WHAT IS INK?
WHAT IS INK
Ink is a primary tool used to convey a message and give decoration to a substrate. For this to occur an ink must have specific properties if it is to perform properly. It is of no value if it will not transfer to the substrate or adhere in a proper manor. Ink makers must cater for a wide variety of requirements and retain the ability to be flexible in what they manufacture. The contents of any ink are dependent on the conditions under which the products are to be printed and the end use requirements of the printed piece. At its basic definition ink is a combination of components mixed together to form a fluid capable of printing from a printing press.
Colorant/pigment is probably the most important item in ink because it conveys the visual identity of an ink. It is also the major cost in an ink far exceeding all other components. Pigments give color to a substrate by either remaining on the surface or having a tendency to fill in voids on the substrate. An example would be a coated sheet versus an uncoated sheet where the ink will remain on the surface of the coated sheet and fill the voids of an uncoated sheet. Colorant/Pigment is provided to the ink manufacturer in two forms, a dry powder, or in a paste form where the pigment has been wetted with a varnish/vehicle. Most are synthetic materials produced from petroleum chemicals, which are inorganic, while others are organic and formed by nature in mineral or vegetable form.
Pigments are grouped according to their chemical composition. Usually that means color. Each is identified by name and a color index number; example Lithol Rubine - Pigment Red 57:1. 57 giving its identification number and the 1 indicates that it contains a percentage of Barium compound.
The basic groups are:
1.Yellow 3. Red 5. Blue 7. Black 9. Pearlescent
2. Orange 4. Green 6. Violet 8. White 10. Metallic 11. Fluorescent
Each group contains various shades of hue. Example, yellow will vary from greenish yellow to bright warm yellow. Thus, you can have many different shades of each pigment to achievean optimum color match. Within each group of pigments there are several grades of pigment with a single color index reference. They each may differ in relative density, oil absorption and opacity. They each may have special properties such as light fastness and water resistance. Each can be modified to meet specific
Vehicle/Varnish is to which a pigment is suspended and allows for transfer of color to a substrate. Varnishes are a combination of different types of resins. Resins, by themselves, are of two basics types, natural and synthetic. Most resins today are synthetic and are made by polymerization involving condensation or addition reactions between relatively small molecules. Usually a vehicle/varnish is a combination of different varnishes, each designed to give ink a specific property or characteristic.
Just as in the case of pigments, there are various types of vehicles/varnishes. Vehicles/Varnishes are used to give ink body, a gel varnish for stiffness, varnishes used to give ink good flow properties, a lubrication varnish, varnishes for a hard dry ink, varnishes for quick setting inks and varnishes that achieve a high or dull gloss effect. Vehicle/Varnish in general is used to achieve three specific functions:
1. Used to wet the pigment. Allow the pigment to be fully dispersed in an ink formulation and to give an over all stability to the finished product.
2. Incorporate printability into the system. Allow an ink to transfer through the roller train of the printing press and onto the substrate. Without the varnish an ink would not transfer
3. Bind the pigment on to the printed surface. Vehicle/Varnish gives the ink its binding and adhesion properties. Various types of varnishes are used to harden the ink and give an ink quick setting qualities.
The formulation of a varnish is one of the most critical steps in ink making. Varnish has so many key properties and characteristics, that a combination of various types can be the difference between a good performing ink and a bad performing ink. Extreme amounts of R&D takes place when formulating varnishes as a vehicle system to wet pigments.
The third component of ink is what we call additives. Additives are very specialized components that give ink special properties that pigment and varnish will not do by themselves. The addition of additives is what really specializes an ink all to its own. There are many types of additives that an ink manufacturer has at its disposal. Many of them are used in such small percentages, on a per batch bases, that it would surprise you. Example, typically only 2% to 3%, by weight, of drying agents are mixed into a batch of ink.
One group of additives is oils and solvents. This group is used for flow and lubrication properties and can also influence drying characteristics. Various types of oils are linseed oil, which is obtained from the seeds of flax and tung oil, also known as china wood oil, is obtained from the seed of a nut. Mineral oils, or solvents, are petroleum-based products. In the last couple of years there has been a practice of using less mineral oils/solvents due to EPA and Government regulations concerning V.O.C.’s. It is something we have done ourselves and have found substitutes to replace petroleum-based products with those that are obtained from plant matter such as tung and linseed.
We also use special waxes to impart mar-resistance, improve slip, rub and scuff properties of ink. Most waxes are used for hard dry applications to give ink toughness and durability. Waxes can be used in two forms, a dry form that is very small in particle size or in a wet form where the wax has already been dispersed into a varnish.
A very important component of ink is its drying mechanism. Driers are used as a catalyst to promote oxidation. In the presence of driers, oxidation proceeds rapidly and the ink films dry hard in shorter periods of time. Cobalt and manganese are the two most common. Driers come in two forms, as a liquid drier or a paste drier.
Some other special additives are antioxidants, which gives an ink a stay fresh property, or a non-skinning characteristic. Soy or vegetable compounds are used to replace petroleum products as an environmental concern. We also use agents so ink will “bite” in certain types of substrates, usually a hard surface or synthetic substrate. Ph buffers are used to give balance and control between ink and fountain solution. Combinations of these components is what gives ink all of its properties and characteristics, which is basically to turn a liquid to a solid.
* GIVEN PROCESS
AN INK IS TO GIVE VISUAL CHARACTER
We can formulate ink, in varying degrees, with the use of the before mentioned components.
