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Showing posts from August, 2020

How To Make Printing Ink

  Introduction Printing ink is so much more than just the black stuff that you put on a page. It has been around for thousands of years, and it's been used in everything from newspaper presses to digital printers. As you can see, we're not talking about offset printing ink which is oil based. I want to have a little fun and talk about how you can make your own ink for your printer.  At home! Ready? Ingredients You will need the following ingredients: Soot (5 tbsp) : This is as purest as it gest. You can make the soot yourself by holding a glass up to a flame. This will allow you to slowly accumulate the soot. Water (2 tbsp): For the base of your ink, use distilled water so that you don't introduce any impurities into the mix. Distilled water is also easier to clean up than tap water because there are no minerals or residue left behind from tap water. Alcohol (2 tbsp) (grain alcohol): This ingredient works as a preservative for your ink and allows it to last for several mo

Calender Cuts - Troubleshooting Paper Defects

What do they look like? Calender cuts are relatively small wrinkles, usually 5 to 8 centimeters long that run at a slight angle to the grain direction of the paper. These wrinkles are compressed to the point that they make an actual cut in the paper.  However not all calender cuts actually cut the paper. How do they happen? As the paper is being made, it passes through the paper making machine and loses moisture.  Near the end of the machine, when it is almost complete, it passes through what is called a super calendering process.   Calendering means that the paper is squeezed through a series of steel rollers to make it the proper caliper and basis weight.  The pressure is so great that any imperfections can cause cuts in the paper. If the paper has a poor profile before entering this squeeze, excess paper will crease when it passes the nip point.  Foreign objects like fibers or hairs can cause hair cuts.  But a calender cut is not a foreign object.  It is a wrinkle.  The pressure is

Uneven Paper Winding - Troubleshooting Paper Defects

  This is an uneven winding of the paper reel at the mill.  If the roll was at the end of the jumbo reel, the web was winding in an out during the process. Both the lateral movement of the sheet or core can cause this.  Problems that this causes on a web offset press: Automatic lateral adjustments of the web guides will not function properly as the edge of the paper changes. The edge of the paper will wander to offset blanket's inked edges of the paper that are out of print. This can cause web breaks.  The finished product will have uneven edges of the newspaper or magazine.

Slack Start - Troubleshooting Paper Defects

A slack start is the cause of paper wrinkling near the beginning of the core of a paper roll.  Web offset printers will usually splice off early to avoid these defect wrinkles.  However these wrinkles can extend part way into the roll and results in distorted print or even web breaks. How does this defect happen? Paper machine companies begin a new roll called a jumbo when starting a new paper roll.  These rolls rely and a tight start at the core.  When this doesn't happen, the first few winds can have wrinkles. Paper roll jumbo on paper machine. Paper manufacturers will make some kind of disclaimer that their rolls are usable only at a certain distance from the core.  If this paper defect goes beyond this, a complaint or even a claim can be made by the offset printer against the paper company. To be safe, it is best to establish a buffer amount and to splice off slightly early on each roll. 

Edge Cracks - Troubleshooting Paper Defects

  Edge cracks are caused at the paper mill by the slitter when slitting rolls to size for offset web printers.  The result is small cracks, or tears no longer than an inch that appear randomly on the edges of a paper reel.  They are usually closer to the core. What causes edge cracks? There are two causes.  The first is due to uneven paper caliper and strength.  The second is that the setting of the slitter at the paper mill. The slitter is set too deep or too shallow against the cutting anvil.  In the case of edge cracks, if the slitter is too deep, it will cause a sawing effect.  Combined with tension it will cause slight tears, or edge cracks.   The same principle applies to running a slitter on a web press.  Here are the optimum depths and angles to run a slitter for paper. The optimum depth of a slitter against an anvil is .06" for paper.  But this can depend on the type of paper being slit.  Anything outside of this range will cause edge cuts. How to detect edge cracks on pr

Paper Burst - Troubleshooting Paper Defects

  A paper burst is a tear, usually greater than 3 inches, that occurs anywhere other than the edges of a roll or sheet.   These tears are caused by tension during the paper making process. The tear is actually a rupture caused by too much tension between hard and soft sections of the paper reel during winding. The high tension exceeds the strength of the paper as it is winding and tears.   The tears happen at irregular intervals in a sheet pile or paper roll. They are most common on the outer diameter. They form a somewhat curved split in the paper and they almost certainly cause paper jams for offset sheetfed printers and web breaks for web printers. 

Winder Wrinkles - Troubleshooting Paper Defects

  Winder, or crepe wrinkles, happen during the winding process at the paper mill. They are no more than a 1/4 inch wide.  They form a weakness in the paper and lead to jams in the delivery process.  They also disfigure type and pictures during the offset printing process. How do they happen? Winder wrinkles are the result of poor tension during the winding process. If the outer layer of a paper wind is tighter than the one on the inside, or the paper caliper varies in any way, these wrinkles will form. This is exacerbated by the fact that the slippage between the paper layers is blocked.  They can appear in multiples and repeat along the length of the sheet or web.  Offset printers will find this paper defect in all places in a paper roll or sheet pile.  In paper rolls, it will most often be found near the beginning or end of a paper roll. 

