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How To Choose The Right Screen Printing Ink For Your Business

How To Choose The Right Screen Printing Ink For Your Business
27/02/2019

Choosing the right screen printing ink for your business involves some research and the aim of this article is to help you contemplate the most important considerations and how the qualities of each ink type fits with your business model. As a company, Dalesway Print Technology represents the Lancer brand of screen printing ink. Lancer manufacture all these types of ink, so we have no bias towards one type of ink beyond what the facts state.

What is in ink? Fundamentally the main ingredients of ink are –

Pigment to colour the ink A carier or base (the main component in a liquid form that “carries” the other contents) Binder that glues the ink to the substrate Main types of screen printing ink Plastisol based screen printing inks

The mainstay of screen printing has for many years been plastisol inks. These versatile inks are superbly easy to use and the majority of garments both in retail and the promotional industry will be printed using plastisol inks. Plastisol ink only cures when it is heated to the correct temperature and the resin carrier absorbs the plasticiser to form a continuous sealed film of plastic. This is why plastisol ink is so easy to work with and never dries in the screen.

Water based screen inks

Water based screen inks offer some definite advantages and remains a very popular choice, but in many instances, for the wrong reasons and we will explore these throughout the article. The binder in water based ink nowadays is either acrylic, polyurethane or a blend of the two. In the past it tended to be either latex or acrylic. Curing of water based ink takes place in two stages: First all the water (carrier) has to evaporate before the binder can permanently adhere to the substrate.

Hybrid screen print inks

Finally the new breed of hybrid inks will be considered. These inks offer some of the benefits of both plastisol (ease of use) and water based inks (lack of phthalates and PVC) while eliminating common problems associated with each as well. On the face of it, it seems to be the most logical choice, but of course, with new technology comes higher manufacturing cost both from a technological point of view and economies of scale in production. Curing and drying requirements for different inks As a screen printing shop, the purchase of a screen printing dryer is a big and important decision. Your choice of dryer will be determined by the ink or inks you plan to use. Curing happens when the binder melts or the base cures thermo chemically to form and bond between the base and the pigment.

Plastisol

Plastisol inks are the simplest and fastest to cure, thereby keeping energy use to a minimum and requiring the smallest dryers. You can for instance cure up to 110 A4 sized prints on a dryer like the one pictured – the Vastex D100. This compact dryer fits easily on a table the size of a desk. This is not only useful for smaller businesses that are short on space, but for the increasing number of event printers that take equipment to a variety of shows and festivals. The Lancer 500 series phthalate-free plastisol inks for instance only need to cure at 165°C for 15 seconds. The process typically takes 45 seconds.

Hybrid inks

Hybrid inks require longer drying times and therefore a slightly larger dryer. Moving up the range with your dryer does actually give added versatility if you print using plastisol inks as well, since you will be able to cure more items per hour. The Lancer range of Evolution, PVC and phthalate free inks for instance require a cure time of 45 – 60 seconds at 160°C. You could therefore use a dryer like the Vastex LittleRed X2, which is still very compact.

Water based inks

Water based inks require the longest cure times and therefore much larger dryers, which leads to much higher energy consumption as well. Herein lies the first of the points where water based inks are simply not as “green” as most printers think. Before the actual cure starts, all the moisture deposited onto the garment from the water based ink must be removed by evaporation. Remember half of what is in your pot of water based ink is simply water. This process takes time and the evaporation process itself has a cooling effect thereby requiring more heat and time, hence the need for a much larger dryer. Dryers equipped with forced air tend to be the best choice for curing these inks and this also increases energy consumption.

Lancer Aquatex water based ink requires around 90 seconds at 177°C for a full cure. When curing poly cotton blends for instance, the cure time would be longer at a lower temperature. If you need to add a retarder to slow down the ink drying in the screen, this will further add to the curing time. Cure time can vary greatly between brands of ink as well, with one other example of a popular ink requiring 2 – 3 minutes at 160°C.

Shelf life, pot life, and dwell time considerations Shelf life: How long the product lasts on the shelf in storage in the original sealed container.

Pot life: How long is the ink useable if it has been mixed or activated.

