Maintain the color fidelity - light resistance and oxidation resistance test

(Keep Your True Colors: Lightfastness and Weatherability Testing)

After a product has been printed, if it is tested with a spectrophotometer and a densitometer, the results meet the requirements. The quality of the printed product should be very good and the customer is very satisfied. However, one day, the client dismissed the fact that the printed matter had faded. This may be due to the fact that ink printed on outdoor promotional materials fades under sunlight, or that some expensive printed materials are stored in fluorescent lamps. Discoloration or fading occurs below. No matter what the situation is, this phenomenon is something that everyone would not like to see. Just as Richard Harold said in the “Introduction to the Appearance Analysis of Printed Products,” the appearance of a product is a first impression, and it is one of the most intuitive factors to impress consumers. Therefore, the appearance of the product for a certain period of time with light resistance and oxidation resistance is of vital importance. Similarly, for outdoor posters, posters, billboards, and other printed matter, it is equally important to ensure the stability of the printing effect. To achieve long-lasting printing without losing color, the key is to realize the stability of printing inks and substrates under light and climate change conditions. These properties can be measured by various test tools. This article is a comprehensive comparison and introduction of various light resistance and oxidation resistance test tools. In the article, Julie Lucas of Q-Panel() introduced the various light resistance and oxidation resistance test tools available.
Lan Johnston of LLC() and Matt Greegan of Zeller+Gmelin() will introduce the relevant products of their respective companies.

When asked why Lan Johnston, the head of Inkware LLC, performed lightfastness and oxidation resistance tests on his products, Lan summed it up in one sentence. “That's to keep us safe in the future.”

When many people in the printing industry think that light and oxidation resistance testing is a useless task to save money and labor, Johnston and other experts have realized that this work is extremely critical. Johnston believes that the stability of printed matter is the first question that LLC should consider. If LLC printed products cannot maintain the high quality of printing, over time, customers lose trust in LLC, which is undoubtedly a great loss.

It is Inkware's important goal to realize the light resistance of products and the stability of weather resistance, because its products are mostly used on large outdoor billboards, signboards and flags. Inkware and VUTEK (), a manufacturer of inkjet inks, and an inkjet printer manufacturer, have been working together to develop and produce products suitable for outdoor printing.

However, as many industry experts have discovered, not only outdoor materials need to be tested, but bright indoor light and sunlight through the window panes also have a tremendous amount of damage. Therefore, the stability of the material is also very important for indoor products, especially for those works of art that have collection value.

In the printing industry, the annual losses caused by indoor light and various outdoor factors amount to hundreds of millions, including the fading of various inks, discoloration, and the fracture, peeling, delamination and oxidation of printed substrates. Bright indoor light, sunlight through glass windows, and direct sunlight are the main causes of these phenomena. Different wavelengths of light have different destructive properties. In general, long-wavelength ultraviolet light and visible light are the most destructive because they easily cause ink fading and discoloration. Short-wavelength UV radiation leads to the degradation of some of the more stable materials, such as paper and other substrates.

Lightfastness and corrosion resistance tests on materials are usually conducted during product development and quality control. Matt Creegan, product manager of offset printing at Zeller+Gmelin, said that the company's products are tested during the R&D phase and will be evaluated and improved in conjunction with the customer's use of the product. (Zeller+Gmelin is a professional manufacturer of UV-resistant inks. Its inks are mainly used for waterless offset printing, flexo printing and flat printing). The benefits of testing products are that they can better meet customer needs, such as customer requirements Outdoors can last for at least one year. The company will develop and produce products that truly have this performance through performance tests. With testing as a guarantee, it plays a positive role in establishing the company's reputation.

Greegan also said that since the stability of printed materials has become better and better in recent years, it has also brought another problem that it is difficult to find good red and yellow, especially yellow, in organic pigments. Stability, but also to ensure that the color, the company usually tests dozens of organic pigments to find a satisfactory.

Maintaining a balance between maintaining color accuracy and maintaining ink stability is also one of Inkware's goals. Johnston said that often Inkware has other options that can make the ink color more vivid, but the choice of these pigments may not guarantee the stability of the ink. So how to find a balance between color and stability and find a choice of color and stability is the only way to test it.

There are many kinds of methods for testing at present, but none of them are methods that apply to the world, and even the best solutions cannot be optimal for any kind of material and application. Therefore, the specific choice of how to test, must take into account their own work characteristics, time and funding constraints, and any kind of testing technology has its own advantages and disadvantages, when choosing to achieve as much as possible.

Usually the most accurate test method is to place the product under test directly under sunlight. This real-time, outdoor testing is best done in Florida and Arizona, where extreme weather conditions can accelerate material degradation. It is well known that the climate in Florida is characterized by high temperatures, high humidity, and high rainfall, while Arizona is highly humid, highly UV-radiated and extremely dry. In fact, these areas have become the benchmarks for global climate testing. This is precisely because of these characteristics, manufacturers have chosen Florida and Arizona for outdoor testing of products.

