Ghosting
Over the years, APR has shared many articles that assist in identifying and reaction to print defects such as dirty print, ink spitting, and ghosting. But as technology, equipment, and operating techniques develop, we find it necessary to revisit these areas of concern that continue to challenge many of us on a daily basis. As I look back and think about my experiences with certain pressroom challenges I often remember the first time and place I was faced with a particular challenge. As I trained as a young press operator in 1982, my only exposure to a flexo inking system was a four roll inking system. The press had a metering roll partially submerged in the ink pan, which transferred the ink to an anilox roll; and from what I recall there was never a shortage of ink delivered from plate to substrate. But then again, who knows...I’d never heard of solid ink density and the term “ghosting” had no meaning to me whatsoever. But also introduced to flexo in the 1980’s was a component now commonly known as the (ECDB) enclosed doctor blade system. This unit can be credited with contributing to both better print quality, higher press speeds, and reducing ink consumption. It was also with my introduction to this new component that I had my first experience with ghosting. In Part 1 of this series our primary focus will be on “ghosting”.
What is Ghosting?
The flexographic term ghosting is actually borrowed from the offset printing industry. Mechanical pinholing is the print defect that we have adopted the term ghosting for in flexo. However, it does seem that most of us are in agreement that “ghosting” can be described as a faint image, which is repeated from another part of the design and appears in an area where it is not intended to be in the flexo print process. This type of ghosting is always found in the image area on the printed side of the substrate and most noticeably in large solid areas. Ghosting became more common after the advent of chambered doctor blades.
What Causes Ghosting?
In most cases ghosting occurs when the anilox roll cannot recover enough ink to consistently provide the required ink density. Ghosting problems are not necessarily more prevalent in darker colors, but they are certainly more apparent in darker colors like browns, reds, blues, and greens. The idea behind eliminating or reducing ghosting is to improve the ability of the anilox cells to both fill with and transfer ink.
Giving Up The Ghost
Both the porosity of an anilox roll’s cell walls and the cell depth greatly affect the transfer of ink to the substrate. As press speeds increase, the ability to consistently and effectively fill the cells on the anilox with ink in order to deliver a uniform ink film thickness to the plate becomes more challenging. The cell depth-to-opening ratio is of critical importance. Deeper cells may mean greater volume. However, if the surface tension of the printing plate is too low to pull the like particles of ink from the cell, then transfer will be very poor and ghosting may occur. Likewise, if the surface tension of the anilox roll is too high, it may easily pick up the ink from the fountain roll or the chamber, but not release ink from the cells resulting in ghosting. Because of the anilox roll surface topology, it is nearly impossible to accurately measure the surface energy or dyne. However, it is possible to test the transfer rates of printing plates with a large dyne range. In addition, proper ink viscosity is also important in reducing ghosting whether you are using solvent, UV or water-based inks.
Possible steps to minimize ghosting problems include:
- On colors where ghosting is occurring, change the anilox roll to one with the same cell volume but with a coarser screen. This will bring the same amount of ink to the plate but with reduced ink drying on the anilox as long as the ink transfer rate is comparable.
- With solvent inks and sometimes water-based ink, the viscosity may be too low. A higher viscosity should slow ink drying on the anilox rolls.
- Because the defect is normally seen in large solids with reverse print or windows, you will sometimes have an overprinting white (reverse print on clear substrate). In this case the white can re-wet the ink that the ghosting occurs. So speeding up the white ink could yield favorable results.
- If possible, put ghosting color on a back deck to utilize the full chamber for wetting.
- Make sure the anilox is covered and protected from ambient air or air blown from the BC (between color) dryers.
- Reduce blade pressure, which will reduce friction and heat at the sheer point of the ink.
- Some enclosed chamber systems utilize an isometric inner cavity contour that through the use of fluid dynamics fill each cell with ink, and remove the air from the unfilled cells returning it to the feed tank for dispersal into the atmosphere. This process helps prevent ghosting and starvation from occurring, due to air pockets or foam build-up in the ink.
- If possible, try to increase the dwell time between blades or run trouble inks on decks that have enclosed systems with greater openings. This will assist in the rewetting of ink on the anilox roll. A deeper chamber cavity will also reduce agitation inside the chamber, minimizing air pockets that could result in either ink starvation or ghosting. An analogy that always comes to mind is that Lake Erie is both the shallowest and most turbulent of all the Great Lakes, whereas Lake Superior is the deepest and calmest.
- Severe ghosting can sometimes be reduced by adding extender or using a solution of 10% normal propyl acetate/90% ethyl alcohol.
- While never the most popular action to take in a production environment, reducing the press speed can also reduce this effect.
