The development of an ink requires many aspects to be taken into account. The demands on a "simple" ink have increased enormously. Historically, it has developed from a writing and drawing ink of antiquity into a multifaceted product with a wide variety of requirements in the technical and creative fields. In this context, not only the further development of various technologies plays a role, but also ecological and economic aspects. Basically, a development consists of three stages:
In the first stage, the exact purpose of the ink, the application process and all the requirements that the ink must meet after application must be recorded.
In the second stage, extensive and repetitive laboratory tests must be carried out to develop a suitable base that meets all the requirements that were collected in advance in the test device.
In the last step, fine-tuning takes place. Here, mainly colour adjustments, final adjustments to the printing system, the development of a manufacturing process as well as the definition of parameters for ensuring consistent quality are required.
The requirement and specification of each ink is unique and optimally matched to the corresponding system.
We generally distinguish between two large areas in the types of inks we develop. On the one hand, the technical inks, such as inks for poster printing, for MHD indications, marking of styrofoam/polystyrene or for markings with regard to quality assurance within production lines, cover a large area. Here, great attention is paid to drying speeds, automated optical readability, adhesion, substrate wetting and area-wide printing, to name just a few examples. After all, a special application requires not only chemical but also technical understanding. Added to this are the most diverse requirements, taking into account physical parameters and the printing technology itself. These technical inks are mostly inkjet inks.
On the other hand, there are ink developments in the creative and hobby sector. For this area, the development of colour concepts and the physical properties are essential with regard to the requirements. Here, the ink formulation must be finely tuned to the application possibilities, such as for use with a brush or in a fountain pen, and must harmonise with the substrate in the best possible way. Particular attention is paid to drying times, water resistance, feathering, bleed-through and especially light fastness. Similar to industrial/technical inks, the same applies to creative inks: For a special application, both chemical and artistic technical understanding are required.
Basically, our inks can be divided into two types based on their composition:
Water or solvent/solvent. Here, not only the properties of the inks play a role, such as wetting, adhesion of the substrate, physical parameters, etc., but also the printing system itself. Not every ink can be used in every system and is therefore usually an individual solution. Furthermore, a suitable colouring agent must be selected. In the conventional sense, a distinction is made here mainly between dye and pigment.
Dyes are chemical compounds that have the property of colouring other materials and are soluble in the medium itself. Due to their excellent solubility, their incorporation is usually uncomplicated. However, dyes have the disadvantage that they are not particularly lightfast and thus not durable enough for some applications.
Pigments, on the other hand, are finely ground particles that are insoluble in the application medium. In contrast to dyes, pigments require complex pre-treatment to bring them homogeneously into solution.
Pigment or particle stabilisation is realised with the help of a wide variety of additives. When using surface-active substances, additives, special care must be taken to ensure that all the components to be used harmonise with each other. Otherwise, agglomeration (flocculation) of the particles can occur with these inks, among others, and thus the finest ink conductors can become clogged, regardless of whether it is a print head or a writing instrument.
In addition, the physical properties mentioned above, the adhesion to the substrate and other individual requirements are adjusted with the help of the additives.
If all the aspects mentioned are put together, a "simple" ink is not just a colouring liquid, but rather a very complex system that is precisely tailored to a specific application. It is precisely this aspect that makes ink development so challenging. Only the smallest change can determine the success or failure of an ink in the corresponding system. After finalising an ink formulation on a laboratory scale, further development work may be required to transfer it to a suitable manufacturing process, carry out long-term tests and establish a quality management system.