Discharging in screen printing

Screen printing is the stalwart process of the garment printing industry. Tommy Newton has spent over 20 years working on the screen print process at Screenworks. In this article he shares his thoughts on discharge printing and its place in the screen printing armoury.

Discharging uses the same process as traditional screen printing, but instead of printing a design on top of the fabric, discharge inks remove the original dye in the garment fabric where the design has been marked.

Discharge inks can either be used to just remove the original colour from the garment or pigments can be added to redye the fabric to match the client’s design. This effect is created by adding a discharge agent to the ink that removes the dyes in the fabric and replaces them with the desired ink colour. With the discharging technique, rather than the heavy handle of having ink laying on the surface, the design is printed directly into the fabric using water-based inks which redye the fabric giving it a softer feel and look.

Although it sounds similar to bleaching it’s a gentler process on the fabric and does not damage the fibres in the T shirt or product.

What are the pros and cons?

This process gives a comfortable and soft-feel design that blends seamlessly with the product printed. It delivers an incredibly durable print and is a cost-effective way to create a unique and engaging design.

However, there are some limitations to this printing method.

This process only works effectively on cotton garments. Cotton blends and man-made fibres won’t work as well. Absorption of the discharge dye is higher and previous dye removes far better from cotton fibres, meaning the design will be more vivid and any new pigment will take well.

Due to the nature of the process and the inability to predict exactly how the ink will remove pigment from the fabric, with discharge printing it is more difficult to Pantone match. For clients looking for this service it is not a suitable option as it can be tricky to guarantee exact colour matching.

Discharge printing is most effective on dark garments and should only be used on coloured fabrics. Light coloured or white fabrics can be printed using standard water-based inks as no discharging is required.

The process does take more time planning. After screens are developed you must apply a stencil hardener to help prevent the breakdown of emulsion in production, and also allow time to clean down all screens and squeegees as these tools can’t be left overnight before cleaning.

When to use this technique

One great use for this technique if clients want a particularly vivid or multicoloured print on a dark fabric is to combine the discharge process with a print of conventional plastisol ink on top. By using the discharge ink as an underbase and removing pigment from below, a vibrant soft handle print is achieved.

Whether or not to employ the technique of discharge printing is really a choice of what style or impression the client wishes to give. Is the client looking for bold and bright, or muted and stylish? Do they want a design with vintage feel type, or a striking multicoloured slogan?

Safety

Using discharge inks does come with some safety concerns due to their chemical components.

All staff need to be properly trained and equipped with the right safety equipment.

Due to fumes from the inks they must be used in a well-ventilated area and respiration equipment worn when required.

No contact can be made with skin and the correct specialist chemicals should be used in the process.

Any waste should be collected by an industrial waste collection company.

Growing trend?

Discharging has been around for quite a while, but has gone through cycles of popularity. We are now really seeing a growing interest in discharge inks.

This may be due to a trend for comfort in garments, but also looking at the popularity of eco-conscious styles, which use natural materials and have a more muted aesthetic.

Tips

  • Test colour swatches provided by garment brands to see how each fabric reacts with the discharge ink. This way you’ll be able to tell how effective the ink will be at removing all pigmentation from a certain colour fabric or brand T shirt.
  • Once the discharge ink has been mixed you have usually a few hours working time. The ink cannot be left overnight as it air dries where traditional plastisol ink will not. Make sure you have scheduled around this working time and planned for late shifts with printing teams if necessary.
  • Just like any other screen print process it is crucial screens are properly cleaned and reclaimed.
  • Make sure all involved in the process are using proper safety equipment, and staff are properly trained in dealing with the inks involved, including their disposal.
  • Advise clients that the garment(s) should be washed before wearing to give the full effect of the soft design.

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