- Another solution, while not very practical, would be using a specialized anilox roll for a problematic job. If the anilox roll is the same diameter as the print cylinder, or at least a factor of the print repeat, it will synchronize with the design and ghosting will not appear. This would mean the cfd (complete finished diameter) of the anilox would be the same or a factor of the cfd of the print cylinder/print sleeve (consisting of bare cylinder diameter + the sandwich, i.e. mounting tape, plate, and possibly sleeve).
Other Potential Causes
Another phenomenon, which can be mistaken as ghosting or even ink setoff, can occur when running a 100% lacquer coat in the last-down deck, especially on paper substrates. Ink setoff occurs as ink transfers to the reverse side of the substrate on top of the printed image. Often the lacquer roller impression is hitting too hard, so it picks the printed image and duplicates this image. Unlike true ghosting, this can occur in either the printed or non-print area of the printed side of the substrate. This is often caused by four things:
- The operator has over impression on the rubber roller.
- The rubber roller has low spots and needs to be reground or replaced with a new one.
- The viscosity is way too high causing the over lacquer to be tacky and “pick“ the image, thus duplicating it.
- The print cylinder gear is the wrong size.
You can read the entire 3-part series here:
Understanding Common Flexo Print Defects — Part 1 — Ghosting
Understanding Common Flexo Print Defects — Part 2 — Dirty Print
Understanding Common Flexo Print Defects — Part 3 — Ink Spitting
APR Technical Solutions Group
We have formed our Technical Solutions Group to encompass our full range of expertise in all critical areas of the flexo process. This team is made up of industry professionals dedicated to being up to date on new technologies, armed with the last in diagnostic tools, and experienced in problem solving that can achieve sustainable results. The TSG have walked in your shoes, and has felt your pain. For any specific questions please feel free to contact me at 847-922-0134 or
For more information, call us at 1-800-445-4017, or fill out the Information Request Form.
FAQs
What is flexographic printing PDF? ›
Flexographic printing is a common printing method in the packaging field. The printing method is characterized primarily by the flexible printing plate and the low viscosity inks which make it suitable for use on almost any substrate.
How does flexography work step by step? ›Before moving on to the next station with the next color each ink transfer must line up exactly in
What is flexography printing most commonly used for? ›Flexography is a roll-feed web printing process. Flexographic printing is commonly used to print high volumes of labels and packaging. Presses can print on a variety of films, foils, papers, corrugated board, and paperboard and achieve speeds of 500 to 2000 feet per minute.
How can I solve printer problems? ›- Check to make sure the printer is turned on and connected to the same Wi-Fi network as your device. ...
- Unplug and restart your printer. ...
- Set your printer as the default printer. ...
- Clear the print queue. ...
- Reset the service that manages the printing queue.
Common factors include driver problems, software issues, hardware failures and overuse.
What type of ink is used in flexo printing? ›Flexographic printing is done on paper, cardboard, or plastic film. Liquid inks with a low viscosity are used for printing. There are water-based inks, solvent, and ultraviolet (UV)-cured inks among them.
What is LPI in flexo plate? ›Line screen is typically measured in LPI or line per inch. This variable indicates how many micro dots are found per inch on your plate. One can think of LPI as in pixels of a computer screen. The higher the line count, the higher the pixels. Therefore, the higher the LPI, the higher the resolution of the print.
What is reverse printing in flexo? ›The reverse printing is widely used to produce the printed packages for Snack, Juice, biscuits, Ketchup,,,, etc. , in this technique the ink is printed on the inner layer of substrate and it do not become in direct contact with human skin, weather conditions and other substrates because in most of cases the ink is ...
How many types of flexographic presses are there? ›There are three types of flexo presses—central impression (CI), inline, and stack. The configuration or mechanical build of each is what sets them apart physically. This influences why certain substrates are run on one type of press over another, as well as common applications produced.
Why is it called flexographic printing? ›flexography, form of rotary printing in which ink is applied to various surfaces by means of flexible rubber (or other elastomeric) printing plates.
What materials are used in flexography? ›
- Paper.
- Plastic film.
- Corrugated cardboard.
- Non-woven fabric.
- Metallic surfaces.
- Multilayered film composites.
- Versatility. ...
- Wide variety of inks. ...
- Performance. ...
- High quality image reproduction. ...
- Low production cost. ...
- Eco-sustainability. ...
- Optimize the printing process of hygiene products.
Originally, flexo plates were made from rubber, but are today made from photopolymer material in sheet form – which differentiates them from the fixed metallic printing plates of offset printing. The plates are flexible enough to be wrapped around cylindrical print/plate rollers.
