By Olivia Cahoon
UV ink’s chemistry combined with the ability to cure quickly when paired with LED lights enables printing onto substrates like glass, leather, metal, stone, and wood. The surfaces of these untraditional materials are clear, brown, or gray and may require white ink.
White ink is a great way to stand out from the competition by offering a highly valued product. However, print service providers (PSPs) should consider the added costs of using white ink, including liter prices compared to CMYK, as well as maintenance and ink layering. The composition of white ink also requires preventative measures to avoid clogging.
Designing and printing an application that uses white ink is another consideration. The process may not be as straightforward as CMYK and require opacity testing as well as first or second surface printing. PSPs can plan appropriately by looking at the application, layering techniques, and lighting conditions.
Above: White ink allows for printing onto surfaces like wood, as shown in the photo of a table from Ricoh.
White Ink as a Consumable
Utilizing white ink often plays a role in producing high-profit graphics. However, this specialty feature does come at an added cost not only in terms of price per liter, but also from ink layering and opacity requirements.
As a consumable, the price of white ink compared to CMYK depends on print method, equipment, and the level of output from the press, shares Becky McConnell, segment marketing manager, wide format inkjet, Fujifilm North America Corporation, Graphic Systems Division. Digital printers with high-production capabilities typically allow for white ink prices closer to CMYK compared to entry-level devices.
White ink’s price per liter varies considerably, but on average it’s ten to 15 percent more expensive than CMYK. Some companies address price by offering short fills. “For example, if they generally sell 1,000 milliliter of CMYK ink, they’ll sell an 850 milliliter container of white for the same price—while others standardize on volume and adjust the price,” explains Mark Manning, senior portfolio manager, commercial printing group, Ricoh USA, Inc.
Pricing per liter is not the only cost consideration for using white ink. Print providers also need to look at how much white ink is used per job compared to CMYK, which depends on the application. Randy Paar, marketing manager, display graphics, Canon Solutions America, offers, “since white can be used in so many ways—single or double channel white plus single or double layer printing, it is really application dependent.”
For example, McConnell says jobs with a spot white on a dark or metallic substrate may use very low white ink compared to a flood white layer, which could use twice as much ink as a CMYK layer. For wide format digital inkjet, the white ink’s drop size contributes to how much white ink is used. “Larger drops of ink naturally lay down a larger amount of ink, so that plays a role in how much is needed and the cost to print.”
White ink is not used on every job, but it is used for specific reasons. The amount utilized depends on the design and how/where white ink is placed. Jay Roberts, product manager, UV printers, Roland DGA Corporation, usually sees the majority of white ink usage on black and clear substrates. “There was a definite increase in white ink use—about 30 percent—over the years.”
The amount of white ink used also depends on desired opacity. According to Jason Darrah, chief inkjet evangelist, Fluid Color LLC, more white ink is required to create a thicker ink film that increases opacity. Due to the layering of white to create opacity, the cost when printing white is greater than just printing CMYK. Additionally, most applications use roughly three times as much white ink as CMYK to achieve desired opacity.
To ensure the bottom line isn’t negatively impacted, print providers should factor the cost of white ink into their selling price. To help with this, Paar says Canon Solutions America recently released Océ PrintSight, which accurately tracks ink usage per color and job.
Print providers should also consider the application possibilities that white ink enables. For example, white ink allows printing on clear substrates like acrylic, a typically high-profit application. It also enables second surface printing like floor graphics with a white layer on top. “And with wide format digital production, print providers can print a high-profit one-off piece for a high-end customer like a local museum,” adds McConnell.
Recirculation Is Integral
White ink’s composition means it needs constant recirculation to prevent clogging. This maintenance also contributes to white ink’s higher costs when compared to CMYK.
White ink is made with titanium dioxide—a pigment with a density of 4 g/cm3, four times the density of the binder in which it is suspended. For this reason, white ink tends to settle over time to the bottom of containers, lines, and printheads. When left untreated it can lead to clogging and the white color becomes lighter.
Recirculation helps keep the ink in agitation and benefits the suspension of the pigment. Pedro J. Martinez, CEO, Afford Industrial, shares, “although we may think that shaking the bottle is enough, when the printer is quiet the pigment may deposit, even in very small quantities in the tubing, making the printing worse in the future.”
Select presses are available with advancements for recirculation. For example, Roland printers have an internal clock that monitors ink usage. When a customer has not printed white for six hours, it activates ink circulation the next time a print with white ink is sent. Conversely, Roberts says if a customer is consistently using white ink, the system holds off on circulating. The clock and associated recirculation benefits the customer by keeping the machine ready for use.
Recirculation is one way to avoid clogging and settling, other methods are available to prevent white ink from clogging such as shaking the bottle, purging, and purchasing white ink in smaller pouches.
Shaking the ink bottle is a traditional and free solution to avoid ink settlement and printhead clogging. This method is typically best for print providers using white ink on occasion. To do so, Paul Leh, VP, Rainbow Pigment Co., Ltd., says print providers can regularly perform printer self cleaning, download the white ink when used, and shake it well before uploading again.
A more reliable method is to invest in a printer designed to purge a small amount of white ink on a regular basis to keep the inkjet nozzles from clogging. “This does add to the operating costs but is far better than the cost of wasting media due to spoiled prints where the white ink wasn’t confirmed to be jetting properly,” comments Paar.
Since white ink jobs may only represent a small portion of the overall print volume, select ink manufacturers offer white ink in smaller one-liter pouches so that the ink is more frequently replaced with well agitated, new pouches. According to Paar, using smaller pouches also decreases the chance of the ink expiring due to lower print volumes versus CMYK.
