Learn how to create bright and beautiful discharge effects in this step-by-step guide from Paul Woodward of MagnaColours

Discharge inks work by removing the dyed areas of reactive dyed dark garments to create a different colour in its place.

“The pigments used in discharge inks are impervious to the discharge process so, essentially, they replace the colour that was there previously on the garment,” explains Paul Woodward, technical support representative of the water-based screen printing ink specialist, MagnaColours.

“Some refer to it as a ‘bleaching’ process, however discharge inks don’t damage the cotton fibres. The end result is an extremely soft print that can have little to no handle on the garment, whilst offering extremely bright colours.”

In this step-by-step, MagnaColours used its latest discharge formulation, MagnaPrint Discharge LO. LO stands for low odour because this ink system was developed not to have the unpleasant aroma when printing that discharge inks are often associated with.

“Instead, Discharge LO offers a mildly sweet aroma that’s far more preferable for the shop floor!” says Paul.

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STEP-BY-STEP: DISCHARGE PRINTING

(1) Discharge ink is extremely versatile when it comes to the type of artwork you can screen print, ranging from solid, vector-style designs to photographic halftones and detailed designs. We chose a playful motif with plenty of colour to show off the bright effects you can achieve with discharge inks. We recommend using 43-62T (110-158) mesh screens for solid areas and 77-90T (196-230) mesh for halftones when printing with discharge inks. As this design was made up of completely solid print areas, we used 62T (158) screens for all colours.

(2) Once we had selected the five different colour references for our design (plus Super White for the white areas), we were able to mix the colours using MagnaPrint Eco-Pigments and the Discharge LO ink system. We generated the recipes using the MagnaMix software and selected our required quantities, then used an automatic MagnaTint pigment dispenser to add the colours to our ink pots. The ink then needs to be thoroughly mixed. If you don’t have a dispenser, you can weigh out each pigment – MagnaMix provides accurate recipes for thousands of different colours.

(3) For this guide we used four different colour shirts – 100% cotton black, 100% cotton navy, 90% cotton/10% polyester heather blue, and 50% cotton/50% polyester grey – to provide a nice range of results and effects.

(4) When setting up the screens on your press, make sure that there is around 3-5mm of off-contact distance between the mesh and the garment. We used a medium 60-90-60 shore rectangular squeegee and set the blade angle to 15° (10-15° is ideal). