What faults can occur in lithographic printing? What remedies are there?

The faults of lithography though also have many similarities with letterpress. However, the key factors in lithographic failures are mainly due to the use of water. That is to say, one of the main causes of lithographic failure is water.

Of course, lithographic printing is indirect printing , and it is understandable that there may be more problems due to the addition of a transfer process.

(1) Dirty version (Greasing, Scummning).

This is a term with a broad definition. In short, a dirty version means that there is color (or ink) where there should be no color (or ink). Therefore, any phenomenon that there is color (or ink) on the plate (also reflected on the printed matter) where there should be no color (or ink) can be collectively referred to as a dirty plate.

Dirty version also manifests as thickening of the graphic and text of the printed product, spreading and expanding of the imprint, paste of the network cable (dot) into one piece, and so on.

Dirty plates can be divided into two categories: oily and floating.

In oil dirty, it can be divided into two contents: greasing and scumming, but the boundary between them is not so clear, and generally speaking, it seems difficult to distinguish them. Generally speaking, oiling refers to the irregular expansion of graphics and text, resulting in damage to the printed matter and deformation of the printed matter pattern. Therefore, when the ink is oily, it can also be dirty from time to time (Dirtyworking), and cause the dots of the printed matter to be elongated (so-called tails) and feathery. Staining is the spread of ink spots in a large area, often appearing in relatively large blank areas (note that this is very similar to the phenomenon of floating dirt).

Strictly speaking, oil stain mainly refers to a phenomenon that the printing plate is easy to feel grease (ink) (that is, the printing plate has poor grease resistance), while floating dirt is mainly caused by ink, and generally it appears relatively evenly On the entire layout, the hydrophilic part of the printing plate still has good fat resistance (that is, there is no disadvantage to the plate). Therefore, it can be generally considered that oil stains are mainly caused by printing plates, while floating dirt is mainly caused by inks.

1. From oil ( greasy ) (also known as greasy version, paste version Greasing)

(1) Phenomenon: The lines of the printed matter spread out and expand, and the graphics and texts are not clear and complete. In the non-graphic (blank) area, there is a dirty phenomenon. Pieces of oil (ink)-like substances were also stuck on the blanket.

(2) Reason: The water-absorbing area on the printing plate forms an oil-absorbing (ink) center. Surfactants in the ink or paper coating have migrated onto the absorbent areas. The acid value of the binder in the ink is too high. The water is too weakly acidic (thus preventing the peach gum membrane from protecting itself). The acidity of the water is too strong (during the printing process, there must be some degree of chemical action on the plate, that is, the metal of the plate is decomposed by the acid in the potion, so that the plate can be kept clean. However, this action needs to be very slow to make the plate The adhesive film is not damaged or disappears. If the corrosion is too strong, the printing plate may be stained with ink and gradually damaged. When the acidity of the potion is too strong, the chemical reaction of the plate is too fast, so that the adhesive film cannot support. In addition, when using When the lead paste drying oil is used, especially when the amount is too much, the highly acidic potion will destroy the drying oil and produce a smooth film on the printing plate. This film generally contains lead phosphate Or lead chromate, or a mixture of both, because lead chromate is a yellow substance, so the whole layout tends to turn yellow. Because this film layer will hinder the control of wetting, the result will be dirty from oil). Ink is too thin. Too oily. There is not enough water on the plate. The pressure of the form roller (also known as the ink form roller) is too high. The quality of the edition is too poor. The desensitivity of the non-printed area is not handled well. Improper use of desiccant. Poor water quality and improper installation.

(3) Solution: The thickness of the ink film layer of the printed matter should be appropriate, not too thick. The ink should be thick and less oily. The acid value of the binder used in the manufacture of ink should be lower. Properly increase the acidity of the potion. Try adding some lanolin, beeswax or sodium silicate to the ink. Check the quality and printing speed of the plate.

2. Scumming, Scumming

(1) Phenomenon: Many ink stains appear in the non-graphic area of the printed matter.

(2) Reason: The imprinting force and operation of the printing machine can destroy the desensitizing film on the printing plate, which acts as isolation, thereby exposing the metal. These exposed places will be immediately covered by traces of surfactants, polar substances, free fatty acids, etc. effect. These places will absorb ink, causing stains in non-graphic areas and destroying the quality of the entire print. Smearing can also occur when excess residual coating is left on the plate during development. In addition to improper handling of induction. Poor gluing. Link material is too thin. The ink is too oily, too soft, and not viscous enough, which causes the plate roller to slip and at the same time makes the water roller dirty. The yield value of the ink is too high. The acidity of the water is too low. There is not enough water on the plate. The ink absorber absorbs ink. There is dirt in the blank area of the original.

