The core fundamentals of the inks you use

Ramu Ramanathan (RR): Should our industry deploy vegetable-based inks where suitable?
Akil Contractor (AC): Yes, that would be a welcome mindset. This is especially true for prints which are in contact with human skin tissue. Also, I feel, when inks are used on packaging or materials which are certified as biodegradable – it is at cross-purposes to use. For example, a PVC gloss ink to print on shopping bags which are manufactured from cotton and such natural fibres which are increasingly replacing plastic options.

RR: Are they less hazardous than mineral oil-based inks since they come from a renewable source?
AC: Vegetable, other natural and plant origin colourants have been deployed since time immemorial. They have been used to make dyes for dyeing fabrics. The colour chromaticity is in no way similar (or even close) to what is achieved by organic pigments used in printing inks as such for graphic and such applications of offset, gravure, flexo, and screen. But for guaranteed biodegradable applications  the composition of such inks have no other option but to utilise plant origin colourants.

RR: Is it commercially viable?
AC: Yes, it’s an idea whose time has come and the graph will always begin with a high cost  but just as  people are willing to pay more for organic foods and produce. Such safe colorants will be in demand, very soon. The information has to be disseminated about the advantages of such colorants in terms of health, safety and zero toxicity. Eventually all new technologies have to be viable in terms of cost and become more and more market-friendly due to the economies of scale. Someone has to make a beginning.

RR: When will we see mass produced inks?
AC: It will be a long time before the industry experts are able to chemically alter such plant-based colour cores that can substitute regular organic pigments used.  Presently, the organic pigments in use in inks certified as biodegradable have a chemical core and structure. It does not degrade along with the rest of the ink components. In other words, they are artificially synthetic organic compounds.

RR: Now to talk about your favourite topic: colorants. Where are colorants deployed currently?
AC: Currently, such colorants are used in the fabric and textile dyeing and on organic labelled goods. And so, the imprints on the packing and carry-bags are also certifiable as biodegradable. For example, a jute bag or bamboo origin bag is used which will bio-degrade. Having said that, the ink used would be the normal pigment based ink which defeats the purpose. Here a vegetable and plant origin colorant like charcoal for black, turmeric for yellows, alkali-treated turmeric for reds would be ideal as is being used.

RR: Are UV inks a better alternative to solvent-based inks?
AC: Thanks to the progress in ink technology, we have UV inks with the ability to instantly cure the ink on any surface or materials. Also, it permits the making for clear and sharp printing designs without any absorption into the surface /substrate with far better scratch abrasion and weather resistance and zero volatility (VOC).

RR: Can these eliminate the VOCs associated with solvent-based inks?
AC: In contrast, solvent inks or water or solvent-based inks require longer cure and drying time. They need heat energy which is expensive. Also, it can create printing problems and errors due to choking and premature drying on the screen. As well as extra costs for racking and storage before delivery. To top it all, all the coverage is lesser than UV since 25 to 40% of the ink evaporates (volatility is high) and yield of the ink is way lower than UV since it is a 100% solid ink.

RR: What is the lowest energy required for UV inks in terms of millijoules per sqcms?
AC: Clear UV varnishes can cure at 175 millijoules while pigmented inks cures at 300 millijoules sqcm . The UVA wavelength is the minimum required to start with some inks. I think it will efficiently cure when one starts from this dosage.

RR: Shifting the focus. What is the shelf life of scented inks?
AC: There are two types of scented inks. One is: aromatic. These are continuous smell inks which tend to diminish in smell. This is usually influenced by the substrate (thickness and absorption), relative humidity,  ambient temperature where the print is stored, circulation, and  distribution.

RR: Any way to prolong the shelf life?
AC: One can prolong the shelf life of such prints if immediately wrapped in a gas impermeable plastic. This can be removed at the point of perception. This is used for brochures, catalogues, wedding cards and short life print collaterals.

RR: Got it. What’s the second type of scented inks?
AC: The second type is the rub and smell /encapsulated inks. The life of such prints can range from six months to a few years  as long as the print results are  protected from pressure on the surface of the print which can prematurely puncture the  encapsulates. Also, it needs to be stored away from direct sunlight or heat sources. It is mainly used in activity books and medical evaluation. It is also used in print applications where the activity of the fragrance is assured over a long time-frame.

RR: Ice cream cartons and other freezer food containers require a lot of care because of the temperature fluctuations and how the ice cream carton is handled in a country like India. Which is the ideal ink for ice cream cartons according to you?
AC: If you are referring to the inks for printing the static design requirements, it’s usually food grade certified offset inks for cartons. Then there are UV cured offset inks. However for the containers it could be water-based flexo inks and for higher end UV flexo inks. For ice creams, solvent based options are least desired and highly avoidable.

