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1. Unit-3 Paint Manufacturing

2. Principle of Paint Formulation For the paint technologist, the challenge of product formulation is to achieve the optimum product for the market within an agreed budget, while at the same time operating within raw material and manufacturing constraints. This demands a variety of approaches, depending on the scale of the project, which may range from the simple substitution of a raw material within an established formulation to the development of a totally new class of product using existing or new technology.

3. When considering a paint formulation, one must know the specific interaction between the paint components and substrates. This subjectis of particular importance when considering the deposition and adhesion of the components to the substrate. The latter can be wood, plastic, metal, glass, etc. The interaction forces between the paint components and the substrate must be considered when formulating any paint. In addition, the method of application can vary from one substrate and another

4. Most coatings consist of four basic ingredients, namely, a binder, pigments, solvents and additives. Some coatings may not have all of these ingredients. For example, a 100% solids plural spray epoxy contains no solvents, while an auto-motive clear coat contains no pigments. Nevertheless, it is important for the formulator to understand the roles of these basic ingredients and how they interact with one another.

5. FORMULATION CONCEPTS: PIGMENT- TO - BINDER RATIO Once the proper ingredients of a coating have been selected, they must be put together in the proper amount. A fundamental parameter of a coating is its ratio of pigment to binder. The pigment - to - binder ratio (P/ B ) is simply the ratio of the weight of pigment to the weight of binder. A gallon of paint containing 8.0 lb of pigment and 4.0 lb of binder therefore has a P / B of 2.0. Topcoats typically have a P / B of 1.0 or less, while primers often have a P / B of 2.0 – 4.0 . All other things being equal, gloss coatings will have a lower P / B than flat coatings.

6. FORMULATION CONCEPTS: PIGMENT- VOLUME CONCENTRATION The pigment- to - binder ratio is an easily measurable and helpful concept in paint formulation. A concept with more far- reaching consequences is the pigment -volume concentration (PVC). The latter is the ratio of the volume of pigment ( Vp ) to the volume of pigment plus the volume of solid binder ( Vb ), as shown in the following:

7. PVC= Vp / Vp + Vb When multiplied by 100, this parameter is referred to as the % PVC. From the above, it is obvious that two coatings can have an identical P / B value, but dramatically different PVC values, simply by using pigments of different Densities.

8. A term related to the PVC is the critical pigment - volume concentration (CPVC). The latter is the PVC at which there is precisely the right amount of binder to provide a thin coating over the complete surface of each particle of pigment. At levels above the CPVC, there is insufficient binder to wet all of the pigment, while below the CPVC , there is an excess of binder.

9. FORMULATION CONCEPTS: DENSITY, WEIGHT SOLIDS AND VOLUME SOLIDS Quantities such as density, weight solids and volume solids, along with % pigment and % binder, are often referred to as a coating ’s ‘ physical constants ’ . The formulator needs to understand these quantities, and how to measure or calculate them.

10. The density of a coating, or its weight - gallon, is usually expressed as pound per gallon, and is conveniently measured by using a pyncnometer . The latter is simply a device that holds a precisely known volume of liquid. In the paint industry, it is often called a weight - gallon cup. Since the various ingredients in the formula have a wide range of densities, the density of the finished product is a quick and easy way to tell if a substantial error occurred when making a particular batch of coating.

11. The weight solids of a coating, sometimes referred to as the % non - volatile by weight, is simply the weight of solid material divided by the coating’s total weight. For example, if a 100 - g sample of liquid paint contained 20 g of pigment, 30 g of resin solids, 2 g of non- volatile additives and 48 g of solvent, its weight solids is 52%. Weight solids can be calculated from the formula of the coating, or measured by determining the weight of non- volatile material remaining after a known initial weight of coating has been evaporated to dryness in an oven.

12. Paint consist of 4 basic components: 1. Resin 2. Pigment 3. Solvent 4. Additives The performance of coating is enfluenced by the selection of these components and the relationship between them. Several relation plays an important function in the overall performance of the coating.