(3)解决办法：油墨中加入一些稠的连结料。增加药水的酸性。增大给水量。减少油墨配方中的油和脂的含量。用浓度大的油墨，使印迹薄一些。用表面张力比较高的药水，表面张力太低时，出于纸张中的水溶性表面活性剂、油墨中的极性组分以及药水中的可洗性皂类等的影啊，在版上的油墨膜和水膜之间就不可能得到适当的界面张力，这就可能导致起脏。减少干燥剂用量。调整印版及橡皮滚筒之的压印力，勿使滚简同有不均匀的压力，从而磨损版面。换用快平的树脂型油墨。

3.浮脏，糊版(Tinting)

(1)现象：印版上布满了轻微的器色，并转移到了橡皮布上，又传递给了印剧品，使印刷品的非图文区也布满了轻微的颜.色。印版上的璧色虽然可以擦去，但很快义会出现。水中有颜色。

According to定义可郎知道，这种脏版是由于油墨或是其组分浮在水上或溶于水中所引起的。所以，浮脏有时又叫油墨渗色或化水Bleeding) ，

(2)原因：印刷涂料纸时比较容易出现浮脏。这是因为纸张中的表面活性剂被浸取了出来，形成了油墨在水中的乳化体而布满了印版的吸湿部分。油墨中的连结料粘度太低，有时形成了油在水中的细小乳化体，形成浮脏。油墨中采用了亲水颜料(例如色淀类颔料都比较亲水)。油墨不成熟、油墨中所用的颜料亲油性差，颜料末被连结料所充分润湿（例如铬黄制的油墨在刚生产出来时铬黄颜料就极易“跑”到永中去)。在树脂型油垦中，采用低温分散型连结料而油墨油的含量又比较高时，容易引起乳化。

( 8)解决办法：油墨生产出来后应当有一个足够的存放(成熟)时间。油墨中应当柔用亲油性好的颜料，或表面用憎水材料处理过的颜料。油墨中的连结料对颜料应有良好的润湿性。降低药水的酸性，给水量亦可少些。加入稠粘的连结料。

(二)脱墨，也称金属辊脱墨(Stripping Rolier Stripping )。

1.现象：墨辊上油墨分配不幻，有些地方不粘墨，尤其是金属辊子更为严重，能使印版出现空白区。

2.原因：油墨对药水有敏感（油墨亲水乳化）性。油墨失去连结作用。金属辊表面形成了一层磷酸盐，从而排斥油墨。水太大。药水酸性太大，润湿了金属轮。

3.解决办法：i减少水.量。降低药水的浓度。在油圣中诩入粘度比较大而长（即流动性好）的连结料或撤淡剂。金属轮可用化学法或机.械法〈浮石磨擦罅）处理一下，并充分干燥之。换用亲脂的铜轮或硬质象F轻。换用新的抗水性好的油墨。

(三)堆墨，又称起厚(Piling)。

1.现象：颜料从油墨中分离出来，堆集在版和橡皮布上，结果造成印品网点糊死。这种现象首先可从辊子上的油墨膜的变化而觉察出来，一般是油墨膜变厚而且表面毛糙而无光。

2.原因：油墨乳化。油墨中的连结料尖掉携带颜料的性能，油鼍失去了流动性能后就变得短而成浆状，在辑子上看起来就像“死”的一样，结果是分配不良，传递性差。油墨中的连结料太稀，造成保护性差。油墨中所用的颜料抗水性差，分散不良，未完全润湿，比重大，吸油量小，颗粒粗而硬。油墨颜料含量太高。在多色印刷中，如果后印的油墨粘性太大，则就不可能套印上去很多油墨，结果就堆在橡皮布上。纸张上的涂层、纸粉、纸毛转移到橡皮布上后也会造成堆墨（堆橡皮布)。给墨量太多。油墨和水不平衡，水太多。水的酸性太大。

3解决办法：在油墨中加入一些适宜的稠连结料、蜡助剂、凡士林等以提高油墨的抗水性能。减少水量，降低水的酸性。减少给墨量。换用质量好的纸张。如果油墨的细度不好．则可以再分散之。选用合适的颜料(例如比重小的颜料)制造油墨。换用油墨。油墨中比重大的填料应尽量少用。

(四)印得太明锐(PrIntIng Too Sharp) 。

1.现象：印刷品的颜色越来越弱。

2.原因：油墨粘性太大。或为药水酸性太大腐蚀了版面，使之更亲水而疏墨。

3.解决办法：跟据不同原因，将油墨的粘性降低。或者降低药水的酸性。

(五)印版变色(Discoloration of The Ptata) 。

1.现象：印版的非图文部分（空白区）变暗。

2. Reason: The desiccant used in the ink contains too much lead, and as a result, a layer of lead phosphate film is formed on the plate, which is reduced to dark gray metallic lead.

