Dot gain

Density and Ink Film Thickness. Because ink film thickness directly impacts color, it is important to control film thickness on press. The amount of ink transferred to paper, along with a related factor, dot gain, which refers to how the halftone dots spread under the pressure of the printing process, is the tool by which a press operator monitors color on press. 

Guidelines for uniform density and dot gain limits have been estabHshed. These criteria ate the standards used to control the press. A densitometer is used to measure these standards and measurements ate made on sheets removed as the press is mnning. The operator then uses these measurements to guide press adjustments, primarily ink flows, to correct the printed result to standard (8). 

High-definition process printing better dot structure, lower dot gains... 

For example, an ink may contain a mixture of cyclohexanone with an evaporation rate of 0.2 and butoxyethanol (Butyl Cellosolve) with an evaporation rate of 0.07. Additional factors to take into account when choosing the solvents are the interaction of the solvent with the substrate, e.g., swelling of polymeric substrates enhances adhesion. Surface tension will influence print quality and dot gain with high surface tension solvents leading to smaller drops. 

Additives are components added in smaU amounts for a variety of purposes. Surfactants such as sUoxanes and flouro surfactants reduce surface tension and control dot gain. Acrylic leveUng agents are used... 

M.A. Coudray, Understanding and Controlling Halftone Dot Gain, Screen Printing, June 1992. 

Required by Colorant characteristics, halftone orientation strategy Dot gain, electrical and mechanical drift, d , ... 

April 30,1986. Photopolymer positive surprint color proofing film based on epoxy acrylate monomer exhibits low dot gain, low time dependence of toning and good tonal range. Binder can be methyl-methacrylate/ethyl acrylate/acryhc acid copolymer, preferably crosslinked with zinc ions and plasticized with a second acrylate monomer and a mixture of triacetin and trimethylol propane. 

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