13. Formulating Ratios are: 1. Pigment/Binder ratio P/B=Mp/Mb Where, P/B= Pigment/Binder ratio Mp= Mass of pigment Mb= Mass of binder

14. 2. PVC (Pigment Volume Concentration) The ratio of the volume of pigment to the volume of total nonvolatile material present in a coating. The figure is usually expressed as a percentage. Coating are usually compose of a mixture of multiple pigments and binder.

15. PVC= Volume of pigment/Volume of total solid = Vp /( Vp+Vb ) Where, PVC= Pigment volume concentratation Vp = volume of pigment Vb = volume of binder

16. 3. CPVC (Critical Pigment Volume Concentration) The point where there is just sufficient binder present within a paint to cover each extender particle with a thin layer and fill all voids between particles. CPVC can be calculated from oil absorption (QA) as follows: CPVC=1/(1+QA ρ /K) Where, CPVC= Critical Pigment Volume Concentration QA= Oil absorption, ρ = specific gravity of pigment K=100xspecific gravity of binder

17. 4. Extender substitution at constant gloss Past a certain level, as PVC increases gloss decreases. An extenders serves the dual function to impart specific properties to the coating and reduced the overall cost. By substituting an extender with a lower oil absorption it is possible to increases the PVC while not adversely affecting gloss. E=A1*D2/A2*D1 Where,

18. E= Extender substituting factor A1= Oil absorption of substituted extender (%) A2= Oil absorption of substituting extender (%) D1= Density of Oil substituted extender (%) D2= Density of Oil substituting extender (%)

19. 7 principles of pigment color matching The pigments available for the paint are divided into nine basic shades, such as red, orange, yellow, green, purple, blue, white, black, and metallic luster depending on the color they present. Different wavelengths exhibit different tones, and the same wavelength range has different sensitivity to hue changes. At the same time, the brightness of the color varies with the purity of the hue or color.

20. therefore, in the design of pigmented coatings, the choice of pigments is very important and should be formulated according to the color code of each pigment . In addition, the physical properties of the selected pigments such as particle size, tinting strength, hiding power, suspensibility , optical fastness, heat resistance, and the like are also considered.

21. 7 principles of pigment color matching in paint formulation design 1. When color matching of paints, use five basic colors of red, yellow, blue, white and black for color matching; 2. When color matching of paints, try to use coloring pigments with similar properties to mix colors, so as to avoid structural or composition changes when the paints are used, and the color of the paints varies;

22. 3. In the specific color matching, try to choose the color matching of the same coloring pigments with different brightness, so that the color of the paint with the primary and secondary, light and dark coordination can be formed; 4. In the color matching of paints, the difference in density between different colored pigments should not be too large;

23. 5. In the color matching of the paint, there should be no reaction between the colored pigments. For example, when the lead, copper, and mercury-based pigments are mixed with the sulfur-containing pigment, the color becomes dark; when the red C is mixed with the chrome yellow, the red color is easily faded;

24. 6. In the color matching of paint, if you want to improve the color brightness of the paint, you can add a small amount of dye; if you want to improve the color purity of the paint, you can add a proper amount of white pigment to cover up a small amount of noise in the paint; 7. In the same coating formulation system, the variety of coloring pigments should not be too much, so as to avoid the variegation and make the paint color dull.

25. Production process paint Laboratory. Before production starts each separate paint has a unique formula developed for it in the laboratory. ... Weighing the raw materials. ... Dispersion. ... Pre-mixing. ... Grinding the pigments. ... Fineness inspection. ... Colour inspection. ... Stability inspection.

26. The paint manufacturing process is a complex and intricate one that involves a wide range of steps and materials to produce a high-quality product. From the selection of raw materials to the mixing and blending of various components, each step in the process plays a crucial role in determining the final characteristics of the paint. In this article, we will take a closer look at the various stages involved in the paint manufacturing process and how they come together to create a durable and attractive coating for a wide range of surfaces. 

