detergents are usually composed of five different ingredients: Surfactants, softeners, enzymes, bleaching agents and other auxiliary substances.
Surfactants are substances with a fat-loving (non-polar tail) and a water-loving side (polar head group). This structure gives them a washing-active property. They attach themselves to the particles, detach them from the fibre and disperse them in the form of micelles in the washing liquid. By enclosing them, they prevent them from re-accumulating. Since different types of dirt can adhere to clothing and lead to textile staining, a mixture of different surfactants is used. These are anionic surfactants, which have a negatively charged head group, and non-ionic surfactants, where the head group is uncharged but still polar.
Softeners ensure that calcium and magnesium ions of the “hard water” are bound. This counteracts a build-up in the machine and in the pipes.
Enzymes are proteins that control and catalyse biochemical reactions. They can specifically attach themselves to substances and cleave them. The detergent industry has taken advantage of this property and proteases (to break down protein), lipases (to break down fat) and amylases (to break down carbohydrates) are used to counteract the widest possible spectrum of fabric stains. Cellulases (cleavage of cellulose) are used to smooth the corresponding fibres.
Bleaching agents are contained in heavy-duty detergents and prewash sprays and should only be used for white laundry, if possible.
Auxiliary agents may include optical brighteners, fragrances, inhibitors and setting agents.
Depending on the type of detergent, the ingredients are combined and coordinated with each other:
Heavy-duty detergents: “Universal detergents” in powder form contain surfactants, enzymes and softeners as well as bleaching agents and optical brighteners and are therefore mainly suitable for white or light-coloured laundry. Liquid heavy-duty detergents do not contain bleach and are therefore gentler on coloured laundry, but they do contain preservatives that are detrimental to both the environment and people with sensitive skin.
Detergents for coloured and delicate fabrics: These do not contain bleach or optical brighteners and are therefore suitable for coloured and dark clothing. They may contain colour transfer inhibitors as an additive. They prevent colour and dirt particles that have been removed from other garments from reattaching to the fibres. This prevents the textile from being stained again.
Wool detergents: For natural animal fibres such as wool and silk, use detergents that do not contain enzymes. Proteases can damage the fibres, which are made up of structural proteins.
Special detergents: e.g., for sensitive skin (no preservatives and strong fragrances), functional detergents for sportswear (odour-neutralising additives).
Compact detergents: Powder detergents that do not contain sodium sulphate, which is used to improve the pourability of the detergent. This makes them less harmful to the environment than normal heavy-duty detergents.
Fabric softener: Does not belong to the detergents, but should be explained for the sake of completeness. It contains only cationic surfactants. These do not have a washing-active function, but lay on the negatively charged fibres after washing due to their partial positive charge. Roughened fibres are smoothed. The smoothed fabric structure improves the comfort and appearance of the garment.
The smoothed fabric structure improves the comfort and appearance of the garment, and the laundry does not become stiff during drying. However, it is not suitable for all textiles and is often overdosed, which is harmful to the environment.
Bile soap: The washing power of bile soap is based on the emulsifying effect of the salts of the bile acid it contains. They reduce the surface tension of the water (similar to surfactants) and thus rearrange and remove the dirt particles. Bile soap hardly contains any enzymes that are active in washing.
Fabric stains due to dyed cosmetics/deodorants/sunscreens/sweat
For fabric stains, it is important to understand what type of dirt is involved or how the stains are chemically composed. A distinction is made between water-soluble substances (food residues, (body) sweat), starch- and sugar-containing stains (sauces, syrup, fruit juices), protein-containing stains (blood, cocoa, (underarm) sweat) and fat-containing substances (oils, skin grease, creams and lotions). There are also dyes or tannin-containing stains (plant-based: fruit, wine, coffee, grass) and pigment dirt (make-up, dust, soot).
Water-soluble and grease-containing stains, pigments and protein-containing stains are particularly important here, as we are talking about fabric stains caused by cosmetics and sweat.
How the stains settle on and into the fibres depends on both mechanical and chemical interactions. Synthetic fibres have a smaller specific surface due to their smooth surface and thus offer less surface for small dirt particles to adhere to the fibre and in the spaces between the fibres. (Pigment) dirt can therefore be removed more easily from synthetic fibres than from natural fibres. Water-containing stains can penetrate natural fibres, whereas in synthetic fibres they are more likely to adhere to the fibres. So even with this type of fabric stains, synthetic fibres are usually easier to clean than natural fibres. Greasy stains are an exception here. Due to the aforementioned lipophilic property of synthetic fibres, fats adhere more strongly to them than to polar natural fibres and are thus more difficult to remove.
