10 CHAPTER 6 STANDARDIZING THE RAW MATERIAL (INK) 6.1 Introduction Without ink, there would be no way of printing. Most of the products we see in the marketplace, on the shelves of libraries, or in many other places vital to modern living. Ink provides the means of putting into visual form the thoughts and art developed to help convey messages, inform or simply entertain. Inks provide the means of transferring color from an image carrier to a substrate, making an image visible to the human eye. Rapid expansion of India s printing market offers huge growth potential in the printing ink sector. Several global majors have entered the Indian market, such as Dainippon, Huber, Sakata and Sicpa. The market is well structured and over 70% of ink sales go to the two large and 10 1 mediumsized players in the organized sector. The unorganized sector has over 450 small players and accounts for the other 30% of ink sales. The printing ink market is showing significant overall growth. Some of the key drivers are increased urbanization, the advent of foreign publications, a revival of the fast-moving consumer goods (FMCG) sector, increasing literacy levels, increased use of printing inks in packaging, and good prospects for off shoring to India that will widen the export market (Koehler,D., et,al.,(010).
11 Total production of printing inks was 131,000 tons in volume during 010 (Table 6.1). The publication and packaging sectors together accounted for over 95% of the market volume (Table 6.). The printing ink market has had a CAGR of 14% and this CAGR is likely to continue up. Table 6.1 Printing Ink market volume ( 000 tones) Printing Ink 010 011 01 CAGR (%) (010-1) 131.6 150 171. 14 Table 6. Printing ink market volume by end use 009 1 ( 000 tons) 009 010 011 CAGR (%) (019-1) Packaging 54.5 65.1 78 19.8 Publishing 45 50 55.1 10. News paper 6.3 8.7 31.4 9.4 Others 5.8 6. 6.7 8.1 Total 131.6 150 171. 14 Table 6.3 Printing ink market share by major manufacturers 01 Sales ($ millions) Market share (%) Micro Inks 14.4 3.6 DIC 86.7.8 Sakata.6 6 Incowax Ltd 15.1 4 Sicpa 11.3 3 Others 10.7 31.6 Total 380.8 100 India s printing ink market has benefited, as all the leading global players have set up operations in India (Table 6.3). Dainippon Ink and Chemicals (DIC) of Japan, one of the world s leading ink manufacturers, set up DIC India
1 after taking over Coates of India. Flint Ink has acquired Incowax. Sakata of Japan has set up a new plant near Delhi for packaging inks. Sicpa, a leader in security inks, is well established in India. Micro Inks, formerly Hindustan Inks and now part of Huber, has 33% of the market, the largest share. Over the past five years there has been a significant increase in India s exports of printing inks. India now depends on imports only for value-added products such as process colours, flexo and gravure inks and specialized niche products. 6.1.1 Printing Ink: The Foundation of Printing Inks are composed of some basic building blocks, the specifics of which are modified depending upon the process, the substrate and the end use. As a general substance, the components of inks fall into very specific categories of chemicals: Pigment or colorant, Resin, Solvents and Additives. Combining these substances has to result in ink that will perform well on press. The colorant will convey the color(s) that project the images. Resins enable the inks to adhere within the formulation as well as to the substrate, in addition to being able to impart other characteristics to the performance and appearance of the dried ink. Resins and solvents or water are the vehicles that enable the inks to flow and be transferred through the press' printing ink train; for the most part they are liquids - solvents, oils, water. Additives are special agents required to provide special features or quality characteristics. (Rao,K.P., (003) and (Finley,C., (001). The liquid and most volatile portion of the ink is the clear solvent, which conveys the pigment and resin to the substrate. This liquid can consist of alcohols, ketones, petroleum-derived hydrocarbons, glycols or simply water. Most likely, it is a combination of several of these elements. Conventional lithographic inks use solvents made from VOC. Water and solvent based inks eliminate VOCs. Some printing inks are based on castor oil. Similarly, waterwashable ink systems eliminate petroleum-based solvents and avoid VOC emissions during printing and when the press is being cleaned. The All-India Printing Ink Manufacturers Association (AIPIMA) has asked Indian printing ink