27. The main steps in the paint manufacturing process Raw material selection and preparation : Raw materials are carefully selected and prepared for use in the paint manufacturing process. This typically involves grinding and mixing the pigments and other ingredients to create a homogeneous mixture.  Formulation and blending : The paint base is combined with additional ingredients, such as solvents and additives, to create the final paint product. This step involves carefully measuring and mixing the ingredients to ensure the desired properties and characteristics of the finished paint. 

28. Filtering and fining : The paint is filtered to remove any impurities and fine particles, which helps to improve its appearance and performance.  Packaging and labelling : The finished paint is packaged in containers, such as cans or buckets, and labelled with information about the product, such as its color, finish, and recommended uses.

29. Raw Materials and Their Preparation  Paint is typically made from a combination of raw materials, including solvents, pigments, binders, and additives. These raw materials are carefully selected and combined in precise proportions to create the desired properties and characteristics in the finished paint.  The specific raw materials used in paint manufacturing will vary depending on the type of paint being produced. For example, the raw materials used in water-based latex paint production will be different from those used in oil-based alkyd paint. 

30. List of Raw Materials Used in the Paint Manufacturing There are many different raw materials that are combined and used in the preparation of paint.Some common raw materials used in paint manufacturing include:  Solvents Solvents are used to dissolve the other ingredients in the paint and control the consistency of the finished product. Common solvents used in paint include water, alcohol, and mineral spirits. 

31. Pigments Pigments are the colorants that give the paint its color. They are typically finely ground minerals or chemicals that are insoluble in the paint's solvent. Common pigments used in paint include titanium dioxide, zinc oxide, and iron oxide.  Binders Binders are the glue that holds the pigments together and adheres the paint to the surface it is applied. Common binders used in paint include latex, acrylics, and alkyds. 

32. Additives Additives are substances added to the paint to improve its performance or alter its properties. Common additives used in paint include preservatives to prevent mold growth, flow agents to improve the paint's application properties, and UV absorbers to protect against fading from sunligh t. 

33. Process of Paint Manufacturing To prepare these raw materials for use in paint manufacturing, they must undergo several processing steps. This typically involves grinding and mixing the pigments and other ingredients to create a homogeneous mixture. The resulting paint base is then packaged and shipped to paint manufacturers, where it is further processed and combined with additional ingredients to create the final paint product. The paint manufacturing process typically involves the following steps: 

34. Selection of raw materials The first step in the paint manufacturing process is the selection of raw materials. These include pigments, binders, solvents, and additives that will be used to create the desired paint color and properties. The selection of raw materials is crucial to the quality of the final paint product, and manufacturers carefully choose each component to ensure that it meets their specifications. 

35. let down The second step, let down, includes final mixing, dilution, filtering and transferring the final product for packaging into containers, such as one-gallon buckets or large drums. During the let down process, additives, such as toners, may be added for features, such as gloss levels.

36. Mixing and blending Once the raw materials have been selected, they are carefully mixed and blended in the proper proportions to create the base paint mixture. This is typically done using large industrial mixing equipment, such as blenders or agitators, to ensure thorough and consistent mixing. 

37. Grinding and milling After the base paint mixture has been created, it must be ground and milled to achieve the desired consistency and smoothness. This is typically done using a mill, which can be either a horizontal or vertical roller mill. The paint is fed into the mill, where it is ground and milled until it reaches the desired consistency. 

38. Quality control and testing Before the paint is packaged and shipped to customers, it must undergo thorough quality control and testing. This involves evaluating the paint's physical and chemical properties, such as its colour , viscosity, and drying time, to ensure that it meets the manufacturer's specifications and customer requirements.