Possible solutions by pre-treatment and washing
Greasy stains can get on clothes through various cosmetic products such as sunscreen, lotions, and oils. Pre-treatment with bile soap or dishwashing detergent can be used to remove stains. Common detergents contain anionic and non-ionic surfactants, dishwashing detergents additionally contain amphoteric surfactants. They also contain lipases, i.e., fat-splitting enzymes. Due to its composition and usually higher concentration than in detergents, it has an effective grease dissolving effect. For particularly stubborn grease stains, petroleum ether is a good choice. It dissolves not only oil stains but also wax and paint stains. (Safety instructions must be observed! Use only if conventional agents do not work, as it is highly polluting and can irritate the respiratory tract).
Coloured (pigmented) cosmetics may be pure pigments (eye shadow, rouge, powder) or pigments bound to fat (tinted creams, make-up, lipstick). For this reason, special pigment solvents are usually surfactant combinations with fat-splitting enzymes. A pre-treatment with concentrated dishwashing detergent should also be able to dissolve the pigment particles from the fibres by means of surfactants and enzymes.
Sweat stains, which occur e.g., on the back and thus leave stains on T-shirts, consist mainly of water, and contain various ions, amino acids (proteins) and urea (water-soluble substance). Sweat from the eccrine sweat glands, which are distributed over the entire surface of the body, is usually clear and odourless and could be removed from textiles by a simple wash cycle with heavy-duty, colour or mild detergent, as these also contain protein-splitting enzymes.
Sweat from the apocrine sweat glands of the body, which are located in the armpit and genital area, has a different structure and is therefore more difficult to remove. The milky secretion mainly contains proteins and lipids. Intensive pre-treatment with bile soap or special stain removers for protein and dishwashing detergent is recommended here. Stain removers against protein contain proteases that can specifically break down proteins. Dishwashing detergents, as already mentioned, are effective against the lipids of sweat through three types of surfactants and lipases.
Fabric stains caused by deodorants are probably among the most stubborn. The yellowish stains on white clothes or white stains on dark clothes are caused by the reaction of sweat and sebum with the aluminium compounds in some deodorants. You can try to remove these stains by pretreating them with bile soap. For older stains, you may have to resort to chlorine bleach (only for white clothing). These stains are really difficult to remove, so it is important to prevent these fabric stains in advance. Since the yellowing is only caused by the washing cycle, pre-treatment should be carried out in any case. It is also advisable to apply the deodorant sparingly and allow it to dry so that no residue sticks to the clothing.
Instructions for use on the packaging
In our opinion, coloured cosmetics, deodorants and sun protection products should always be labelled “Product may cause staining of textiles“. Especially when dyes are used, as well as natural dyes, this information should not be missing. In the case of deodorants and sunscreens, the following could be added: “Product may cause staining of textiles, which may also lead to permanent stains“.
Cosmacon can work with the Sächsisches Textilforschungsinstitut e.V. (STFI) (http://www.stfi.de) to develop a washing performance for the product in question or also offer tests for the potential of textile staining.
This gives the distributor of cosmetics a certain degree of security in dealing with future complaints on this subject. After all, the probability of complaints is very high when these types of cosmetics are offered. Possibilities should be worked out in advance to be able to give the customer a good answer.
NOTE:
It has been mentioned several times that dishwashing detergents can be used to remove fabric stains. However, it is important to know that although shampoos or shower gels also have a washing effect, they should never be used to remove or pre-treat stains!
Shampoos and shower gels that promise easy combing or a pleasant skin feeling often contain a synthetic plastic called “polyquaternitum-7”. This substance works in a similar way to the cationic surfactants in fabric softener, laying on the fibres and thus smoothing them. It lays on the negatively charged skin and hair and is supposed to improve the skin feeling and the static of the hair. The problem: when textiles come into contact with shower gel and are subsequently washed, the positively charged particles act like magnets, binding dirt and colour pigments from other textiles to them. This means that the washing causes fabric stains.
Tip: Acidic household remedies such as citric acid and vinegar are tanning agents and can be used for coffee, tea and fruit stains, but are of little use for fabric stains due to cosmetics.
Tip: Always use cold water first to rinse. Warm/hot water causes the fibres to swell and the dirt particles get deeper into the fabric.
Tip: Fresh fabric stains are easier to remove. Pre-treatment is especially important for deodorant, fruit and blood stains.
Literature
Fachwissen Professionelle Textilpflege 2018; Rudolf Gämperle, Heike Gläßer, Christian Himmelsbach, Meinrad Himmelsbach, Werner Ring, Michaela Rößler, Sabine Ruchhöft; Europa Lehrmittel