3. Solution: treat it with dilute hydrochloric acid solution, and then apply glue (that is, wipe a layer of peach glue).

(6) Dry too fast (Drylng Too Fast).

1. Phenomenon: The oiler is in the ink fountain, on the blanket, and dried on the black silver.

2. Reason: There is too much desiccant in the ink. There are more low-volatility solvents such as ink oils in the oiler.

3. Solution: Add some anti-drying agent, or a small amount of castor oil and petroleum jelly to the ink. Replace with new ink.

(7) Drying Too Slow.

1. Phenomenon: The printed matter does not dry within the estimated time. Gets dirty easily. Feels wet and sticky to the touch and can stain fingers.

2. Reason: Insufficient desiccant in the ink, or the link material used in it is relatively slow to dry. The relative humidity in the printing room is too high. Paper is too acidic, and the pH value of non-coated paper is generally lower than 5.5, which affects drying. Paper humidity is too high. The potion is too acidic. If printing on non-absorbent substrates, inks containing high-boiling solvents that are not very volatile will result in delayed drying.

3. Solution: Add more desiccant to the ink, but it should be pointed out that if a lot of desiccant needs to be added to the ink, it is better not to use this ink, and use quick-drying ink instead. Adjust the relative humidity of the printing room to 60% or lower. It is better to use paper with a pH above 5.5, and it is better not to use a pH value lower than 5.5. Reduce water supply. Reduces the acidity of potions. Or add some cobalt acetate to the bucket. Alcohols such as isopropanol are added to the potion to reduce the amount of potion. Slow drying may also be due to lack of oxygen, so prints can be placed in a place with good air circulation. Inks used on absorbent substrates should never be used on non-absorbent substrates. Switch to fast-drying inks, which require only a small amount of desiccant.

(8) Emboss Ing The Blanket.

1. Phenomenon: the inked area on the blanket swells (dissolves) and bulges.

2. Reason: The blanket is not resistant to oil and solvents. Blankets swell after absorbing certain resins.

3. Solution: Wipe the blanket with an antioxidant solution. Treat the blanket with a sulfur solution (sulfur dissolved in carbon disulfide) to harden it before use. Switch to a synthetic blanket (such as one made from nitrile rubber). Replace ink. Change the solvent used in the ink.

(9) Filing of Roverse Type.

1. Phenomenon: The English letters on the big solid ground of the printing plate are blocked.

2. Reason: The ink film is too thick. too much stress. The printing performance of the ink is poor, and the graphics and text are spread or the place is dirty.

3. Solution: Use less ink, and use a thicker oiler to print thinner. Use ink with good fineness, excellent printing performance, and sharp printed lines. Appropriately reduce padding.

(10) Paper shedding or powdering (Flufflng).

1. Phenomenon: A single small fiber or a single small particle (filler) falls from the surface of the paper during printing, and they accumulate on the graphic of the blanket, resulting in a decline in printing quality. Although the crux of the matter was paper, printers always turned to oil makers for help.

2. Reason: The quality of the paper is too low. The printing speed is not suitable (too fast). The blanket is too stiff. Imprint force is too high. The amount of water on the printing plate is insufficient, and the average friction between the paper and the blanket is too high.

3. Solution: Use paper instead. The water supply should be adjusted appropriately. The printing pressure should also be adapted, not too large. Use a blanket with good elasticity. Use a blanket that is less ink-absorbent and solvent-resistant. Use a smooth, flat surface blanket. Use inks that are as viscous as possible so that the ink film breaks easily during imprinting. Reduce the printing speed, the degree of powder loss is almost proportional to the printing speed. Wash blankets and printing plates in time.

(11) Ghosting ln Solid Areas (Ghosting ln Solid Areas).

1. Phenomenon: There are small, piece-by-piece slight imprints on the field. The BI image is vaguely repeated elsewhere.

2. Reason: Due to poor ink distribution, there is insufficient ink in some parts. It is easy to appear when the printing is solid and low (or the design with relatively dense graphics), because this also takes away part of the ink from the ink roller. Repeated embossing on the plate. The ink is too soft and too short. Transparent ink is more serious than opaque ink. Polished (or oxidized) ink has poor ink transfer. Silver installation is not necessary, resulting in poor ink transfer and distribution.

3. Solution: Make the solid plate well distributed, and put the solid pattern part of the plate on the side of the mouth as much as possible. Reduce the water supply, as this will make the ink shorter and less viscous, resulting in poor ink distribution. Use long, viscous and fluid oil cum. Use ink with little transparency. Switch the jaws of the plate to the other side. Use additional form rollers, distribution rollers , or replace the diameter of the form rollers . If possible, increase the serial movement between the rollers .