39. Packaging and shipping The last step in the paint manufacturing process is packaging and shipping the finished product to customers. Paint is typically packaged in containers such as cans or drums and shipped to retailers or directly to consumers.  Overall, the paint manufacturing process is a complex and highly controlled one that involves a wide range of steps and materials to produce a high-quality product. By carefully selecting and blending raw materials, grinding, and milling the paint to the desired consistency, and conducting thorough quality control and testing, manufacturers can produce a wide range of durable and attractive paint coatings for a variety of applications. 

40. Final Product Finishing and Quality Control  Final product finishing and quality control in paint manufacturing is a critical part of the process, as it ensures that the paint produced meets the required specifications. It involves inspecting the paint for any flaws in colour , gloss, sheen, and other characteristics, as well as ensuring it complies with the relevant safety, environmental, and regulatory standards. The three steps involved in the final product, finishing and quality control are as follows:

41. The First Step The first step in the finishing and quality control process is to inspect the paint for any defects. This is done by checking the paint’s color, gloss, sheen, and other characteristics, to ensure that all are within the desired specifications. If any flaws are found, the manufacturer will take steps to rectify them, either by adjusting the paint’s formulation or by changing the production process.  

42. The Second Step Once the paint is deemed acceptable, it is tested for compliance with relevant safety, environmental, and regulatory standards. This includes testing for volatile organic compounds (VOCs), lead levels, and other hazardous substances. The paint is also inspected for accuracy and consistency in the various formulations.  

43. The Final Step Finally, the finished product is packaged and shipped to the customer. During this stage, the paint is inspected one last time to ensure that it meets the customer’s specifications. This is done to ensure that the customer is satisfied with the product and that the paint will perform as expected . 

44. Environmental Considerations in Paint Manufacturing   Paint manufacturing is an essential industry, providing products to give homes, businesses, and other structures a fresh, fresh look. However, the paint manufacturing process can create environmental hazards if not effectively managed. Fortunately, there are a variety of environmental considerations that paint manufacturers can take to reduce the environmental impact of their operations

45. Initial Step for Environmental Consideration for Paint Manufacturing The first environmental consideration for paint manufacturing is the type of raw materials used in the production process. Many paints contain volatile organic compounds (VOCs) which can be released into the atmosphere during the manufacturing process. Paint manufacturers should look for low-VOC or VOC-free raw materials whenever possible to reduce air pollution. Additionally, paint manufacturers should look for other non-toxic raw materials, such as plant-based resins, which are biodegradable and have a lower environmental impact. 

46. Second Step for Environmental Consideration for Paint Manufacturing Another environmental consideration for paint manufacturers is the use of hazardous chemicals. These chemicals can be released into the environment during the manufacturing process, leading to water and soil contamination. Paint manufacturers should use safer alternatives, such as water-based paints, whenever possible to reduce their environmental impact. 

47. Final Step for Environmental Consideration for Paint Manufacturing Finally, paint manufacturers should also consider the disposal of their waste products. Many hazardous chemicals used in the paint manufacturing process can be difficult to dispose of safely. Paint manufacturers should look for ways to reduce their waste, such as recycling and composting, and should ensure that any waste materials are disposed of properly.  By considering these environmental considerations, paint manufacturers can reduce their environmental impact and ensure their operations are as sustainable as possible. 

48. Overall, the paint manufacturing process is a complex one, but with the right materials and processes, high-quality, durable paint can be produced. By understanding the basic steps in the process and controlling the parameters throughout, manufacturers can ensure consistent results. In addition, automation and monitoring systems can help ensure the process is efficient and cost-effective. While paint manufacturing may be complex, the result is a product that is essential for a variety of industries and applications. 

49. Raw Materials A paint is composed of pigments , solvents, resins, and various additives. The pigments give the paint color; solvents make it easier to apply; resins help it dry; and additives serve as everything from fillers to antifungicidal agents. Hundreds of different pigments, both natural and synthetic, exist. The basic white pigment is titanium dioxide, selected for its excellent concealing properties, and black pigment is commonly made from carbon black. Other pigments used to make paint include iron oxide and cadmium sulfide for reds, metallic salts for yellows and oranges, and iron blue and chrome yellows for blues and greens.