13 manufacturers to focus on new segments and launch new products, especially in the Ultraviolet (UV) range, which is used for offset. The solvent has the primary function of converting the solid components into a fluid that is capable of being printed. The solvent must perform several tasks to achieve this goal. Selecting solvents for ink formulation requires the chemist to develop a balance between those that will have high solvency properties to bind the resin, pigments and additives into a viable package, and those that will simply act as diluents. Selection of the solvent must first satisfy the requirement that it serves in the composition of the ink. with the understanding that the solvent will present the largest and most sensitive component relative to environmental and safety/health considerations. The printer's choice of inks will vary by process and end use. With major differences stemming from the amount and nature of the solvents in the formulations relative to the amounts of pigment, resins and additives. The right ink, which will satisfy both the printer and his customer, is the one that has the lowest amount of necessary solvents, in which all constituents are neither carcinogen nor constitute other health hazards. Flammability may be an unavoidable characteristic for certain end uses and processes. Lithographic inks typically use mineral spirits and oils as vehicles. There has been an increase in use of vegetable oils to replace hydrocarbon mineral oils as environmental pressures have increased. Among the most publicized are oils that have been derived from soybeans. However, rapeseed and linseed oil have been used for many years. Based on the specific lithographic process, the percentage of these oils varies as a component of the total vehicle package. 6.1. Environmental impact of Printing Ink Not all solvents are hazardous to environment and health. Water is a solvent. Other solvents are used regularly in the foods we eat. Selecting some of these same solvents for the ink can make for safer inks. Waterborne inks are not
14 free of solvents. Atypical formulation will include some alcohols, glycols and surfactants. The amount of VOC may range from 5 to 5 percent, often with some components at quantities of less than one percent of the solution. Amines, either as ammonia or other amines, are necessary components to maintain the proper working ph of the water ink. Three main issues with the environmental impact of printing inks is the use of VOC, heavy metals and non-renewable oils. Standards for the amount of heavy metals in ink have been set by some regulatory bodies. There is a trend toward using vegetable oils rather than petroleum oils in recent years due to a demand for better sustainability. Each of these items represents a chemical substance or mixture that has potential ramifications on the health of the community or the environmental stability of the surrounding area. The Food and Drug Administration (FDA) has not approved inks, as such, for contact with any food or, for that matter, for other contact with humans in such a form as toys. The substrate sitting between the ink and the food product is considered a harrier between the two. Therefore, with some rare exceptions, inks are usually not FDA approved. There are a limited number of inks that are available for contact with food, the approval coming from the FDA for the components of the ink, but not for the ink as a finished substance. As the press runs and ink feeds through the system, the solvents will evaporate and leave the scene as air emissions. More solvent is added, and that too evaporates. Much of the question of evaporation of the solvents and their replacement has been studied to develop ink transfer systems that can curtail evaporation and reduce the amount of solvent that must be added during press runs. At the same time, research has developed high-solids resins that achieve a more liquid state with the addition of lesser quantities of solvent. This combination can bring about a considerable reduction in emissions at an improved level of quality in ink.
15 6.1.3 Tests conducted on Printing Ink Materials testing are to be done to confirm that the ink and fountain solution are compatible and will not cause problems during printing, thereby we can achieve an Eco friendly printing. Ink tacks, viscosity, fineness of grind, and strength are common tests that can help predict the performance of printing inks. Fountain solution conductivity and, particularly, ink/water emulsification curves are useful to predict the performance of the fountain solution prior to printing. A series of experiments were conducted on ink, as part of this research study. Some of the major experiments that are included in this report are stated below: (i) To find out the print quality parameters of difference inks and to select the best performed four color ink. (ii) To find the ink mileage of the given ink on paper (iii) To find out the compatibility of ink with the fountain solution 6. Evaluating the Ink Performance 6..1 Task and Objective of the Study Figure 6.1 Inks lined up for the performance test