RR: Does mineral-oil free ink serve the purpose of safe printing packaging? Or apart from ink, the chemical and substrate should also be VOC-free?
AC: During InkWeek hosted by PrintWeek from 21-25 March 2022, it was wonderful to hear that Siegwerk is ready with such inks. Also by substituting them with VOC-free diluents in offset inks, they will add to the safety in print packaging. Mineral oils do have health risks due to volatiles which add to air pollution and consequent toxic inhalations.

RR: What about the substrates deployed?
AC: Substrates, if filmic like PVC, then yes they are considered unsafe due to harmful exudations from such polymers. But normal paper substrates are safe for use.  The point is, chemicals in the inks are under constant watch and evaluation. That’s one of the reasons metallic driers have been substituted.

RR: When one replaces MetPet with a coated board how does one control high oil absorption value and lowest ink penetration?  Can you share how ink science works in this particular case?
AC: Well, coated boards are not as impervious as MetPet. Also one must bear in mind that the coating does not create as levelled a surface as a MetPet layer. There will be some level of absorption /penetration of the ink print.

RR: Such as?
AC: For instance, prime the coated board with a clear coat of the same ink system, modify the ink by adding fillers and additives which restrict  penetration, use UV inks which will be cured as soon as the print is laid so no opportunity for inks to penetrate.

RR: How does ink science work?
AC: The more sealed and primed the print surface is, the maximum ink will remain on the surface. A simple test is to put a drop of water on the substrate and watch how it behaves on metPET and how it responds on the coated board. For this one has to tilt the substrate and check the movement of the water droplet. On the metPET it will simply slide off and on the coated board you will observe penetration or a drag or other tell-tale signs which will indicate the behaviour
of a water-based ink option. The thing is, UV inks will probably have no penetration.

RR: Can you share some of the important developments in the direction of fully opaque white ink. For example, if a converter wants to print text with white ink on a four-colour brown background ...
AC: Let me try to share instances of how to maximise a lay down of white through different print processes. With flexo printing one can do so by using and opting for inks with high opacity, highest hiding power and yet low viscosity. This means using the highest number anilox possible for the font /design. This means, two hits where all other options have been exhausted.

RR: What about screen printing?
AC: In screen printing, it’s relatively easy because there is the easy option of using more coarser mesh or multiple screen strokes.

RR: Understood. And offset printing?
AC: It’s the most daunting task to obtain intense white due to the minimal gsm which can be deposited by the offset process. Once should not be too ambitious. However the UV offset can deliver a significantly higher opaque white layer as compared to oil-based sheetfed offset .

RR: I see. If one follows this, one can guarantee white on a four-colour brown?
AC: The point is, on a four-colour brown background specifically it would be helpful to first print a masking layer of a light grey colour on the brown. When this is done, then the white would appear brighter and more opaque. Maximising white begins with the choice of inks  -at times an ink can appear comparatively more opaque in the laboratory drawdown test but the print performance may not reflect this due to improper print  transfer properties.  

RR: One suggestion we received is: Ink-makers can make features such as high light fastness, chemical resistance and scuff resistance as standard features, rather than a separate grade of inks.
AC: All such features can be incorporated in a single ink normally with the use of additives and special raw materials. High lightfastness can be achieved by light fast pigments and UV absorbers, chemical resistance by use of chemical resistant resins and polymers to start with. Scuff can be added with wax additives. Ink makers have a super range of additives to incorporate all kinds of properties within an ink.

RR: Which are the new grades of security inks? And how can these inks help in the control of counterfeiting?
AC: There are several developments. Counterfeiting currency and counterfeiting a banker’s cheque or a  document or a luxury product all demand different avenues for security.

RR: How important is it to create a chain of training and ink mixing centres in all major towns of India where one can train people in the science of colour matching and ink mixing?
AC: A very difficult task indeed. Every ink manufacturer has been training their own employees for colour matching and ink mixing within their premises to create or cater to their customer’s requirements.

RR: But can this be done - and more importantly how should it be done?
AC: In order for this to be an educative training centre for all and sundry, it would need an institute or maybe more than one. Also ink themes need to be included in their  curriculum clearly laying down the minimum education qualifications to enroll for such a course. Ink is not a science or subject which can be open to the masses in the mass training centres. Perhaps one or two of the large ink manufacturers can fund such an activity in an institute or institutes. They can provide grants so that they can admit students and ensure a pool of skilled colour matching and ink mixing personnel for the benefit of the entire industry.

RR: Do-able?
AC: Yes, a good example is Vasai-based Grafica Flextronica (Textile printing specialist DCC Group has announced the acquisition of the Grafica range of printers from Vasai-based manufacturer of screen print equipment Grafica Flextronica) who conducted free screen printing education for the benefit of screen printing industry professionals.

Akil Contractor worked in the family-owned Rainbow Inks for 21 years before he embarked on his own enterprise Print Dynamic in 2002. Contractor’s aim has been to formulate and manufacture special application inks for textiles and security applications and technical ink formulation. Print Dynamic’s work has been recognised by the Limca Book of Records in 2008; and by the SPTF Foundation in the USA.