50. Solvents Solvents are various low viscosity, volatile liquids. They include petroleum mineral spirits and aromatic solvents such as benzol , alcohols, esters, ketones , and acetone. The natural resins most commonly used are lin -seed, coconut, and soybean oil, while alkyds, acrylics, epoxies, and polyurethanes number among the most popular synthetic resins.

51. Additives Additives serve many purposes. Some, like calcium carbonate and aluminum silicate, are simply fillers that give the paint body and substance without changing its properties. Other additives produce certain desired characteristics

52. in paint, such as the thixotropic agents that give paint its smooth texture, driers, anti-settling agents, anti-skinning agents, defoamers , and a host of others that enable paint to cover well and last long.

53. Design Paint is generally custom-made to fit the needs of industrial customers. For example, one might be especially interested in a fast-drying paint, while another might desire a paint that supplies good coverage over a long lifetime. Paint intended for the consumer can also be custom-made. Paint manufacturers provide such a wide range of colors that it is impossible to keep large quantities of each on hand. To meet a request for "aquamarine," "canary yellow," or "maroon," the manufacturer will select a base that is appropriate for the deepness of color required .

54. The Manufacturing Process Making the paste 1 Pigment manufacturers send bags of fine grain pigments to paint plants. There, the pigment is premixed with resin (a wetting agent that assists in moistening the pigment), one or more solvents, and additives to form a paste.

55. Dispersing the pigment 2 The paste mixture for most industrial and some consumer paints is now routed into a sand mill, a large cylinder that agitates tiny particles of sand or silica to grind the pigment particles, making them smaller and dispersing them throughout the mixture. The mixture is then filtered to remove the sand particles. 3 Instead of being processed in sand mills, up to 90 percent of the water-based latex paints designed for use by individual homeowners are instead processed in a high-speed dispersion tank. There, the premixed paste is subjected to high-speed agitation by a circular, toothed blade attached to a rotating shaft. This process blends the pigment into the solvent.

56. Thinning the paste 4 Whether created by a sand mill or a dispersion tank, the paste must now be thinned to produce the final product. Transferred to large kettles, it is agitated with the proper amount of solvent for the type of paint desired. Canning the paint 5 The finished paint product is then pumped into the canning room. For the standard 8 pint (3.78 liter) paint can available to consumers, empty cans are first rolled horizontally onto labels, then set upright so that the paint can be pumped into them. A machine places lids onto the filled cans, and a second machine presses on the lids to seal them. From wire that is fed into it from coils, a bailometer cuts and shapes the handles before hooking them into holes precut in the cans. A certain number of cans (usually four) are then boxed and stacked before being sent to the warehouse.

57. Straining the paint Straining paint is a process that involves filtering out any solid particles or impurities that may be present in the paint. The painter will likely use a 200- or 300-micron strainer on primer surfacers ; 200 should adequately clean up solventborne clearcoats before application. If you use a 125-micron strainer, thick primers will take forever to filter through the small holes.

58. Thinning The process of thinning paint involves a relatively small amount of water: 2-4 cups for every five gallons of paint. This small amount of water improves the workability of the paint without diluting it or leading to negative results. e.g. Mineral spirits (North America) / White spirit (United Kingdom and Ireland) Acetone. Turpentine. Naphtha .

59. Paint thinners are solvents that can dissolve paint and reduce viscosity of paint or “thin” it for use in sprayer applicators or when simply needing a thinner mixture to work with. Because they dissolve paint they aid in removal of paint on brushes, rollers and general cleanup of spills or splatters.