16 The task of this study is to test seven different process inks for its performance on the paper, and objective of the study is to demonstrate their practical relevance. The points to be tested should enable relevant conclusions with regard to the printing and processing parameters. The inks used are shown in Figure 6.1. 6.. Quality and evaluation The quality of an ink can be characterized by a large number of laboratory and print parameters. These include e.g. fastness parameters, such as light fastness, chemical resistance, etc., as well as physical (tack, viscosity) and colorimetric properties (Lab). There are also a whole host of technical and processing requirements. As mentioned above, the study focuses on points with practical relevance. Therefore, instead of seeking to test just the inks compliance with ISO 1647/, it also examines other parameters, such as the print-out quality, smoothness in solids and screens, scuff resistance, gloss and the stacking or ink transfer behavior in the press. In other words, a whole range of factors that are not described or listed in any standard but that are important for everyday use. Therefore, in the context of an assessment, the requirements featured in standards must be balanced against practical uses and requirements. For example, the best Lab or dot gain values are of little use when they are pitted against unfavorable technical print or postpress properties. To address these requirements, the individual points had to be weighted depending on their impact on the overall quality. 6..3 Machine and material parameters The following is the list of the machine and material parameters featured in the study. Printing press up on which the experiments were conducted was SM 74-4-P+L. Inks: The inks featured in the study were assigned alphabetical code from A-G. Blanket used was Saphira Pro 100 and Dampening solution was FS13-00 @ 3% with Prisol IPA 10%. ph of the solution was 4.9, conductivity at 180 micro Siemens and the temperature of the solution was 1
17 degree centigrade. Paper used for this test was TNPL Radiant Print Platinum STD grade paper. The test form includes elements that make it possible to draw conclusions about area coverage-dependent ink transfer in the printed pile. It also includes all those test elements that enable a response to questions based on ISO 1647- or on the optimum interaction between ink and dampening solution. The test form is shown in Figure 6.. Figure 6. Quality Evidence Test form Before the practical tests were started, the press was test-printed using the Heidelberg inking unit and dampening solution test form and optimized for printing. A relatively high measurement workload was required to ensure that the conditions could be reproduced exactly throughout the test period, a factor that is essential as the basis for comparative tests. At the start and end of each test series, reproducibility tests were performed to ensure that the conditions remained identical.
18 6..4 Dot gain as a function of different print parameters Dot gain plays a key role in the print quality. It comprises geometric screen dot expansion and light trapping calculated by optical measurement by means of a densitometer. Figure 6.3 is the plate s copy curve used for all the print tests. Figure 6.3 Plate s copy curve for all the print tests Figure 6.4 Dot gain curve for black component
19 Through Figure 6.4 we get an idea of the differences in dot gain values for the individual inks. The different dot gain curves demonstrate that it is essential to use the particular inks as the basis for adjusting the plate curves depending on the product used. This also applies to curves that lie below or above the permitted standard range for the midtone. In this case, curves with high dot gain values are considered critical because a further reduction in the tonal values on the plate can cause tonal value jumps. The curve illustrate the different dot gain values depending on the ink manufacturers used. Among the cyan inks, for example, the tonal value for ink E is more than twice that of ink C (18% and 8% respectively). This is how the individual curve should be interpreted. Impact of the dampening solution feed on the ink density in print. Generally, the ink density in print decreases as the dampening solution feed increases. In practice, during the day or night the printer has to respond to changing conditions, e.g. heat build-up in the press, room temperature, signs of ink build-up, and a host of other parameters, by changing (usually increasing) the dampening solution feed. Figure 6.5 shows how differently the individual inks respond to these changes. Figure 6.5 Ink density variations due to dampening solution