What causes error printing? ›The “Error Printing” message is generally caused by a loose connection or outdated printer drivers. When this dialog box appears on your screen, it could be accompanied by an error code for reference or no code. Do not confuse this issue with the Missing or Damaged ink cartridge errors.
How do I clean printer heads? ›How To Clean Printheads - YouTube
What are the quality issues in design for print? ›- Colour Imbalance. The translation of the colours you see on the screen to those your printer produces is a complex and approximate process. ...
- Haloing. ...
- Feathering. ...
- Print Swathe Misalignment. ...
- Striping Or Banding. ...
- Restricted Colour Gamut. ...
- Poor Greyscale Range.
My printer won't print
Make sure there is paper in the tray(s), check the ink or toner cartridges aren't empty, the USB cable is plugged in or the printer is connected to Wi-Fi. And if it is a network or wireless printer, try using a USB cable instead.
Inkjet printers. Inkjet printers are the de-facto standard for consumer/home-use printers. They're inexpensive and use liquid ink that is relatively inexpensive to replace. They can produce high-quality color printing or fairly fast monochrome (aka B&W) prints.
How the viscosity of flexography inks are measured? ›Ink viscosity can be measured in two ways, manually or automatically. Manual measurement is the most common in the flexographic industry, using gravimetric analysis, submergence, or cups, called flow cups. Automatic measurements are made with viscometers that are attached to the machines.
Why is the anilox roller so important? ›The Anilox Roller is often referred to as the heart of the flexographic press. It is designed to deliver a precise and consistent amount of ink to the printing plate.
Why the liquid inks are used for flexographic process? ›
The principal reason for this is that flexographic printing uses less ink than gravure printing, meaning that even when water-based inks—which dry more slowly than solvent-based inks—are used, drying requires little energy, facilitating superior productivity, i.e., high-speed printing.
How is LPI calculated? ›Calculate lines-per-inch using the following formula(s): LPI = number of Lines to be printed on a page / printable height in inches, or. LPI = lines per page / paper height - (top margin + bottom margin)
What is the difference between LPI and DPI? ›DPI – Dots Per Inch –the resolution of a printed image, how many tiny dots of ink printed per inch. The more dots, the finer the print. LPI – Lines Per Inch – refers to the lines of in a halftone or screen - the higher the number, the smaller the screen.
What is anilox volume? ›Anilox volume refers to the carrying capacity of an anilox cell, or the amount of ink held in each cell, during Flexographic Printing. It is one of the many factors that determine the amount of ink that is transferred to the print material and therefore has to be accurately controlled and measured.
What is offset printing process? ›offset printing, also called offset lithography, or litho-offset, in commercial printing, widely used printing technique in which the inked image on a printing plate is printed on a rubber cylinder and then transferred (i.e., offset) to paper or other material.
How do you print in reverse order? ›Printers usually print the first page first, and the last page last, so the pages end up in reverse order when you pick them up. To reverse the order: Press the menu button in the top-right corner of the window and press the Print button. In the General tab of the Print window under Copies, check Reverse.
What is the difference between flexo and offset printing? ›The main difference with both processes is that offset printing is only done on flat surface while Flexographic printing can be used on almost any substrate with a flexible surface.
What are the advantages and disadvantages of flexography? ›Advantages and disadvantages of flexography
Flexography is a very cost-efficient printing process. Compared to other printing methods, flexography uses low-cost materials, making the printing process a lot cheaper. Flexography allows high speed printing. Hundreds of meters of printing can be done in only one meter.
A doctor blade is used to shave excess ink from the surface leaving just the measured amount of ink in the cells. The roll then rotates to make contact with the flexographic printing plate which receives the ink from the cells for transfer to the printed material.
What is flexographic design? ›Often referred to as flexography or flexo, it is essentially a modern version of letterpress printing, and can be used for printing on almost any type of material, including plastic, metallic films, cellophane, and paper.
Does flexo use CMYK? ›
Flexo print vs Rotogravure
They can both use CMYK and Pantone colours in the printing process, but they do normally use Pantone colours.
digital printing” conversation relies on run size and cost as the deciding factors, and goes something like this: Flexographic printing requires more setup time, and each change in graphics (e.g., flavor variations, varietals, etc.) requires new plates to be made.
What does flexo mean? ›(ˈflɛksəʊ) n, adj, adv. (Printing, Lithography & Bookbinding) short for flexography, flexographic or flexographically.
What was the first type of printing plate used in flexography? ›In the early 1900s, the process evolved into “Analine Printing,” which utilized rubber printing plates and analine oil-based ink. The presses were primarily made in Germany where the process was referred to as “Gummidruck.” Modern flexographic printing is still often referred by its predecessor's name in Germany.