(12) Graphic and text thin lines disappear (lmage DetailDlsappears).

1-Phenomenon: The subtle layers in the printed matter disappear, and the printed matter looks weak and streaked.

2 reasons: the ink is hydrophilic. The potion is too acidic. Too much water is being given.

3 Solution: Use ink with good performance and mature ink after storage. In the ink, a good water-resistant binder should be used. Add some unsaturated fatty acids in oil. Reduces the acidity of potions and reduces the amount of water given.

(13) Thickening of pictures and texts (lmage Thlckens).

1. Phenomenon: The dots and lines of the printed matter become wider and larger, and the printed matter looks oily (fatty).

2. Reason: The ink is too thin and too oily. The acid value of the binder in the ink is too high. The oiler is too water resistant. Unsuitable waxes or fats in oil ounces. Poor dispersion of oil plastic. The potion is too acidic.

3. Solution: add some sticky linking material to the ink. Check whether the dispersion fineness of the ink is qualified. Increases the acidity of potions. Increase water supply. When making ink, a link material with a relatively low acid value should be used. There must not be any lipids in the ink formulation.

(14) No ink (also known as Motuo series Ink Retreating From FountainRoller).

1. Phenomenon: Streaks appear on the printed matter, and the hue is relatively light.

2. Reason: The ink yield value is too high. The oil is too short to be cheese-like. The pigment content in oil emerald is too high. The ink has gelled or water has entered the bunk causing partial flocculation.

3. Solution: Stir the ink in the ink fountain constantly. A stirrer is installed in the ink fountain. Or put an iron rod on the ink in the ink fountain to push the ink to the ink fountain roller to keep the ink flowing. Adjust the ink with medium and high viscosity vehicles. Use ink with good fluidity and strong water resistance.

(15) Spots (Mottlo).

1. Phenomenon: the color of the printed matter is inconsistent, some are light, some are dark, especially the solid prints, the stains are quickly formed, some of these stains are irregular, and some are regular.

2. Reason: Flat printing spots are roughly similar to embossed spots. The surface of the paper is irregular and the ink is too transparent. If the printing pressure is too high, there will be a sense of extrusion. When the ink is pressed into the concave part of the paper surface, the ink film on the convex part will be squeezed out. The performance is that the ink film on the concave part of the paper is thicker, while the ink film on the convex part is thinner. , if the transparency of the ink is good, this phenomenon is more prominent. If the water is too large, or the ink emulsifies too quickly, the viscosity of the ink will decrease and it will be squeezed out more easily, resulting in unclear and uneven printing. If the colored water drops fall on the solid position of the printing plate, it will form Snow flakes.

3. Solution: Use thicker ink and lower pressure. The water resistance of the ink is better, and the fluidity and distribution performance of the oil film cannot be affected after entering the water. Use opaque inks whenever possible. Replace with good paper with an even surface.

(16) Rogister Incorrect.

1. Phenomenon: Multi-color overprinting is not allowed.

2. Reason: paper moisture absorption deformation elongation or lack of mechanical strength. Improper, inaccurate plate and blanket pads. Blanket swells and bulges. The blanket deforms due to pressure. Photoengraving is inaccurate.

3. Solution: Put the paper under the relative humidity which is 5~10% higher than the printing room. Check the flatness of the roller pads. The length of the printed matter can be increased by removing the pad under the printing plate and placing it under the blanket. On the contrary, taking out the pad under the blanket and placing it under the plate library can reduce the length of the printed matter. Replace with a good quality blanket. Measure the length of the first color and replace with a good printing plate.

(17) The ink becomes spotty drying (Spotty Ink Drying).

1. Phenomenon: This situation often occurs when most of the printed matter can be wiped off (except for the hard dry film in different parts). Of course, this situation generally occurs at the edge of the printed matter, and a small part of the ink can be wiped off.

2. Reason: At the beginning of oxidative drying, the drying center (or core) is formed first, and then gradually spreads outward to dry. A poorly dried film will not spread out well.

3. Solution: Add slurry desiccant to the ink. Using a new type of quick-drying ink. Check the storage time of the ink, some black inks have the problem of a little drying after long-term storage.

(18) Weak Solid.

1. Phenomenon: The printed matter on the ground is dull and flake-like.

2. Reason: Improper handling of the desensitivity of the printing plate, wipe the printing plate with excessive water. The paper does not absorb enough moisture, and the liquid medicine gathers into drops, which affects the leveling of the ink.

3. Solution: The printing plate must have a good desensitization (grease) property. Use stronger inks. Some wetting agents can be tested in the potion to increase the ratio of absorption into the paper. Increase the amount of ink supplied.