130 Inks G, F and E show excellent results. The same is true of ink A in the 10% setting range, and the values in the 0% range are also acceptable. 6..5 Print-out quality in screen backgrounds The smoothness of the ink in conventional screens is an important quality feature that is not described in any standard. One of the main reasons for this is that there is no measuring device that can provide a clear visual result. The only evaluation that really makes sense in this context is the comparison by pairs, which is best performed by observing. The ratings are from 1 to 5 where 1 (best) to 4 (worst) Figure 6.6 shows the performance of the test inks which is graphed. The evaluation is 1 to 1.5 Very smooth and even print-out quality. Low to medium fogging, but acceptable and still good. 3 Medium to marked fogging which is in borderline for higher quality requirements. 4 Heavy fogging and roughness and is not recommended. This evaluation shows that there are clear differences in the print-out quality among the individual ink series. Inks E and B are not good. Figure 6.6 Print-out quality in screen background
131 6..6 Ghosting Ghosting refers to local differences in density that are caused by sudden changes in the ink on a print form. The degree of ghosting depends on the materials used (ink/dampening solution) and to a considerable extent on the settings of the inking unit and dampening system. The ghosting values, which were calculated using a special formula. The value is good even though there were differences between the individual ink series. The result reflects excellent settings of inking unit and dampening system. The formula to find Ghosting (U) is U = DS - DN / DS where U = Value for ghosting, DS = Average density in ghosting range. DN = Average density next to ghosting range. 6..7 Scuff resistance The term scuff resistance refers to the behavior of an ink film during a relative movement between printed and unprinted paper. The product is subject to scuffing during all the post press phases, right through to transport. Scuff resistance is not just a function of the ink, but also the printing stock. For example, uncoated paper is more prone to scuffing due to its surface structure. To neutralize the printing stock parameter in the context of the ink tests, scuff sampling was performed in the laboratory with the same printing stock. Figure 6.8 shows how the individual inks performed in terms of scuff resistance. The evaluation is based on a grade system from 1 (best) to 5.5 (worst). Figure 6.7 Samples of two scuff tests
13 Figure 6.8 Scuff resistance of process inks F series ink exhibited by far the best scuff resistance across all color components (B, C, M, Y), followed by series G and A. In some cases, the other ink series, such as series E, exhibited far less favorable results and cannot be recommended. Figure 6.7 shows the sample of two scuff tests. Sample on the left exhibits excellent scuff resistance, while the on the right is unsatisfactory. 6..8 Ink set off Ink set off from freshly printed sheets is counteracted through the use of spray powder. The amount of spray powder required depends on the printing stock, total area coverage and ink. In many printing presses, it is a common to see machines and pressroom areas covered in layers of powder. Regardless of whether this results from a lack of awareness about cleanliness, most printers would rather use too much instead of too little powder. Their major concern is to prevent ink transfer during the run. When printing the reverse side of the sheet, for example, printers prefer to increase the wash times, which results in more waste, higher auxiliary times and color fluctuations, even though good under cover removal and/or the use of suitable inks could save them a lot of
133 aggravation and problems. The print form used in this test exhibits total area coverage values of between 60% and 400% printed in a four-color overprint. Figure 6.9 Ink set off between sheets in the pile Figure 6.9 shows that, with identical powder settings, there are clear differences in the ink set off properties depending on the ink used. Evaluation is made based on a grade system from 1 (best) to 6 (worst). The red reference line at grade 3 represents light ink set off. With no powder application, six of the seven makes of ink exhibited heavy ink set off and sticking. With low/medium powder application, ink series A, E and G showed good to excellent values. However, three ink series demonstrated clear ink set off with this setting. Ink series C is ranked as borderline in this instance. With high powder application, none of the ink series demonstrated ink set off. However, the above-mentioned problems are more than likely to occur in perfecting and postpress with this high level of powder application. In addition to providing general explanations, such as the impact and importance of ink film thickness in printing, this section also focuses on laboratory tests, the color locus and gloss.