60. A thinner is a volatile solvent that is used to dilute or extend oil-based paints or cleanup after use. Common solvents used as paint thinner chemicals include mineral spirits, mineral and true turpentine, acetone, naphtha, toluene, methyl ethyl ketone (MEK), dimethylformamide (DMF), glycol ethers and xylene .

61. Tint Tint is a pigment mixture you can add to paint to give the paint color as well as to increase opacity. If you want your basic white paints to cover better you want to introduce a specific color and volume combination. Tint refers to any hue or mixture of pure colors to which white is added. Pastel colors are generally tinted colors. Tinted color remains the same color, but it is paler than the original.

62. Tinting Tinting is the process of adding two or more colors to a system. Tint machines or color dispensing machines are used to tint the standard paint bases. The tinting strength of a paint film is the ability of a colorant or a pigment. The finer the pigment has been ground, the higher the tinting strength. The higher the tinting strength of a paint, the longer it will conserve its colour by mixing with white.

63. Tinting Strength As tinting strength is directly influenced by the pigment type and concentration used in the coating system, it is an important economic factor when selecting one paint over the other. Differences in tinting strength result from batch-to-batch variations during colorant manufacturing and are therefore a crucial test for incoming QC at a paint maker. If the tinting strength of the colorant is not within the specified limits, the paint formula needs to be adjusted to achieve the required color shade.

64. Tinting Strength Tinting strength can be influenced by using an optimized wetting/dispersing additive at an optimized dispersing time. Tinting strength is the ability of a colorant or pigment to alter the color of a paint film. It is determined at the wavelength of maximum absorption using the absorption and scattering coefficients K/S of standard and batch. Tinting strength is expressed in %. The tinting strength of a colour is determined by the type of pigment, the amount of pigment and the fineness of the grinding.

65. Phenomenon of wetting in paint The wettability of a solid surface is a function of the relative surface tensions of the paint and the solid surface. In order to ensure good wetting of the substrate, the surface tension of the substrate must be as high as possible. Wetting is the ability of a liquid to maintain contact with a solid surface, resulting from intermolecular interactions when the two are brought together.

66. Wetting ability is a liquid’s ability to maintain contact with another surface, to spread easily and uniformly over the surface of another solid or fluid. A liquid with high wetting ability forms a thin, continuous film when it spreads over the surface of something. A liquid’s wettability – its degree of wetting – is determined by a force balance between cohesive and adhesive forces.

67. At the point in which the fluid touches the surface of a solid – the liquid-solid surface interface – if the fluid’s molecules have a stronger attraction to the molecules of the solid surface than to each other – the adhesive forces are greater than the cohesive forces – wetting of the surface occurs. On the other hand, if the fluid molecules are more strongly attracted to each other than the solid surface’s molecules – the cohesive forces are greater than the adhesive forces – the liquid does not spread uniformly across the surface; instead it beads up.

68. Wetting agents are substances that reduce a liquid’s – for example, water’s – surface tension, and allow it to spread evenly across a surface, thus increasing its wetting ability. Reducing the surface tension lowers the amount of energy required to spread drops onto a surface, thus weakening the liquid’s cohesive properties and enhancing its adhesive properties.

69. Grinding in paints The composition of the grinding paint is a combination of paint viscosity and the volume fraction of pigments. For effective grinding, the paint must be in a plastic flow state with a relatively high pigment content . The wet grinding process occurs when a product is transformed from solid to liquid, regardless of its viscosity: paints, inks, enamels, nail varnish, among others.

70. Grinding in paints Pigment particles do not usually exist as primary particles but instead as aggregates or agglomerates. Reduction of these clusters to primary particles is necessary in order to obtain optimum visual, economic and performance properties of pigments. Grinding refers to mechanical breakdown and separation of particle clusters to primary particles, and follows generally after the pigment has been wetted. The effectiveness of grinding depends on the magnitude of forces holding the individual particles together in clusters.

