Experience in formulating and using fountain solution in offset printing

Offset can not be separated from water (flood fountain solution), fountain solution must be reasonably formulated according to different conditions of use, and the amount of fountain solution should also be based on weather conditions, the type and color of the ink, the actual size of the plate and other specific circumstances Differences, but also consider whether it is a net tone printing, whether it is the first color printing, whether it is stacked color printing and other factors. In the following, we will discuss the preparation and use of fountain solution by taking van der wetting powder plus fresh water to mix fountain solution as an example.

1. When formulating the fountain solution, according to the depth of the ink, the amount of dampening powder applied is generally arranged in the color sequence: magenta>black>cyan>yellow. Take the 10L plastic bucket as an example, the dampening solution used in the black version contains 3 small original spoons of dampening powder. When formulating fountain solutions for other color schemes, the amount of dampening powder can be added or subtracted accordingly.

2. The thickness of the ink layer increases and the amount of dampening powder increases. In other words, when printing large quantities of ink, in order to prevent the blank parts from getting dirty, the amount of dampening powder must be increased during preparation, instead of simply increasing the amount of fountain solution. At this point, we can observe the water on the side of the machine, with a slightly shiny layout, and no floating water. If the printed product is curled, upturned, or has a drop of rubber and drops of water, the ink roller and ink fountain are filled with water, these are all water reactions and should be promptly corrected.

3. Adjust the dosage of dampening powder according to the amount of dry oil, increase the amount of dry oil, and increase the proportion of the dose in the fountain solution.

4. Adjust the amount of fountain solution according to the workshop temperature. For example, before and after lunch, an appropriate increase of 1 to 2 squares of water consumption is required. Otherwise, due to the small number of personnel on the platform, the number of adjustments will be reduced, and evaporation of dampening fluid will increase, making the printed products dirty.

5. Adjust the amount of fountain solution according to the nature of the paper. When the printing texture is loose and there are many papers containing impurities, due to the large viscosity of the ink, the paper is easy to fluff, impurities accumulate on the blanket, and the wear of the printing plate is more likely to be dirty. At this time, the amount of the fountain solution should be increased. When printing a booklet using newsprint, it is necessary to increase the supply of fountain solution. In addition, papers that are sensitive to static electricity can increase the amount of water supplied to ensure smooth transport of paper.

6. According to the layout of the layout of the amount of fountain solution. The layout graphic is generally composed of the field, lines and dots. If the full version is a printed version of the field against white characters or lines, the amount of dampening powder may be appropriately increased. All plates with dot-level images should reduce the amount of dampening powder. Both on-site and off-site printing plates should be balanced.

Example: For the printing layout, if the amount of ink is adjusted uniformly and the amount of water is determined, the printed product usually has a slightly lighter ink at B and E, and has water spots. At this point, even if the amount of ink is not large, it will cause the opposite side to be dirty. At this time, the local water supply must be controlled. The simple method is to attach the corresponding width and width of the paper strip to the connecting roller to prevent or partially reduce the water supply to B and E, so that the local ink is saturated. So how do you do local control?

Find two bricks, processing and growth of about 3 ~ 8cm (consistent with the contact with the water roller) tightly wrapped with water velvet, sewing. Place it in a water hopper tangent to the water roll to control the local water supply. The size and position of bricks can be determined according to the conditions of points B and E.

In addition, for the "printing paste" failure common in printing, it is not necessarily caused by the fountain solution, the ink volume is too large, the ink flow is large, the dry oil is too much, the ink polarity is too strong, the layout is too fine, the printing pressure Oversized will appear paste version. Therefore, when the paste version occurs, it is necessary to analyze the cause first, and after determining the problem of the fountain solution, increase or decrease the amount of water supply or dampening and dampening of the dampening powder as appropriate.

Reprinted from: Northeast Printing Network