134 6..9 Impact and importance of ink film thickness in printing The ink film thickness plays a key role in a number of important print parameters, such as dot gain, slurring/doubling, contrast, brilliance, ink trapping, print smoothness, streaking, build-up, ink transfer, etc. Determining the ink film thickness based on weighed print proofs A weighed print proof is a large-area print produced on a test print unit with defined ink application volume in gsm or defined film thickness in μm. The weighed print proof is based on the difference in weight of the test print form before and after printing. To determine the film thickness in μm, the amount of ink applied (gsm) is divided by the specific weight of the ink. An analytical balance with an accuracy of ± 0.0001 g is required for the weigh-in. 6..10 Color intensity Color intensity is the area in m² that can be printed with a specific amount of ink (m²/g). In practice, however, the amount of ink in g/m² at a specific density has become accepted as a measure of the color intensity. In other words, if high color density is achieved with a relatively low ink volume, this is referred to as higher color intensity. Print proofs with increasing ink film thickness (Figure 6.10) are produced to determine the color intensity. Plotting the density against the ink volume (film thickness) produces a color intensity curve, also known as the Tollenaar curve. 0.7 g/m 1.00 g/m 0.79 g/m 1.06 g/m 0.86 g/m 0.9 g/m 0.97 g/m 1.13 g/m 1.3 g/m 1.30 g/m Figure 6.10 Proof strips with increasing ink film thickness
135 An ink is described as relatively intense when the standard color locus is achieved in the lower thickness range of 0.7 0.8 μm. Weak inks are those that lie in the upper range (1.05 1.1 μm). The target densities in printing are derived from the La*b* values and are thus always in the right target ink density range. The deviation in hue (ΔE) of the individual process colors relative to the target color must not exceed ΔE 5. 6..11 Test results for color intensity and Lab The comparison of color intensity curves for the individual colors of each of the ink series and is illustrated below. The x axis displays the ink volume in gsm while the y axis displays the ink density in print. Figure 6.11 shows the set of curves for the color yellow exhibit a broad spread in terms of the color intensity for the individual products. Comparing the inks in the medium thickness range (0.9 μm), ink B is by far the weakest, ink A lies in the mid-range, while ink F is by far the most intense with an ink density of 1.70 μm. Figure 6.11 Color intensity curves of yellow ink
136 With the exception of the magenta component of ink B, the color intensity of all other magenta components is relatively similar ( 0.1 density units) is shown in Figure 6.1. Figure 6.1 Color intensity curves of magenta ink Figure 6.13 Color intensity curves of cyan ink
137 In Figure 6.13, with the cyan components, the spread is roughly as broad as for the yellow. Here, too, ink B is the weakest, while ink F is the most intense. A again lies in the mid range. Figure 6.14 Color intensity curves of black ink The medium thickness range for black is 1.0 μm. The spread between the individual makes of ink is very large. The ranking for the weakest (B) and most intense color (F) is the same here, too. The differences uncovered here are also reflected in the practical tests. This what Figure 6.14 shows. 6..1 Comparison of ΔE curves The relationship between the hue (La*b*) and film thickness is explained in Figures 6.15. Inks F and G reach their color locus below the reference film thickness limit of 0.7 μm. Ink B reaches its color locus just short of the upper permissible limit (Figure 6.15). Figure 6.16 shows, with the magenta component, majority of the ink lie within the relevant thickness range below the maximum limit of ΔE 5. Due to its hue and color intensity, ink F does not reach the ISO range.
138 Figure 6.15 ΔE comparison of yellow ink Figure 6.16 ΔE comparison of Magenta ink
139 Figure 6.17 ΔE comparison of cyan ink If the set of curves are compared, as shown in Figure 6.17, it is clear that ink E lies outside the ISO tolerance value due to its hue. As with the yellow component, ink B only reaches its color locus in the upper thickness range. Ink F lies in the lower thickness range due to its color hue and color intensity. Figure 6.18 ΔE comparison of black ink
140 All inks reach their target color locus in the thickness range of between 0.9 and 1.3 μm (standard range for black). Depending on the hue and intensity, ink F lies just below the upper tolerance range is what is seen in Figure 6.18 6..13 Ink Gloss Gloss is important for many print products. Many commercial products, such as newspapers, catalogs and illustrated books, are not usually given an extra coating, so to them ink gloss is very important. It is important to mention that the gloss is very dependent on the printing stock used. The gloss angle (measurement geometry) used for the measurement also plays a key role. The standard measurement geometry of gloss meter is 0, 60 or 85 depending on the test sample. Therefore, it is essential that the gloss angle is provided for each gloss specification. In this case, the medium gloss range (60 angle) was used to determine the gloss values. The gloss values of the individual inks are shown in Figure 6.19. The individual ink series demonstrate considerable differences in gloss. Overall, ink series A, E and G exhibit the best gloss values. Figure 6.19 Gloss values for the ink series
