Polyester is popular again.
Not in a post ironic disco fitted groove strutting kind of way, but popular with those that like to cook up a sweat; stretching, lunging, busting a gut, honing those pecs and glutes.
All manner of ‘teamwear’ type styles are now available for your football , hockey, basketball, cross country and quidditch team.
Your first decision may be what colour configuration you require with your teamwear but the second is going to be how your logo or design is placed onto your garment and what process is best.
This is not so straightforward and some consideration is required. The choice you make will be dictated by your design/logo in conjunction with your garment choice. The number of colours, the detail in the logo, the size of the logo, the colour and weight of your garments will all shape this decision.
Your Shirtworks account manager will be your sounding board but below is an overview of these considerations and the reasons that they require some expertise and thought.
1 Why is polyester a trickier proposition to decorate than a traditional cotton T shirt?
The main issue with polyester is the type of dye required to alter the colour of the garment. ‘Disperse’ dyes are typically used in conjunction with a vat dying process.Tthe chemical makeup produces a smaller dye molecule which helps binding and absorption with the smooth plastic fibre of a polyester garment. The problem with these types of dyes is the reaction that is generated at a molecular level when they are ‘cured’ during the print process. The reaction causes ‘dye migration’
2 What is dye migration?
Traditional screenprinting requires that a ‘plastisol’ based ink is used to get the image onto polyester garments. Plastisols are great for cotton, producing a bright and robust print finish but the brightness and colour can suffer when printed onto Polyester. This is down to the dye and the reaction that occurs when the garment reaches the 165 degree celsius required to cure the ink on the garment.
All garments need to be heat cured if they are being printed with plastisols. Printers use heat tunnel dryers with conveyor belts that draw the garment through the tunnel to allow it to be exposed to the heat for a controlled period of time. At the required temperature for ink curing, the dye produces a gas containing the tiny molecules of dye particle. This permeates through the slightly porous ink that has been printed on top of the garment. This permeation pulls the dye molecules through the ink causing a colour change in the ink.
The effect is often delayed and can take up to 24 hrs to complete which is particularly frustrating for printers and customers. This delay can mean that garments leave the workshop looking fine but suffer during transit and end up looking ‘affected’ when they reach the customer. Printers all over the world struggle with this problem and a small number of solutions are used to reduce the migration effect but none are 100% guaranteed.
The method we like to use at Shirtworks is to run the garments through the dryer first to allow the majority of the ‘gas reaction’ to occur before printing. This ‘cooks off’ most of the gas but not all. We then print a grey underbase which has a lower cure temperature to block and seal the fibres before printing our plastisol on top. The lower curing temperature means the gas permeation effect is further reduced at the point of curing because the base has cured more quickly.
In most instances, this eradicates the problem or reduces it to a point that is acceptable. The downside is that you have a heavy print due to the heavy ink deposit. This ‘heavy’ feeling is exacerbated by the weight of the garment, or lack of it. Polyester sports tops are usually at the thinner end of the garment weight spectrum.
Thinner garments are more comfortable to wear if you are engaged in a sporting activity; they dry out more quickly and feel less cumbersome. If a heavy plastisol print is used, this can feel disproportionally heavy compared to the weight of the garment.
3 Why does the weight of the garment affect my decision?
If your garment is a thinner weight at around 130 -140 gsm, it would be sensible to choose a decorative method that is thinner or lighter.
The two options which offer such a proposition are DIGITAL TRANSFER and VINYL applications. Transfers are printed from a laser or inkjet printer using special inks, they are then cut to shape on a cutting plotter and then placed on the garment and heat pressed onto the garment for a specific time and pressure.
Vinyl is micro thin plastic which is in a roll format. It is loaded into a cutter and the design ( usually text for vinyl) is created in Adobe Illustrator ( or similar vector program) and then transferred to the memory of the cutter where a small blade is directed to move quickly across the surface of the vinyl to ‘score’ a cut line in the shape of the desired artwork.
A weeding process is then required to remove the parts of the vinyl not required for printing. What is left is the artwork which is then heat pressed onto the garment at the required heat and pressure. It is standard practice to use this method for individual names and numbers that ae typical on the back of sports garments.
4 Why does the amount of detail in my design affect my decision?
Professional sports teams can often have very intricate logos. These logos have often evolved from old heraldic designs and were never intended for printing onto garments. Most have been modified over the years but if there is complex detail then digital transfers offer the best solution. They can produce images at a much higher resolutions, of 300 – 600 dpi typically, than screen printed logos and if the logo has a definitive edge or border, the cutter plotter can produce a crisp and clean result from a digitally printed transfer.
If your logo has a gradient, this would also be a reason to use a digital transfer. ‘Gradient’ is the terminology used to describe how a colour changes completely or fades/darkens across your image subtly. In order to achieve this effect in any type of printing, the image is rendered into dots of various sizes with varying spatial relationships.
A digital printer can print extremely high resolutions to a point where it is extremely hard for the human eye to discern these dots or spatial relationships. This produces a ‘fade’ or ‘blend’ effect in the eye of the observer creating the gradient. Screenprinting can only produce these gradients coarsely by comparison at approximately 65dpi. At a distance, the human eye cannot see the dots and so perceives a smooth transitional gradient.
The distance required from image to human eye is greater for screenprinting than for digital printing. It would not be unusual for the observer to be holding the logo as close as is comfortable from their eye and still not be able to identify the actual dots printed that created the gradient.
5 What about embroidery?
Embroidery is possible on heavier weights of polyester but Shirtworks recommends a garment weight of 175 gsm or over. There are caveats. Dense, stitch heavy or large designs are not advisable on 140 – 200 gsm garments.
A ‘dense’ or ‘stitch-heavy’ design is described as a piece of artwork or logo which has background colours and is ‘blocky’ in its overall appearance. Breast or left chest embroidery is the common position for embroidery and 9 cm wide by 9cm high is a sensible maximum dimension. A logo that fills that entire are is going to be heavy and around 20,000 stitches.
A logo that fills that area but does not have solid background could be half that stitch count and weight and would be the more sensible option. Small logos tend to be anything from 3000 stitches at the very least to around 15000 stitches for a larger ‘crest’ or ‘shield’ type design. The latter is going to be too heavy on anything under 200 gsm garments.
6 What is sublimation printing?
Sublimation printing is a technique that can be used on a number of different surfaces and materials. When we talk about sublimation printing with particular reference to polyester garments the concept involves the migration of colour from digitally printed transfer paper into the fibres of polyester at a micro molecular level.
’Sublimation’ means the transition of a compound from a solid state to a gas state without it passing through a liquid state.The ink is in a solid state while on the transfer paper and when the paper is pressed against a polyester garment and then subjected to a specific heat, time and pressure application via heat press, the solid ink becomes gaseous and migrates into the fibres of the polyester where is becomes a solid once again when it is cooled.
This differs to screenprinting where the ink is layered or squeegeed on top of the fibres and is bonded by virtue of the fact that the inks original liquid state before curing could partially grip the fibres of the garment along with the inks adhesion chemistry.
‘All over’ sublimation printing is now commonplace for small orders. This is where the garment has an entire 100% covering of logo/design detail. Pricing is expensive at approx £25 per garment but the possibility of getting your team kitted out in a completely bespoke design is attractive enough to make this viable.
The process involves cutting the fabric panels of the garment and heat pressing a large format transfer paper onto the panel to sublimate the image into the fabric. The garment panels are then sewn together to create the finished garment.
There is more to cover but that is the basics.
Who thought T-shirt printing could be so complicated?
Author Arron Harnden www.shirtworks.co.uk