71. The exact breakdown mechanisms of clusters are not clear, however, but are generally brought about either by smearing (shearing), or smashing (impact) types of dispersion equipment. Some of the most typical machinery for dispersion are reviewed in Lambourne and Strivens (1999). For laboratory made paints, such as experimental novel antifouling formulations small scale high-speed dispersers and mechanical shakers can be used

72. Modern grinding machines have continued to evolve, incorporating advanced technologies such as computer numerical control (CNC) systems, which allow for highly precise and automated CNC grinding operations. Today’s grinding machines are capable of achieving extremely fine finishes and accurate dimensions on a wide range of materials, making them indispensable in modern manufacturing processes.

73. Grinding Fineness refers to the degree of smoothness or uniformity of the finish of the system. The fineness of grind is the degree of uniformity and extent of fineness to which particles/pigments are ground in paints and inks. Most of the pigments and extenders used in paints are processed to very fine particle sizes. This particle size ranges from 2 to 50 Microns. However, this fine size also needs to be: uniformly processed to achieve a uniform dispersion and ensure the quality of dispersion in inks and paints.

74. importance to measure the fineness of grind The fineness of grind is not only limited to finish and aesthetics. But it can also facilitate a lot of other optimization and standardization processes. Some of the reasons to check the fineness of grind are as follows: Ensure optimum grinding of paints, inks, etc., for physical and physiochemical properties Grinding/high shear dispersion is a costly process. Hence, evaluation and optimization of the fineness of grind can save a lot of costs and other resources. Inbound/outbound product and quality rationalization. Optimization and selection of efficient processes and grinding media .

75. Dispersion Dispersion is a key phase in paint manufacturing. When it comes to emulsified paints, for example, it is widely considered as the most important phase. The goal in the dispersion phase is to cause most of the agglomerated pigments and fillers that are part of the formula to be stably separated as individual particles.

76. A dispersion is a system in which distributed particles of one material are dispersed in a continuous phase of another material. The two phases may be in the same or different states of matter. Dispersions are classified in a number of different ways, including how large the particles are in relation to the particles of the continuous phase, whether or not precipitation occurs, and the presence of Brownian motion. In general, dispersions of particles sufficiently large for sedimentation are called suspensions, while those of smaller particles are called colloids and solutions.

77. Process of dispersion Pigment dispersion is the process of suspending insoluble pigments in a liquid medium, typically water or organic solvent, so that they can be used in inks paints and coatings. Traditionally, pigment dispersion is comprised of three main steps; wetting, deagglomeration , and stabilization . In paints, the dispersed phase is solid while dispersion medium is liquid.

78. When white light is passed through a glass prism it splits into its spectrum of colours (in order violet, indigo, blue, green, yellow, orange and red) and this process of white light splitting into its constituent colours is termed as dispersion.

79. Pigment dispersion Pigment dispersion is the process of suspending insoluble pigments in a liquid medium, typically water or organic solvent, so that they can be used in inks paints and coatings.  Traditionally, pigment dispersion is comprised of three main steps; wetting, deagglomeration , and stabilization.  These three steps are outlined in further detail below.

80. Pigment Wetting When solid pigments are first added to the liquid medium they are agglomerated and air is entrapped in the surface of the pigment agglomeration.  In order for proper wetting to occur the air entrapped in the pigment needs to be replaced with the liquid medium.  The use of a wetting agent speeds up the process and ensures complete wetting of the pigment.

81. deagglomeration Once complete wetting of the pigment particles is achieved, the large agglomerations of pigment must be broken up to reduce the particle size.  This is commonly achieved through mechanical shear via the grinding mill.  Reduction of the surface tension in the liquid medium allows for faster deagglomeration and a more homogeneous particle size in the dispersion.

82. Stabilization The deagglomerated pigment particles now must be stabilized to prevent reagglomeration .  In this step, dispersants are added that will adsorb onto the pigment particles and keep them separated.  Stabilization of pigments in suspension can be classified as either electrostatic or steric .