Sherry Washburn, Business Unit Manager – Supplies, at Videojet, looks at pigmented inks, their composition and how they play a crucial role in the food and beverage industry
For the majority of products manufactured worldwide, the inks used to code and mark the various barcodes and information necessary are dye-based. Interestingly, dye-based inks are transparent, even though they are colored, which means that the substrate they are printed onto plays a role in the overall appearance of the code content. Essentially, the ink itself will transmit or include the color of the background which, in the case of darker substrates, can cause issues with contrast. As you can imagine, applying a black ink to a black substrate will not produce the desired effect.
Manufacturers using dark substrates must therefore take a different approach with the inks they use to code and mark, and this is where pigmented inks offer considerable value. Pigmented inks effectively block out the color of the substrate, creating the contrast necessary to create clear, readable codes on dark surfaces. They are also particularly useful where transparent substrates are used as, once filled, the product within can affect the clarity of dye-based inks in some instances – particularly if that product is dark in color.
The common pigments used are TI02, which is white, and carbon black. Additional dyes can be added to color the ink, or a color pigment can be added to white to create more contrast if necessary. TI02 is the major pigment that’s used in inks, paints and coatings and can also be found in products such as sunscreen and correctional writing fluids, for example.
What are pigmented inks?
The major difference between pigmented and dye-based inks is of course that the former contains pigment. This pigment is not a soluble component in the ink – it is actually a solid particle that is suspended in the ink through chemical and mechanical methods. The pigment hides the background or substrate in a very similar way to paint on the wall or sunscreen you apply at the beach. Essentially, the pigment creates a physical barrier that hides or covers up the background so that the ink can be seen more clearly.
To achieve this effect, pigments are matched with a polymer that has a strong affinity to the pigment itself. The polymer has two functions in the ink. Firstly, it keeps the pigment suspended and secondly it adheres to the substrate. It is the binder that holds everything together. As we have made clear, the pigment masks the color of the substrate, but if the polymer did not act as a binder, the pigment would simply brush off. The polymer sticks to the substrate itself, which provides the adhesion necessary to create a code, in addition to rub, scratch and abrasion resistance.Pigmented inks provide high contrast across the widest range of substrate color variations. This significantly increases the versatility of the ink jet printer in a production environment, eliminating the expense of switching to different inks, and minimizing the need for ‘spare’ printers dedicated to specific substrate colors.
Pigmented inks in the food and beverage industry
In food packaging applications there are a wide range of products that would be far more challenging to code and mark were it not for pigmented inks. Mushrooms, for example, in the majority of cases are packaged using brown plastic containers, therefore whether the code is placed directly onto the brown substrate or onto a clear overwrap, the ink must be able to provide the contrast necessary for the code to be clear and readable. Products that use dark lids, too, are often coded with pigmented inks – a recent example of which is a peanut butter container that was tested for use in conjunction with pigmented inks at a specialist Videojet laboratory.
The beverage industry also relies on pigmented inks for clear, high contrast coding. Glass bottles used across a wide range of beverage products can be dark green, brown or amber in color, rendering dye-based inks redundant in the majority of cases. Videojet has recently worked with a major producer of soda drinks, where a yellow ink was recommended, in conjunction with a specialist CIJ printer, for their bottled offerings. This combination ensures that, regardless of which product is being run, the coding and marking system remains a constant and does not need to be changed.
Videojet inks are compliant with relevant regulations, which are closely monitored to ensure that any changes that may be necessary are made ahead of implementation deadlines. Regulations allow inks to be used on food packaging where the packaging provides a barrier between the ink and the food. In Switzerland, there is a Swiss Ordinance on Materials and Articles in contact with Food – legislation that is widely considered to be the benchmark – which places additional requirements on food packaging ink formulations. The European Printing Ink Association (EuPIA) publishes a list of recommended raw materials for use in food packaging inks. Many of Videojet’s inks meet these additional requirements specific to food packaging and the company works closely with its customers to select the appropriate ink for each application, especially where compliance is concerned.
The flexibility of pigmented inks
Pigmented inks offer enhanced flexibility, particularly for smaller manufacturers who may be running multiple colored substrates. Light blue, orange or yellow pigmented inks show up very well on most substrate colors - other than themselves of course. Light blue and yellow in particular are very popular, as they are not common colors used for primary packaging, therefore they are very flexible across clear substrates and dark glass bottles for example. This is an important consideration, as you cannot just change a pigmented ink – you would need a separate printer to print a different color, therefore this is a significant cost saving to manufacturers.
For pigmented inks, Videojet has developed the 1710 Continuous Inkjet (CIJ) Printer, which is very similar to all other Videojet 1000 line printers in the range. The key difference is that the bottom of the mixer tank is a conical shape, which prevents the pigments from settling on the bottom. The printer also agitates and stirs the ink on a prescribed basis so that the pigments are kept in suspension. This keeps the color of the ink consistent. As long as the printer is plugged in it will continue this process on schedule so that it is ready to go when needed – be it after a scheduled stop or for the following day’s production runs.
Regardless of the coding and marking requirements manufacturers face, what is important is to work closely in partnership with an expert provider of printing systems and inks. Through a thorough evaluation and testing process, the correct solutions and fluids can be selected based on individual requirements, leading to lower total cost of ownership and maximum availability of the printer when it is needed.