141 6..14 Conclusion and Inference of the test The test results described are summarized in Table 6.4 and Table 6.5. Table 6.4 Comparative individual results and average values of ink test Parameters Ink A Ink B Ink C Ink D Ink E Ink F Ink G 1.5 3.5 1.5 Tonal value speed 1.5 3.5 Ink density consistency 3.5 4 4.5 3.5 1.5 1.5 3.5 3 1.5.5 4 3 4.5 4 1 Scuff resistance 3 4.5 4 4 3.5.5 3 Colour intensity.5 5.5 3 1 1.5 3.5 3.5 3.5.5.4 3.5 3 3.6.3 1.9 Dot Gain Print out quality Ink set off Overall impression Average value Ink G performed the best in all the key test points, followed by ink series A, E and F. Although the average value determined from the individual grades does not reflect the differences between the products at first glance, in practice there is a significant difference between grades.5, 3.0 and 3.5. In this context, it is crucial that the individual evaluations are examined, as they provide much more detail on the quality than average value. Overall, series ink B has not performed good. While ink C and D are Ok. Although all the ink series featured in these tests can undoubtedly be used for printing, they deliver major differences in quality and production reliability. The inks used in the tests were assigned individual alphabetical code for test convenience. They are: A. SAKATA PRIMO, B. HEI EDITION, C. TROPICANA, D. HEI UTILITY, E. VALUE G, F. TOYO HY BRITE and G. HEI PRIMIUM. Table 6.6, Table 6.7 and Table 6.8 show details of Ink G
14 Table 6.5 Ink performance based on test evaluation INK G EXCELLENT HEI PRIMIUM INK A VERY GOOD SAKATA PRIMO INK E VERY GOOD VALUE G INK F VERY GOOD TOYO HY BRITE INK C GOOD TROPICANA INK D GOOD HEI UTILITY INK B AVERAGE HEI EDITION Table 6.6 Details of Lab and E values of Hei Premium (Ink Code G) Measured values L a b K 13.75 1.44 5.7 C 41.48-35.85-49.4 M 46.40 74.07-6.0 Y 83.47.06 110.18 R 46.7 67.07 61.4 G 33.4-69.4 3.97 B.53 -.51-48.73 Deviation E L E a E b E BlacK 6.9 E Cyan 1.5 E Magenta 3.4 E Yellow 0.04 E Red 11.31 E Green 18.33 E Blue 7.64 Sheet 1 Sheet Sheet 3 Deviation E E E Average E BlacK 5.95 5.93 5.86 5.91 E Cyan 5.4 5.45 5.57 5.4 E Magenta.79 3.04.96.93 E Yellow 3.60 3.8 3.79 3.73 E Red.64.88.44.65 E Green 7.30 7.71 5 6.67 E Blue 6.15 5.53 6.6 5.98
143 Figure 6.0 YMC and B Dot gain curves for Hei Premium (Ink Code G)
144 Table 6.7 Details of Gloss values of Hei Premium (Ink Code G) Gloss HL MT SH AVG Black 61. 64.9 63. 63.10 Cyan 46.8 51.3 47.5 48.53 Magenta 58.7 55.8 58.9 57.80 Yellow 66.9 66.1 65.4 66.13 Table 6.8 Details of overall rating of Hei Premium (Ink Code G) Saphira Heipremium product - testing 11 Brand name: Saphira Overall Rating Total Basic Characteristics Density wet readings at centre axis control patch 1.78 1.44 1.36 1.07 Density dry readings at centre axis control patch 1.53 1.34 1.30 1.03 Ink zone opening to achieve Dv at patch 10 6.09 5.05 5.10 4.07 Ink feed sweep result % 30% 30% 30% 30% Water feed sweep result % 38% 5% 5% 34% 1% 9.5 Ink Drying smearing test result 9 5.5 9 6 Gloss 56.7 46.7 56.87 67.9 Room temperature 3oC 5.65 0.31 Total Accuracy CMYK Delta e in respect to ISO standards.34 1.94 3.73 4.11 Print contrast 8% 34% 34% 9% Plate halftone midtone 50% 35% 6% 1% 0% 1.1 pass Total Delta e in respect to ISO standards 3.19 9.73 1.1 Trapping 70.13 81.03 7.1 Total Ink split apprearence 3=Good,=Avg,1=Poor 5.13 3 3 3 9 6..15 Threats encountered during the ink standardisation test The major threats faced during ink standardisation test are stated here: Fail
145 (i) Variation in ink pigmentation: Though the Ink companies were with ISO Certified, there was noticeable difference in the colour, especially of the lighter shades. For example of Yellow colour inks. This colour variation will not reproduce the expected print quality. Figure 6.1 shows yellow inks of two different manufacturers which were having difference in the ink hue. Figure 6.1 Yellow ink with varying pigmentation (ii) Contamination in Yellow colour ink: Figure 6. shows, the yellow ink of a particular manufacturer, which was taken up for the test was found unusable as the ink was contaminated, however the ink was replaced with good ink. Figure 6. Contaminated Yellow ink