Is the major component in flexography printing press? ›Key Components For Ink Distribution
In modern flexo systems only one or two rollers are involved with the actual distribution of ink during flexographic process: the fountain roller and the anilox roller. The fountain roller is responsible for transferring the ink from the ink pan in the machine to the anilox roller.
A flexo press operator job requires you to manage flexographic printing press machines that can print on all sorts of surfaces like fabrics, paper, and plastic bags. You usually prepare the press for printing, feed the textiles or paper into the machine, and troubleshoot any issues during printing.
What are the disadvantages of flexography printing? ›- It can be complex: flexography printing equipment can be complicated. ...
- Plates can be expensive: the most important part are the printing plates and if you are needing several colours, you will need to provide a plate for each.
Flexographic printing, or Flexo, is a technique for bulk printing using flexible relief plates. The manufacturer applies the ink first on the plate and then on the surface. This is a low-cost printing method, and it has progressed much since 1970 after direct laser engraving was introduced.
What are the advantages and disadvantages of offset printing? ›- Pro: Ideal for large or commercial-scale print runs with a need for consistency.
- Con: High turnover times associated with complicated set-up.
- Con: Edits and proofing are time-consuming and costly.
Cyrel® Coating & Varnish Plates are developed to provide a solution for printers and converters using varnishing and special effect ink and coatings applications.
What is photopolymer plate? ›
Simply put, a photopolymer plate is a sheet of polymer with one side that is light sensitive. The digitally created design is transferred to a photo negative that is placed on top of the sheet of polymer. It is then exposed to light in a controlled exposing unit.
What are the various defects found in dyed and printed fabrics? ›- BARRE. Fabric will appear to have horizontal streaks. ...
- COLOR BLEEDING. It's a loss of color when the dyed fabric is wetted or immersed in water. ...
- COLOR CROCKING. ...
- OFF SHADE. ...
- SHADE BAR. ...
- SHADE CROSS BAR. ...
- CREASE STREAK. ...
- DYE STREAK IN PRINTING.
Textile printing is one kind of localized dyeing where dyes or pigments & chemical applied by any method which can produce a particular effect of color on fabric according to design.
What are the defects arising from dyeing faults? ›Moire effect. Shade change from selvedge to selvedge. Shrinkage/distortion. Creasing/chafe marks.
What are the common problem in reactive dyeing? ›Reactive dyes are highly preferred for cotton for their excellent fastness properties and easy application. But the problem in reactive dyeing is the low exhaustion properties due to the hydrolysis of reactive dyes with water.
How many types of fabric defects are there? ›| Sr. no. | Defect Name | Appearance |
|---|---|---|
| 1 | Crack | Too few picks per inch in a certain area. |
| 2 | Float | Distortion of in weft direction generally accompanies with warp break |
| 3 | Wrong Drawing | Irregular pattern warp way in the cloth. |
| 4 | Leno Problem | Leno end not holding correctly |
4 Major defects -> 1 critical defect -> stop the production. Minor Defect – A defect that does not reduce the usability of the product but is nevertheless a workmanship defect beyond the defined specifications or construction requirements.
What is 4 point system in fabric inspection? ›The 4-Point System assigns 1, 2, 3 and 4 penalty points according to the size, quality, and significance of the defect. No more than 4 penalty points is assigned for any single flaw. A defect can be measured either length or width direction; the system remains the same. Only major errors are considered.
What is ghosting in printing? ›Ghosting is the faint image produced during flexo printing that you can see on large, solid areas. It's mostly a result of the anilox failing to consistently or completely recover adequate ink densities, also known as a failure to properly rewet the cells.
What is an offset printing error? ›Posted on 2/15/2022. This error involves a mirror image of the design on the other side of the note. Paper Money Guaranty® (PMG®) is the world's leading authority on banknote errors, a popular segment of numismatics.
What is offset printing process? ›
offset printing, also called offset lithography, or litho-offset, in commercial printing, widely used printing technique in which the inked image on a printing plate is printed on a rubber cylinder and then transferred (i.e., offset) to paper or other material.
What defect means? ›: something or a lack of something that results in incompleteness, inadequacy, or imperfection: as. a : a flaw in something (as a product) especially that creates an unreasonable risk of harm in its normal use — see also latent defect.
What is slub defect? ›Slub refers to thick or heavy places in the yarn or flying waste yarn getting into yarn feeds during the spinning process. Slub and other inconsistencies are common in fabrics produced on vintage shuttle looms. Major or Minor. Smash. Small caused by a number of ruptured warp ends that has been repaired.
What is reed mark? ›Definition of reed mark
: a warp mark in cloth caused by defective reeds or a faulty setting of the loom or yarns.