As a basic rule ink is formulated to give 5 characteristics in order to perform. First, ink is to give visual character to a printed surface. Visual character can be broken down into three properties:
1. Hue - indicates what color the ink is.
2. Strength - is a measure of the color’s intensity or saturation.
3. Purity - indicates how bright or dark a color is.
Types of pigments, varnishes, oils and solvents all can alter the inks hue, strength and purity.
Ink vehicle can also affect ink. It must be capable of keeping the pigment dispersed or you may have loss of strength or a vehicle that penetrates the substrate too much will lower strength.
We have to be concerned about the components that make up ink and fully test them to achieve a properly functioning product. This is why it is helpful and important that the ink supplier attain information as to what type of substrate is being used for a particular job. We are able to alter inks so that they will contain the properties, characteristics, qualities and requirements that the finished job entails.
PRINT BY A GIVEN PROCESS
Formulation of ink is greatly determined by the method of printing being used. Various types of printing, such as flexography, gravure, screen, UV, sheet fed or web inks all influence how the ink will be manufactured. Each process is most significant to the formulation of the ink. In our situation, lithographic inks are generally more viscous and paste like than other types of inks.
DRY UNDER SPECIFIC CONDITIONS
Inks are designed to dry by various means. The drying mechanism is dictated by the printing process being used and by the substrate being printed. Absorption is when ink penetrates the fibers of a substrate and is absorbed into the substrate. The degree of penetration determines the ‘dry’ ability of ink. Oxidation is when the oxygen in the atmosphere chemically combines with the varnish system converting it from a liquid to a solid. A catalyst is used, a drier, to promote the oxidation of the drying oils. Oxidation rapidly proceeds and ink films dry hard in shorter periods of time. Evaporation is when a solvent is physically removed from the ink leaving it to bind to the substrate. Heat set web is the best example of evaporation. Radiation cure is with the use of ultraviolet, or UV, drying. Special UV inks must be used for this type of drying. In most cases the printing press has some form of heat to speed the drying and setting process of the inks. Examples are IR driers, hot air knives and other forms of mechanical heat generated at or near the delivery of the press.
It is the ink manufacturers task to produce a carefully balanced formulation to ensure a high quality print at today’s press speeds, and still maintain the drying process at a satisfactory rate. We run a very thin line with the additions of driers. Not enough drier will naturally slow down the setting process, but too much drier will have the press operator pulling rollers from his/her press. Also when adding driers, too high of a percentage of drier will actually de-activate itself and never fully cure.
ADHERE TO A GIVEN MATERIAL
Ink is to adhere and bind the color to the substrate and keep it there. Pigments have little or no effect concerning adhesion. The adhesive nature of ink comes from the varnish system. Choice of varnish for specific substrates is very important. Naturally you will need different varnishes for synthetic substrates as compared to a regular coated or uncoated substrate. Adhesion to various substrates uncoated, coated, matte, vinyl, acetate, foil or other synthetic substrates must be taken into account when formulating ink.
HAVE SPECIAL RESISTANCE PROPERTIES
Inks must be able to resist certain types of chemical or physical attack. First, the ink must withstand the manufacturing process used to make it, the grinding and rolling on an ink mill, the shear of an ink mixer and the heat generated in the process. They must be able to withstand the rigors of the printing process itself. Conditions of high shear and heat generated on press as well as the addition of fountain solutions and alcohol.
Once printed, ink must be able to withstand finishing processes as cutting, folding, gluing, foil stamping, die cutting, coating or any bindery work. It also must withstand the severity of transportation. As a finished product it must withstand the rigors of the end use. Package for a product, a book, a pocket folder, a calendar etc. Since you are converting a liquid to a solid it must be able to bind, adhere, have rub and scuff resistance, heat resistance and elasticity to withstand all of these situations.
* ALL PARTIES INVOLVED
* GENERAL OBSERVATIONS
* DIRECT OBSERVATIONS
* SPECIFIC TO A JOB
ALL PARTIES INVOLVED
Now that we have the basic components of an ink its time to formulate. But before we can build an ink, one that best fits your needs, one key component that cannot be left out is YOU. A good and open dialog is needed and the need for communication is very necessary. This communication is necessary between the printer and the print buyer. It is of great importance that the print buyer covey exactly what he/she desires to achieve in their printed piece. And, in turn the printer will inform his/her ink supplier of any questions that he/she may have concerning a job.
Communication is one of the most important factors as an ink manufacturer. In order to create a product that posses the properties, characteristics, qualities and requirements of the printer, a good and open line of communication is necessary between the printer, print buyer and ink supplier. All parties involved - not just limited to printer and ink supplier, but to press operator, chemical reps, paper reps, designers, pre-press, your sales reps and the end user of the products being printed. Communication is a must to ensure all pieces work together in harmony.
DIRECT AND SPECIFIC OBSERVATIONS
Direct observations - talking to press operators to find out what they would like to see in an ink or how they would like it to perform. Try and be specific so that your ink supplier can customize the ink to fit your needs. Specific to a job - the ink manufacturer must know as much as possible about the proposed printing job. It may be a difficult layout or combinations of colors that needs special attention. A special paper, a color match. It may need special inks due to the substrate, the products end use, ink take-off being large or small, and this will affect how ink is formulated. All of these issues will in turn effect how the finished product meets the printer’s and print buyer’s needs.
YOU CAN NEVER SUPPLY TOO MUCH INFORMATION
American Offset Printing Ink
3847 Corporation Cir
Charlotte, NC 28216
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Toll Free: 800-338-4122