We talk a lot about the inks we manufacture and how proud we are that our products deliver excellent quality for our customers, by ensuring every ink that comes out of our factory meets our standards for 'Needham Quality'. But, how exactly do we achieve this? What checks do we put our products through to guarantee their quality? Keep reading to find out.
With over 59 years of ink development and manufacturing experience, Needham Ink Technologies provides a broad range of inks to a distributor network in over 73 countries. Over the decades we have maintained a successful track record of continuous growth and innovation. As a family-led business, our key focus is to create valuable, long-lasting relationships with our clients, and provide you with the means to grow your business.
To ensure this, our top priority is to ensure the quality of the products we manufacture. Each of our inks is rigorously tested to ensure the highest quality product leaves our factory doors every time. Our team of chemists, based in our research labs at Whitchurch and Newquay (UK) ensure that each ink product that we produce can deliver excellent colour accuracy and reliability for our customers.
We have a Quality Assurance process in place which checks six key properties of the ink products we make, and if any of them are not absolutely perfect, our ink makers will continue working until it is. So, what are we looking for?
One of the first things we check is the viscosity of our inks. Viscosity is essentially the thickness of ink or its resistance to flow. If ink has low viscosity, it flows more easily and will have a more water-like appearance on a surface. Ink with a high viscosity will appear more sticky and gelatinous, and will not move as easily. The desired viscosity of an ink product will depend on its intended use and the printing process that it has been manufactured for, as well as the surface it is going to be printed on. When we measure viscosity, the ink is placed into a chamber (pictured below) to be warmed to the correct temperature. This is important as viscosity changes with temperature and we need to ensure we measure it at the same temperature every time. Viscosity is measured in units called Centipoise (cP).
Inside particles of a liquid, molecules move in every direction. Except for the surface of the ink particles, where intermolecular forces move from above towards the inside of the ink. This movement produces surface tension. Simply put, the surface tension of ink determines the shape of a droplet and also how that droplet interacts with the surface it is printed onto. We use a Surface Tensiometer to measure the dynamic surface tension of our inks. Surface Tension is measured in units called Dynes.
The colour of ink is obviously one of the most important elements, with different printing applications requiring different colours. When a customer specifies a particular colour, we test the ink to ensure it is correct. All of the colours we can perceive are produced by the mixing of certain basic colours. We use a Spectrometer to measure the colour of the ink. Every colour can be mathematically described using three numbers in the CIELAB colour space. By measuring these numbers, usually referred to as L*a*b*, we can ensure exactly what colour of ink we have produced and thereby ensure each batch is the same as the last one.
Another test that we also do is a 'drawdown' test. This allows for the ink to be checked for any impurities and contaminants and allows a naked eye check of the colour and vibrancy of the ink. This process involves pressing a small quantity of ink onto a flat piece of paper (usually vinyl).
The specific gravity of ink is a measure of the density of the ink. But, why do we need to know this? Specific gravity is important to measure as it allows us to be certain we have mixed the correct chemicals together, in the correct ratios, and produced the correct ink. Specific gravity is measured by placing a device called a 'hydrometer' into the ink. Measurement is taken from the hydrometer which, simply put, indicates how far the device has been allowed to fall through the ink.
pH is a measure of the acidity or alkalinity of water-based ink. Inks contain billions of extremely small pigment particles which have to be suspended in water t prevent them all from falling to the bottom of the bottle. The stability of those particles is dependent on the pH of the solution they are in. Too high or too low and the dispersion may break down causing the pigment particles to form sediment and ultimately the ink to lose its colour. The pH of ink also determines how that ink will interact with the material it is printing onto. The pH of ink is usually measured by using a pH meter.
Conductivity is the ability of a liquid to transmit or conduct an electrical charge. Just as a wire conducts electricity so can a liquid. But in a liquid, the current is carried not by electrons but ions, which move through the liquid taking electrical charges with them. While electrical resistance is measured in “Ohms”, conductivity (it's opposite) is measured in “Seimens per metre”. Conductivity is important in continuous inkjet inks because, in the printer, the droplets of ink have to be capable of carrying electrical charges. If they were not conducive the printer would not function. Measurement of conductivity is taken by placing electrodes into a sample of ink and taking a reading from the conductivity meter.
We have put together a video of our QC processes:
So, there we have it. That's the process our Quality Control team uses to put every ink product through its paces and to ensure they always meet our standards for the 'Needham Quality'. Our aim is to always provide the right solution for our customers, and this means ensuring the products we manufacture are right first time, every time. If you have an idea of what you need, why not get a quote from our team:
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