Besides the normal dirt, it is possible to identify some small stains of different colours on the garments. These kinds of stains cannot always be removed by normal washing with water or by dry-cleaning with solvents. For this reason, it is necessary to carry out a special SPOTTING treatment for each kind of stain
The stain removal is a complicated procedure full of risks: for avoiding ruining the garment in the attempt of cleaning it, it is necessary to understand the nature of the stains for using the corresponding spotting agents. You must become a real cleaning expert! This brief article will help you to learn more about the stains.
Here is a very simple method of classifying the stains by dividing them in two big categories:
Non-oily stains: are water-soluble and in the contact with the water, they are becoming darker as they are absorbing it. These are grass, fruit, coffee stains etc…
Fat stains: they are water-repellent, so not close to the water consistency. When coming in contact with the water, they are not changing colour because they tend to repel it. These stains include oil, glue, ink, etc…
A further, and even more specific classification of the stains can be made by considering their composition and nature:
Protein stains: also called enzymatic stains, composed of proteins. They can only be removed with specific enzymes (stains of blood, food, sauces, egg, grass, etc.).
Oxidizable stains: composed of dyes, tannins or metallic oxides (rust stains).
Sweat stains: composed by a non-greasy and a grease part, among these stains we can find also urine stains.
Liposoluble stains: stains that are not water-soluble and that can be removed with solvents (ball-point pen, glue, nail varnish, lipstick, etc.)
THE NON-OILY STAINS
These stains can be easily removed with water and surfactants. However, they contain substances that are difficult to remove, like pigments, tannins, sugar components and coloured components. For removing these elements, it is necessary to use a specific stain remover. The water-washing is able to remove most of the non-oily stains (excluding their pigmented part), something that the dry-cleaning cannot remove. As it is a complex stain, due to the various pigments, tannins or coloured components, we recommend a degreaser with a complete formula (attacking the stain on several fronts) with anionic and non-ionic surfactants, with sequestrants and enzymes for the destabilisation and degradation of the stain.
THE FAT STAINS
The fat stains are typically composed of triglycerides, synthetic and natural oils or fatty acids. They have a mainly a-polar structure that makes them water-repellent. Therefore, there must be used surfactants or degreasing solvents to remove them. They can be easily removed by dry-cleaning with solvents, and less by water-washing. For being able to eliminate the fat stains in a normal water-washing, it is necessary to make a pre-dethatching with a highly concentrated wide-spectrum treatment. You need to use a degreaser for the greasy part, but also possible related components. Furthermore, if the product contained solvents (even natural ones like Limonene) it would have more degreasing power even for the most stubborn stains.
THE PROTEIN STAINS
The protein stains, also called enzymatic stains, are composed of proteins. If denatured, (a process when the protein structure changes, caused by an external agent) they become insoluble. So, the proteins are irreversibly fixed to the fabric and the stain cannot be removed anymore. The proteins can be denatured in different ways: very acid pH, heat, chemical oxidation (sodium hypochlorite). To avoid this process, it is therefore better to start the spotting by removing the protein part. The other stain removers can then be used to remove the other components. For removing this stain, is recommended the use of a stain remover with a high concentration of surfactants and enzymes. The stain remover must contain moreover the enzyme Protease (called also subtilisin by its INCI name) for eliminating the protein stains. For a wider spectrum action, we are advising that the stain remover should also contain the enzyme Amylase as this particular enzyme works in synergy with the Protease, enhancing its efficiency.
THE BLOOD STAINS
The blood stains are of protein origin. The typical red colour is given by a protein (haemoglobin). This protein, if denatured, sticks irreversibly to the garment, fixing the red stain forever. To remove this stain, it is recommended the use of a spotting agent with a high concentration of surfactants and, above all, enzymes. The stain remover must contain moreover the enzyme Protease called also subtilisin by its INCI name) for eliminating the protein stains. After the degreaser treatment, it is recommended to use a powerful sanitiser or oxidiser (such as peracetic acid, hydrogen peroxide or sodium hypochlorite) for sanitising the fabric.
