Last time we spoke, we told you all about triple 4 and ways to achieve it. You might remember the story about the cocktail: a combination of products that you need to keep your white fabrics from yellowing. But how do you get to the right recipe? The answer is simple: you test it. In this article, we will show you how it is done in our Tanatex Lab. In this fully equipped laboratory, we test the fabrics of our customers for their resistance to, among other things, NOx and sunlight. So that in the end, we know exactly what it takes to keep them white. Come in and we will show you around!
About the process
This is how it works. When a customer calls for our assistance, we ask him to send us samples of the fabric he works with. We then expose his samples to all factors that cause yellowing and find out their level of resistance. In a second stage, we add one of our anti-yellowing products to the samples and compare the results. We do this until we have found the ideal amount of each product, so we can create a tailor-made recipe for each single customer.
In our lab, we use five parameters*:
4. Phenolic yellowing (BHT)
5. Optical whiteness
*You can find a more detailed explanation on the yellowing factors in our white paper The Ultimate Guide to Extreme Whiteness.
Before we zoom into the yellowing factors, first we check if the sample needs cleaning. Many fabrics, especially polyamide elastane blends, contain oils that turn yellow when the fabric is exposed to high temperatures. This is why we carefully test the composition of the fabric. If it does contain a lot of oil, we wash the fabric with our washing agent DIADAVIN® DSP. If it does not, pre-treating will not be necessary.
In our first yellowing test, we expose the samples to NOx gasses. This is done in a bell jar, where a constant flow of NOx is released into the air. We leave some of the samples inside the bell jar and compare them to samples that were kept outside of it. This process is repeated until we know the exact resistance level of the fabric. Later, we add a combination of SPANSCOUR SPARK and TANASSIST® PROSET to the sample, a finish that protects the fabrics against NOx and BHT. We compare the results and find out how much of the products is needed to preserve the whiteness of the fabric.
In the second stage, we test for light fastness. During a couple hours, the samples are put under a Xenon lamp. This lamp simulates the radiation of the sun, but in a way that the testing hours are comparable to a much longer period of time in real life. This way, we are able to test the influence of months of sunlight in a much shorter time frame. Apart from the regular samples, we add a blue standard that acts as a reference. After a couple of hours, we start to check whether the white sample shows signs of yellowing. We do so until the whiteness of the sample ‘breaks’ and starts to change colour. At this breaking point, we compare the yellowing degree of the sample to the colour difference of the blue reference. Based on this comparison, we are able to draw conclusions on the light resistance of the fabric. At this stage, we are able to tell how much of our product BLANKOPHOR should be added to reach the requested parameters.
During the production process, many fabrics are moulded so they take on a certain shape. Think about the folds in the collar of a shirt or the cubs of a bra. This moulding is done under high temperatures, and endangers the hue of the fabric. This is why we mould some of the samples ourselves and see what happens. Thereafter, we apply Spanscour Spark to some new samples. This product arms the fabric against high temperatures by providing it with a thin layer. Just like in the other stages, we repeat the process and report on the differences.
4. Phenolic yellowing
Butylated Hydroxytoluene (BHT) molecules in combination with NOx cause phenolic yellowing, a chemical reaction that makes fabrics look yellow. They are often added to plastics, meaning they are everywhere. In our lab, we therefore always test for the BHT sensitivity of the fabric. We wrap the samples in BHT impregnated paper, place a five kilo weight on top of the package and put it in a stove for sixteen hours. We add several doses of our anti-yellowing product TANASSIST® PROSET to a couple of them, so we can compare the results. Based on the outcome, we decide on the amount of TANASSIST® PROSET that should be added to protect the hue of the fabric.
5. Optical whiteness
As the market calls for very specific shades of whiteness, many manufacturers use brighteners to create a so-called optical whiteness effect. This is why, in this last stage, we check for the quality of this optical whiteness in the samples. We do so by testing the shade in different sorts of lighting, such as northern daylight. This daylight comes through our glass roof, that was built especially for this purpose. We also use a spectrophotometer which objectively measures the shade and the whiteness of the fabric. To obtain the best possible degree of whiteness, we add Blankophor, a product that whitens the fabric and strengthens the hue. As optical whiteness products are not chlorine proof, we use BLANKOPHOR® CLE liq. for swimwear and beach towels, and BLANKOPHOR® PAS liq. for other fabrics.
As soon as we have done all the tests, we document on the results in a report. Here, we give our advice on which combination of products to use and how to get the best out of them. Our customers get a good picture of the traits of their fabric and the way they can fight the yellowing process. This means that in the future, they will be better capable of protecting their products against all the external influences they cannot control. In turn, their customers receive higher quality, which will strengthen both the customer relationship and the loyalty of the end-user.
That was a lot of information to process, we reckon. But if you want to tackle all of the factors that influence the whiteness of your fabrics, you need to have a tailored recipe. Do you want to discover yours? Just say the word!
Just say the word!
That was a lot of information to process, we reckon. But if you want to tackle all of the factors that influance the whiteness of your fabrics, you need to have a tailored recipe. Do you want to discover yours? Just say the word!