146 (iii) Quick drying of the ink in the can: Top layer of the ink in the can gets in contact with O which oxidize resulting in ink wastage, as in Figure 6.3. Figure 6.3 Oxidized top layer of ink in the used tin 6.3 The Ink Mileage Test (Yield Test) Ink mileage test is conducted to ascertain the economic aspect of printing ink ie. to find out which of the ink series gives the highest yield. It is not necessary that the ink which showed high print performance should have good mileage. Objective of the study is to demonstrate to understand how many copies of print can be pulled out from the predetermined ink quantity. This practical experiment is conducted with the same setup as that of the previous experiment (6.). The following is the list of the machine and material parameters featured in the study: Printing press up on which the experiments were conducted was SM 74-4-P+L. Inks: The inks featured in the study were assigned alphabetical code from A-G. Blanket used was Saphira Pro 100 and Dampening solution was FS13-00 @ 3% with Prisol IPA 10%. ph of the solution was 4.9, conductivity at 180 micro Siemens and the temperature of the solution was 1 degree centigrade. Paper used for this test was TNPL Radiant Print Platinum STD grade paper. The test form has been slightly modified to have almost equal area coverage for highlight, midtone and shadow area. A test image of Chess board pattern is used for this test. The test image (Figure 6.4)
147 stretches to the maximum print area to have a truthful result. Test is conducted on YMCK for each ink series. Figure 6.5 shows the density measurement at CP 000 of SM 74. Considering these factors the wet ink density was maintained as C 1.40, M 1.40, Y 1.5, K 1.70 with a ink sweep of 30%. The dampening chemistry was maintained to a conductivity of 180 micro Siemens throughout the experiment. All other dampening parameters like ph, IPA % were also monitored and maintained as per Heidelberg standards. Dampening sweep ranged between 41% to 46% since the stocks is uncoated. The experiment has to be done for each colour separately. Before commencing, all the printing units have to be thoroughly cleaned. This is to remove the residual traces of previously printed ink or wash out solution if any. While test for one colour is in progress, other units should be disengaged. For this test 1 kilo gram precisely weighed ink of each color of each series is applied to the already cleaned ink duct. The inks taken for this experiment are: A. SAKATA PRIMO, B. HEI EDITION, C. TROPICANA, D. HEI UTILITY, E. VALUE G, F. TOYO HY BRITE and G. HEI PRIMIUM. Density is maintained as stated above. Speed of the press is maintained @ 10,000 impression/hr. Density of every pull must be checked with a calibrated Spectrophotometer / Densitometer at constant intervals. The experiment said to have been completed when the ink density drop down from the set density. Either count or weigh the printed sheet for conclusion. Ink D, Hei Utility deliver the highest yield, details of yield is in Table 6.9. Figure 6.4 Ink mileage test on SM 74
148 Figure 6.5 Density measurement displayed on SM 74 6.3.1 Conclusion Table 6.9 Ink D, Hei Utility deliver the highest yield CODE BRAND NAME No of No of Copies Copies (YELLOW) (MAGENTA) No of No of Copies Copies (CYAN) (BLACK) INK A SAKATA PRIMO 136 136 133 1311 INK B HEI EDITION 148 135 149 164 INK C TROPICANA 173 15 153 14 INK D HEI UTILITY 1376 1356 136 138 INK E VALUE G 1343 1350 1354 1309 INK F TOYO HY BRITE 1340 1344 1349 1317 INK G HEI PRIMIUM 1340 135 1348 136
149 6.4 Chapter Conclusion Issues with the environmental impact of printing inks is the use of volatile organic compounds, heavy metals and non-renewable oils. Each of these items represents a chemical substance or mixture that has potential ramifications on the health of the community or the environmental stability of the surrounding area. Introducing solvent laden air extracting mechanisms can very well help to reduce pollution. Figure 6.6 is a solvent recovery mechanism at Prinovis, Dresden, Germany. This system collect the solvent laden air at source and direct it to the solvent recovery plant for processing there by arrests the emission to the atmosphere which in turn enable environmental stability of the neighborhood and health of the society. Figure 6.6 Solvent recovery plant Printing ink values % of the cost per print. Yet this ink segment alone contributes about 1100 crore. Knowing about Indian printing ink industry is very interesting. The most important observation one can make about printing ink industry is that though the volume and value are increasing by 10-15%, the average price over the years does not seem to be increasing. This indicates that
150 the growth potential is from the B and C segments of the market. The average price per kg of inks in India is significantly lower than that of developed markets. This confirms that the consumption of printing inks in India is influenced by the B&C segments. Experiments conducted with conclusion narrated in this chapter will surely be of great help to the printing fraternity to reduce wastage and thus to sustain. This will also help them to be more lenient towards eco friendliness.