Dwell time: How long can the ink be in the screen mesh, in action printing and then at rest with no action before it starts to dry and clog the screen mesh.

Plastisol

Plastisol inks typically have a shelf life of over fifteen years in a sealed container. Pot life standard without special additives like a catalyst for nylon is typically seven to thirty days (leaving the lid unsealed will have the liquid components open to evaporation). Dwell time for plastisol in the screens is three to seven days without excessive notable change in the ink and print capability (will not dry in the screen mesh).

Hybrid inks

Hybrid inks typically have a shelf life of over seven years in a sealed container. Pot life standard without special additives that are time sensitive is typically three to fifteen days (leaving the lid unsealed will have the liquid components open to evaporation). Dwell time for Hybrids in the screens is three to five days without excessive notable change in the ink and print capability (will not dry in the screen mesh).

Water based inks

Water based inks typically have a shelf life of one to two years in a sealed container. Pot life standard without time sensitive additives is typically eight hours to two days (leaving the lid unsealed will have the liquid components open to evaporation). Dwell time for water based inks in the screens is typically minutes before the ink will start to dry and clog the screen mesh, evaporation retarding chemicals can be added and wetting sprays used in the printing process.

Hand feel and artwork considerations The hand or feel of the printed garment can play an important role in the choice of ink system. It is much less of a factor in the promotional and retail printing markets where plastisol is often still the go to choice.

This particular attribute is in many cases what leads printers to select water based over other screen printing inks. The advent of hybrid screen print inks like Lancers’ Evolution range do however give printers more options as the hand feel of Evolution PVC free ink is much more similar to water based than plastisol ink.

Plastisol overall will feel the heaviest as it sits on the fibres and into the weave without the penetration from a thinner viscosity inks. Therefore the ink “sits” on the garment. Keep in mind that this depends to a very large extent on the artwork and the mesh choice. A large block print such as often seen on athletic garments will always feel heavy when printed with plastisol. Such garments are normally not suited to being printed with water based inks for the simple reason that water and synthetics don’t tend to like adhering to each other.

When large blocky artwork is not demanded, a skilled artist can create a design that uses plastisol and yet does not feel heavy. Print trials conducted in our own facility and during trade shows have also proven that plastisol prints on high thread count mesh and designs that are four colour process printed using plastisol and very high mesh counts are so soft, most people would never know it was the exact same ink as can be found on some rather less appealing and poorly thought out prints.

While a water based ink will always be required for softness and absorbance as in something like a tea towel, other applications can certainly benefit from either plastisol or hybrid screen inks alongside well thought out artwork.

Cost per print comparison As screen printing inks go, you can be sure that plastisol is the most economical on a per print basis. Every ounce of product in your pot is actual solids that stay on the garment. What you pay for is literally what you get.

Evolution ink from Lancer is a hybrid that also offers you 100% solids as in the case with plastisol. The only reason it is less economical is because the technology and safety certifications behind this system does not come at a low cost.

Water based ink offers the least cost effective option. Each pot consists of around 50% solids with the rest being water, preservative, surfactant and so on. Not only is the actual product cost considerably higher than it might seem from the sticker price, but the additional demands of curing water based ink adds further to the overall expense as discussed previously.

Plastisol vs Waterbased Ink Yield “Green” Credentials For many, this topic will be slightly emotive as each product has its proponents. All this aside, facts are facts and as a print shop owner, you need to dispose with emotion and marketing misdirection and review facts.

Plastisol

All plastisol inks contain PVC. PVC is not quite the enemy of mankind to the extent that it is made out, but it is a consideration especially for next to the skin decorations and children’s garments. The vast majority of good quality plastisol inks will no longer contain phthalates, but do check that your chosen plastisol complies with REACH and EU Directive EN71 that prevents commonly used components such as formaldehyde, heavy metals, azo dyes, lead, arsenic and other harmful substances from being used. Provided your chosen plastisol complies with all current safety certifications, you are fine.