THE OXIDISABLE STAINS
The oxidisable stains have usually brilliant colours. The typical colouring of these stains’ changes between red and yellow. The coloured part comes usually from metal oxides like rust, or from coloured chemical photoactive compounds that absorb a specific visible light wave. The rust stains originate from the iron oxidation, that in contact with garment can transfer this oxide. The ferric oxide (Fe2O3) is dissolved only by very acid compounds and special substances. For removing the rust, it is necessary to use a specific stain remover. There are different types of rust removers on the market, mainly those based on acids or complex agents. Among the various types are those based on compounds of hydrofluoric acid or its salts. These are among the fastest and most effective substances for removing the stains of rust, however, compounds based on hydrofluoric acid or its salts are extremely toxic and dangerous and must be used with extreme caution and in complete safety. Other rust removers are based on phosphoric acid or oxalic acid. These stain removers are slightly slower in removing the stain (we are talking about tens of seconds difference) but much safer and not extremely toxic. Finally, for the oxidisable stains other than rust, the advice is to use a strong oxidant such as hydrogen peroxide or peracetic acid to oxidise and remove the stain.
THE WINE STAINS
They belong to the oxidisable stains category. This type of stain has the problem of the colouring remaining on the fabric, due to the tannins contained in the wine. The tannins were, in fact, dyes used in the past. The tannins are composed by different polyphenols produced by the plants. These substances are generated to avoid the attack of some predators and insects.
It is possible to proceed in two different ways:
– when there are many garments with very expanded stains, it is advisable to add a strong peroxide or hypochlorite-based oxidant directly to the wash.
– when dealing with localised stains, it can be used a specific stain remover that combines both surfactants and an oxidising part (usually peroxide-based)
THE SWEAT AND URINE STAINS
The sweat and urine stains are normally containing salts released by the human body, volatile and non-volatile organic components (e.g., urea, pheromones). The salt component can be easily removed with water, but the organic components (that are creating the yellow halo and odour) are difficult to be removed. The degradation of the pheromones and the fat part released during sweating creates the intense sweat odour and the yellow mark. For removing this kind of stains, there must be used properly balanced spotting agents, capable to remove both the saline and the organic part. We recommend stain removers that have a high concentration of anionic and non-ionic surfactants and that are also containing specific odour-degrading molecules. For a wider spectrum action, the spotting agent should also have an enzymatic part (especially Protease) to remove the protein residues from sweat or urine, which degrading could generate unpleasant odours.
THE FAT-SOLUBLE STAINS
The fat-soluble stains are stains that can be dissolved by a solvent. In this category of stains, we find stains of: ball-point pen, lipstick, wax, dye, etc. Fat-soluble stains are stains that are not soluble in water (therefore hydrophobic) and for this reason must be used a special stain remover that eliminates both the solvent-removable part and the pigmented part that could leave coloured halos. To remove the fat-soluble stains, is recommended the use of a solvent-based spotting agent (acetates, esters, ketones, glycols and etc.) and non-ionic surfactants. This stain remover must have a balanced solvent formula to remove the different fat-soluble stains.
THE AEROSOL STAIN REMOVERS
For a quick and efficient stain removal, can be used the spotting sprays. They have a very concentrated formula and a wide range of action. The aerosol stain removers, are talcum powderbased or similar, and they are mainly used in the restaurants. The dispensed powder will absorb the grease stain. Then the stain can be removed by brushing it. This type of spotting agent is mainly recommended for the grease or fat stains. It is not very efficient for some other type of stains. Another type of aerosol stain remover are the universal solvent stain removers, with high concentrations of solvents and nonionic surfactants for removing both fat stains and non-oily stains.
Finally, for safely removing the stains, there must be followed some specific steps and instructions in using the spotting agents. The right sequence in using the stain removers is crucial, as it is not existing only a simple “type” of stains, but they can be more complex, and they must be removed in steps, avoiding the fixation. This is why the stain removal is a job for the cleaning experts, that have the right experience to investigate the nature of the stain and use the right sequence to remove it! •
by
Alessandro Conedera – R & D Manager Tintolav Srl
(www.tintolav.com)
Detergo Magazine, Number 9, September 2022