Not UV, but an interesting clogging preventative concept, HP Inc.’s Latex white ink offers macro and micro recirculation. Macro recirculation entails ink circulating through the printer from one bladder in the ink cartridge to another. The system reverses itself when one bladder is emptied. Micro recirculation occurs on the printhead itself as there are ink pumps on the printhead that keep the ink flowing and in a ready-to-print state, shares Thomas Giglio, business development manager, Graphics Solutions Business, HP.
Additionally, presses like the HP Latex R Series printers are available that permit the user to remove the white printheads when not in use and store them safely in the printer without fear of ink clogging. The printheads may then be reinserted when a white job is available.
Use White Efficiently
With liter prices, recirculating, and maintenance costs in mind, print providers need to ensure they are utilizing white ink properly and maintaining their equipment to cost efficiently take advantage of white ink.
Print providers can do so by ensuring they find the best applications and volume sizes that utilize white ink. White ink creates profitable work and any significant volume will more than make up for the higher production cost associated with white, recommends Larry D’Amico, sales director, North America, Durst Image Technology US LLC.
“The real concern is buying this option for your printer and then not using it,” he explains. Because these inks are susceptible to hardening and clogging, the most efficient way to use white ink is to put it to use.
Another important element for using white ink cost efficiently is to carefully maintain the ink and equipment. “Frequently agitated white ink jetted through clean, well-maintained printheads produces clean, crisp applications—clumped ink and clogged printheads do not,” states Manning. Clumped ink and clogged printheads create lower quality prints, which means wasting print and all involved consumables, not to mention having to print the entire job again.
Considering the cost of media and the higher cost of white ink, frequent misprints are a challenge many shops cannot afford. According to Manning, regular maintenance in accordance with manufacturers’ guidelines helps keep devices up and running as well as accurate, so the first print is most often the right print.
Designing & Printing
When designing and printing with white ink, certain applications and circumstances require opacity testing to achieve the proper output. The most common applications for white ink are as a base layer or spot effect on non-white substrates. Printing on clear substrates is also possible with the print either being a backlit consisting of a second surface color print or two layers of color and one layer of white.
The necessity of opacity testing depends on the customer’s needs, considering appearance, feel, and how it may change under different lighting conditions. For example, an application slated for a standard, consistent lighting environment mostly doesn’t require testing. However, Manning believes pieces intended for unique lighting scenarios or ones that shift should be tested with different opacities to determine the final result and how it appears in different lighting.
For example, day/night applications—also referred to as sandwich mode or three-layer mode—require significant testing in order to look the same under natural light during the day and artificial light at night. “These are created by laying down a color layer, then a white layer, then a color layer, so the top layer shows normally during the day and the color is reinforced under backlighting at night,” explains Manning.
When lit from the front, the white layer in between makes the colors appear in a normal post-white application. “Everything behind the white layer becomes irrelevant during these lightning conditions,” says Jason Hamilton, solutions architect, digital imaging segment, Agfa Graphics. “50 percent of the default white might be enough to offer this functionality, however depending on substrate and end user application this needs to be tested.”
Using similar processes, a printer can add spot color for different effects in varied lights—impressing audiences if executed correctly. According to Manning, added spot colors for different lighting effects should also undergo opacity testing.
Additionally, transparent and colored substrates require an opacity undercoat with white ink and should be tested. “Generally, we use higher resolution printing—more passes to print—for white ink to achieve denser output,” shares Juan Kim, CEO, Valloy Incorporation. He believes multi-layer printing provides more flexibility. For example, printing white in large dots with more passes than color in fewer passes.
Determining the amount of white ink and layers required on the substrate is essential to achieve the desired look and feel of a graphic. Both depend on the end use and the substrate type.
For black flexible substrates, it’s important to observe if the CMYK color tone is visible after printing on the white ink layer. “The ink layer should be able to mask the background of the substrate. The lowest amount of ink that yields the color is sufficient,” offers Nitin Goswamy, president, A.T. Inks. This may require one or more than four layers of white and CMYK to achieve the required white ink laydown.
For rigid, transparent substrates the same process applies. According to Goswamy, the goal is to apply the least number of white layers to get the right white background or opacity. As the ink layer increases, the chance of various modes of failure also increases. Thick layers can have adhesive failures or cause cracking. “It is advisable to use the least amount of white ink to achieve the desired result.”
A popular use for white ink is applying it to clear substrates, where first and second surface application occurs. Printing white ink on clear substrates is applied with several methods including setting an image file up with a white layer, using a print control utility, or RIP to select the white layer.
For first surface printing, a white opaque ink layer is applied to the clear substrate’s front surface. The most common white print modes used are an underflood or spot white ink, comments Giglio. The color ink is then printed on top of the white ink or the white ink by itself is printed directly to the substrate.
Goswamy adds, “in this case the surface of the printed article is exposed and may have lower life than back printed substrates.”
Second surface printing or back printing involves color-white and color-white-color modes with the same density whether the image is reflective or lit. The print is viewed from behind the clear substrate, with the print protected by the substrate. CMYK colors are printed followed by white ink on top of the CMYK ink. “The purpose of the white ink is to provide a white background and opacity,” shares Goswamy. In some cases, a four-color black is printed after the white layer to provide a solid background with maximum opacity.
For this process, Giglio says some presses offer a five-layer mode, which uses the combination of white and black to serve as a blockout so different images can be used on the front and back of the substrate.
Designing and printing an application with white ink involves opacity tests as well as questioning how much ink and number of layers are needed to ensure the graphic’s needs are met. PSPs should look at costs and determine a plan to ensure white ink applications offer an ideal return on investment. When executed correctly, a wide format digital print that uses white ink is a high-value application.
Dec2019, Digital Output