Inking/dampening

The concept of hthography was developed by German Aloys Senefelder in 1796. He used a stone slab with printed grease marks and dampened it with water. When a coating of ink was applied to the stone, it adhered to the grease marks and washed away from the wet areas. The ink was then transferred to paper by pressing the stone against it. 

Lithographic printing which was invented by Alois Senefelder over 180 years ago, has probably been the most widely studied of all the printing processes. Despite this, many questions remain and a total understanding of the lithographic process still eludes us. This is due largely to the complex interactions which occur on press between the ink and the dampening solution. 

In investigating these interactions it is evident that the chemistry of both the ink and dampening solution are directly involved as independent variables and that the rheology of the ink which results at the instant of printing has a strong effect on the run-nability of the ink and the faithful reproduction of the plate and clarity of image produced. 

The prevalent explanation for isopropanol s role in this kind of dampening system is that its surface tension, about 29 dynes/cm, sufficiently lowers the aqueous fountain solution surface tension to allow wetting of the inked form-roller by that solution, as illustrated in Figure 1. That is, the fountain solution wets and spreads onto, and is carried by the ink film on the form-roller to the printing plate, as a relatively thin, uniform film. 

Earlier days saw limitations to office printing where stencils, typewriter (initially with a dampening pad, then a ribbon, a golf ball, etc.), and inked rubber pad were widely used. However, small-scale or office printing can now be achieved by a range of processes, i.e. 

Equipped with a fountain and ink rollers, the inking system is like the dampening system. Depending on the quantity of ink required, the ink can be supplied to the press fountains via pipes originating from a centralized pumping station, or from point-of-use drum pumps at each press, or even by hand. These inks tend to be very viscous, which makes them rather difficult to be poured. 

In the inking step, the plates are first dampened by water rollers, followed by ink rollers, which distribute the ink from the ink fountain onto the plates. The image areas of the plate absorb ink from the ink rollers, while the water rollers keep the ink off the nonimage areas of the plate through sheer repulsion between the ink and water. With the image and nonimage areas of the plate now fuUy defined. 

Ductor roller n. The roller which is in intermittent contact with the fountain roller and transfers ink to the distribution system of the press. On a hthographic press it is also the roller, which transfers the fountain solution to the dampening rollers. 

Fountain faun-t n [ME, fr. MF fontaine, fr. LL fontana, fr. L, feminine of fontanus of a spring, fr. font-, fans] (14c) n. Part of a printing press, which contains the ink to be fed to the distributing system. In hthography, it is also the part, which feeds the water or fountain solution to the dampening rollers. 

Fountain roller n. The roller that revolves in the ink fountain. In hthography it is also the roller that revolves in the dampening solution. 

MAJOR PRODUCT APPLICATIONS paints, inks, wood finishes, powder coatings, adhesive, mastics, seals, sealants, coatings, medical, paper, battery products, drilling fluids, brake linings, bowling balls, sound dampening, plastisols, urethane foams, acoustical compounds, insulating materials... 

Fountain Solution n In lithography, generally a mixture of water, acid, buffer and a gum to prevent the nonprinting areas of the plate from receiving ink. To some fountain solutions, alcohols are added. Also known as Dampening Solution. 

Ink. If pooled, carefully dab up with a soft cloth (don t use paper towels because they may stick, making the mess worse). Then rub with a cloth dampened with warm water and Dawn dishwashing detergent. 

A layer in multilayer film structure that comprises at least one quiet film layer having noise dampening properties Ink jet pen print head body A film layer for a fluid-fillable cushion Nanoweb for engine fuel filter Rigid random coil... 

It should be reiterated at this point that surface tension control of the water-borne dampening solution is critical for lithographically-inked images to be effectively transferred to the substrate. Because of regulatory pressures regarding VOC emissions, isopropyl alcohol is being replaced by glycols, such as butyl cellosolve, to... 

Once the plate Is dampened and inked, the ink is impressed on the substrate as it is conveyed between the blanket and Impression cylinder. This printing configuration can be contained within a single printing station. Other configurations can involve the use of multiple plate and blanket cylinders which share a common impression cylinder, or where no impression cylinder is used and two blanket cylinders impress images on both sides of the substrate simultaneously as the substrate is conveyed between them. 

---