Solvents are most often used for clean-up which is perhaps the biggest bugbear for the anti-plastisol brigade. Citrus based ink washes that are biodegradable is also available and these are both a safe and effective alternative to traditional solvents used for clean-up. Either way, when proper clean-up procedures are observed, the use of solvents is very low indeed and any product going down the drain absolutely minimal. Such procedures are essential irrespective of inks used. Learning proper clean-up procedures not only ensures your most cost effective inks are as “green” as possible, but ensures that profits are not washed down the drain along with unnecessary chemicals which is kinder on the environment too.

Hybrid inks

Regardless of current legislation and lab safety reports relating to plastisol inks, some sportswear companies have chosen to go PVC and Phthalate free. These companies include big brands like Nike, H & M, Adidas, Puma and S. Oliver. Evolution hybrid screen ink is a replacement for plastisol that has no sulphur emissions and contains no restricted chemicals. In addition, no airborne VOCs are emitted and there is no wastage as the product consists of 100% solids just like plastisol. Not only is there no wastage due to the loss of water, but curing also requires less energy than water based inks that demand evaporation and curing/fusing, albeit more than what plastisol requires. This hybrid PVC free plastisol style ink meets all compliance standards and is safe for children’s’ wear and meets “next to skin” regulations as well.

Water based inks

These inks are usually cleaned up with water which adds to the appeal especially in educational institutions. However, this should never mean that whatever is left on a screen gets washed down the drain. Proper clean-up procedures are just as essential as with plastisol inks, but this fact is often overlooked.

Water on its own will never properly coat the fabric being printed, so water based ink needs to have a surfactant added to make it “wetter” and printable. Without surfactant water based ink would bead up and make a very uneven print. The problem with surfactant is that some of these products can be very harmful to marine life. APEO is one such commonly used surfactant. Another drawback of water based ink is the need for preservatives such as formaldehyde to prevent moulding of the ink. Water based inks also emits VOC’s.

Solvent retarders are often used to keep screens open longer and these are of course toxic. Once a screen becomes blocked, very powerful solvents are needed to reclaim the screen and in many instances, locked screens may be impossible to reclaim.

The extended evaporation and curing/fusing requirements of water based inks also make them the least energy efficient solution.

Pros and cons of each ink system Plastisol (Example: Lancer 500 Series)

Pros Lowest cost per print Lowest amount of energy required to cure Requires the smallest dryers Never dries in the screen No production stoppages to clean blocked screens Faster production speeds No wastage from evaporation, 100% solids No airborne VOCs Can be printed through a variety of meshes (43 – 120T / 110 – 305) Wide range of special effects available Long storage life of decades Pot life measured in weeks Dwell time measured in days High opacity thanks to 100% solids

Cons Contains PVC Heaviest hand feel (mostly a problem on large solid areas of print)

Hybrid (Example: Lancer Evolution Ink)

Pros PVC free Contains no harmful or restricted chemicals Soft handle Never dries in the screen No production stoppages to clean blocked screens Faster production speeds No wastage from evaporation, 100% solids No airborne VOCs Can be printed through a variety of meshes (43 – 120T / 110 – 305) Some special effects available Meets Oeko-Tex 100 safety standards Meets Nike RSL safety standards GOTS certified Registered at the ZDHC Long storage life Pot life measured in days Dwell time measured in days High opacity thanks to 100% solids

Cons Higher cost than plastisol but less than water based

Water Based (Example: Lancer Aquatex)

Pros Very soft hand feel of final print PVC free

Cons Highest cost per print High level of waste – only 50% solids Highest energy usage for curing Requires very substantial dryer size Screens can easily become blocked causing production stoppages Blocked screens may be lost if strong solvents cannot undo the blockage Solvent retarder may be required to slow down drying in screens Emits VOCs Colour shift during curing – as water evaporates, colour becomes stronger More compatible with coarse mesh (33 – 65T / 83 – 163) Screens must be cleaned down for all breaks and shift changes to avoid blockage Contains surfactants that are harmful to the environment Contains preservatives such as formaldehyde to prevent mould Low opacity due to only 50% solids although some brands have addressed this issue Shortest storage life Pot life measured in hours Dwell time measured in minutes

For more information follow this link: How To Choose The Right Screen Printing Ink For Your Business

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