Zeller+Gmelin and Imkware have set up their own test sites in some extreme climate regions and have obtained a large number of test data. Zeller+Gmelin's outdoor test sites are located in Virginia, Texas, and California. Inkware uses its advantage in Nevada to test directly in the area. Inkware has accumulated outdoor test data since its establishment seven years ago. According to Johnston, Inkware has been testing for more than six and a half years and its accumulated data is quite valuable.

Real-time, outdoor testing is accurate, and costs are low, but at the same time there is an obvious drawback - too time-consuming. When a manufacturer wants to launch a new product, it is impossible for him to wait a year or even years to check the durability of the product. Therefore, conducting outdoor tests is usually for projects that are not limited by time.

The opposite of outdoor testing is accelerated laboratory testing, and many manufacturers have successfully applied this method. This accelerated test simulates various outdoor environments and amplifies and alternates them to give a simulated result in a shorter time. With the recent development of new technologies, this accelerated environmental simulation test has also been continuously improved.

There are many devices currently used for this type of testing. They can simulate sunlight, fog and other destructive ways to be different, because the principles have similarities and differences, so before choosing a device, we must first understand the respective principles, to measure and Compare to choose the most appropriate solution.

Around the carbon rod may be the oldest light resistance test device, probably starting in 1918. In this device, the test object is erected vertically in the middle of a pair of carbon rods, and the carbon rods burn to generate light. Because this device lacks short-wavelength ultraviolet light, the test results are too simple and are rarely used today.

Luminescent charcoal is an improvement on the surrounding carbon rods. It introduced a light resistance test in 1930. It differs from the surrounding carbon rods in that it is itself a light source and does not need to rely on combustion to emit light. Luminescent carbon emits ultra-violet light with very short wavelengths, but luminescent carbon creates an environment that is too sharp and unnatural, and test results are not representative enough.

As most researchers realize, although the carbon environment can provide a lot of useful data, people can already find more accurate methods, and the test equipment developed by the relevant manufacturers allows people to carry out their own tests.

The equipment provided by Xenon can more accurately reproduce the light in the entire spectrum. Xenon light can not only emit ultraviolet light, visible light and infrared light, but also has the same light emitting principle as the sun, so it can provide more accurate data. Xenon also offers a sprinkler that simulates a wet environment. The Xenon device can test the light resistance of the product very well because many products fade or discolor after being exposed to ultraviolet and visible light at the work wavelength.

At present, both Inkware and Ieller+Gmelin have used Xenon devices and used outdoor tests to check the stability of the products. At the same time, in order to ensure the accuracy of the Xenon test results, the two companies compared the Xenon test data with the outdoor test data, and it turns out that the two are extremely close. It can be seen that Xenon test results are trustworthy.

The downside of the Xenon test set is that many Xenon devices are more expensive than other test devices of the same type or outdoors.

The fluorescent UV/coagulation tester uses a light source similar to the white light of daily lighting, but it can produce ultraviolet light instead of visible light or infrared light. This allows the test object to be tested under short wavelength ultraviolet light. Because short-wavelength ultraviolet light is the largest part of the damage of the durable medium in the entire solar spectrum. So this part of the test is essential.

The UV test device can also simulate fog through an condensing device. This creates a more realistic simulation environment because outdoor studies show that condensation is greater than the humidity generated by rain. In addition, some UV test devices are equipped with water spray devices to simulate the phenomenon of thermal shock. This climate is quite destructive to some materials.

Inware used UV bulbs for a lot of testing. At first, Inware was tested from a scientific point of view because ultraviolet radiation was the easiest cause of fading. Therefore, Inware initially used only high-intensity ultraviolet light to prove that not only high-intensity ultraviolet light has lethality, but also low-intensity ultraviolet light is irradiated for a long time. Extremely destructive. Although the accelerated test method can provide a lot of useful data, it is not absolute. There are some facts that must be tested for a long time. Therefore, Inware will use the Q-Sun test device to conduct outdoor tests.

Johnston said Inware will still use UV light bulbs for testing. If the company needs to give a quick assessment of a material, it will first consider this UV test, although this is a very extreme test, but it is indeed quite fast. After the material is able to withstand this UV attack, it will be put in the Q-Sun test again, from which to choose the best reproduction.

The UV test device is easier to operate and the price is lower than the first two test devices. Its main drawback is that the UV light bulb cannot produce visible light for every outside line, and it cannot test the ability of the material to resist visible light and infrared light. This property is an important criterion for assessing the material's resistance to fading and discoloration.

The above is the introduction of several major test devices. From the introduction we can see their respective advantages and disadvantages, as well as their own suitable test items. In fact, if you want to test well, the best method is to try more. The more you test, the more times you have, the better you will be able to understand your product's performance, strengths and weaknesses, and you will be better able to start improving. Both Zeller+Gmelin and Inware have taken comprehensive tests including outdoor and accelerated experimental testing. According to Johnston, Inware had encountered this situation. A product performed well in accelerating experimental tests, but soon it began to degrade outdoors. Therefore, only through comprehensive testing, can we have confidence in ensuring the quality of our products. Another advantage of choosing multiple test methods is that they can be compared