Slivers and Shives - Troubleshooting Paper Defects

A shive or sliver is a small bundle of fibers that were not properly broken down by the chemical pulping process when making paper. Both looks similar, but the cause is slightly different. Shive - This describes a small piece of wood in the paper making process that has been cooked, but the fibers did not break down and separate properly. Most shives are separated in the screening process but not all. They are difficult to identify because they have been bleached in the chemical process. Sliver - This describes small splinters of wood will not get cooked properly and make their way into the sheet.  It is easily seen in the paper and is a long fibrous defect that is more easily seen. Both slivers and shives causes web breaks for web offset printers.  Each of these defects cause a weakness, or even a slight cut in the paper.  When put under tension, these will cause breaks.  Especially when the defect is at the edge of the paper. What shives they look like While the above picture shows

Hair Cuts - Troubleshooting Paper Defects

A hair cut is a smooth, sharp cut in the paper that is too uniform to be a tear.  It is caused by foreign materials inside the pulp during the paper making process. Such foreign materials could be a hair or other synthetic materials such as from brushes.  The actual cut does not take place until the paper reaches the super calendering part of the paper making process.  Super calendering is when the paper passes one of it's final stages and is compressed between metal rollers to get it's thickness and establish it's basis weight. Super calendering rollers. This involves multiple passes through rollers to get compressed to the proper thickness. When the paper is compressed to it's point of final thickness, any hairs or similar foreign objects will form a "cut" in the paper.  This looks like a long, smooth line that is sharply defined. Hair cut. A hair cut paper defect has a smooth and defined path. There is no definite direction or length to a hair cut.   They a

Slime Hole - Troubleshooting Paper Defects

A slime hole occurs early on in the paper making process when bacteria forms a slimy substance . White water (water that has 4% paper fibers) is then poured over a wire mesh which catches the fibers. The bacterial slime then deposits on to a wire and a hole in the paper develops. Where do slime holes form? In the paper making process, a wire mesh, or a fourdrinier table receives diluted water and paper.  At this point the mixture is extremely diluted, only 4% pulp and 96% water. See the video of a fourdrinier table below. Water is poured onto this table and occasionally a slimy bacterial droplet can form.  The paper fibers will not settle properly and the outline of a hole, or actual hole will form. This hole makes it's way through the paper machine and dries. The bacteria then die which leaves an opening with hard crusty edges. Sometimes it will break, other times it will make it through. Photos of slime hole forming in paper machine. Where a slime hole is discovered. If the slime

Pick-out or Plucking Hole- Troubleshooting Paper Defects

A pickout or plucking hole is a paper defect that happens in the  paper making process.  It is similar to a slime or water drop hole, therefore identifying it requires another approach. There are several causes of holes forming in a paper machine.   1. Equipment defects. 2. Bacterial slime in the pulp. 3. Sticky material on the rollers The third reason is the cause of a pick-out or plucking hole.  As the roller rotates, dust or a buildup of paper fiber sticks to the web of roller and causes a continuous hole at regular intervals.  Below is a close up of a roller inside a paper machine. If any dusty or fibers collect on a spot in the roller, it will cause a puncture in the paper at regular intervals. How to identify this defect The only way to identify this paper defect is by finding it at regular intervals in the stack of sheets or paper roll.  The diameter of the roll in the paper machine will determine the distance between the holes. Some rollers are quite large and may have long int

Water Drop Hole - Troubleshooting Paper Defects

A water hole paper defect happens at the paper mill during the manufacturing process.  Because of the high humidity, water droplets sometimes form and drop onto the web of paper.  A hole will form and it will be seen in the sheet or web.   Offset printers sometimes mistaken these holes for a slime hole.  However a water drop hole is distinctly different.   The difference between a slime hole and water drop hole. Notice the picture above on the left hand side.  It is a hole, but has discolored edges.  The bacterial slime has caused these outer edges of the hole to have this distinct look. Now look at the hole on the right.  This is a water drop hole.  They are generally very small and do not have the decayed and discolored look on the edges.   Paper machines have cameras placed throughout.  These cameras are designed to find such water drop holes and take pictures of them for troubleshooting.  Here are some pictures. To a paper mill, identifying this paper defect makes a world of differ

Starred Reel - Troubleshooting Paper Defects

A starred paper roll is defined as a reel that is not uniformly wound.  The outer diameter of the roll was wound more tightly than the inner core.  This results in depressions at various points in the reel. It a non-uniform wind. How it happens. From time to time the paper mill must make a splice in a reel due to paper breaks or other running issues.  Or the operator simply makes an adjustment in tension.  When the paper machine begins again, the tension can be inconsistent.  This will result in the inside layers buckling underneath the pressure of the lower layers. The problem is exacerbated by handling.  Clamp trucks or storage methods will cause more starring in the wind of the roll.   This is distinguishable from the paper defect considered an out of round roll.  The difference is that the problem occurs around the entire diameter of the roll.  This is now a tension issue from the mill and is considered a starred reel. Can these rolls be used? Yes, but expect variations in tension

Roll Out of Round - Troubleshooting Paper Defects

By definition this paper defect occurs when the diameter of a web press paper roll is not uniform.  The roll diameter will show different measurements depending on where the measurement is taken. An out of round roll can have several causes.  Here are a few: 1. The roll sustained a hard impact during the transportation process. 2. It was stored for an extended period of time with weight on it. 3. Excessive clamp truck pressure. 4. Loosely wound roll from the paper mill. Problems caused on an offset web printing press: 1. Roll stand will bounce. 2. Web tension can fluctuate as the roll wobbles. 3. Doubling in the printing units. 4. Web breaks. Out of round rolls often show waviness. The best way to prevent this type of paper defect is through proper storage and handling.  Care must be taken when handling the rolls.  Clamp pressure must be set according to specifications outlined by the paper company.  Storage mush also be such that paper rolls are stored on their side. On an offset web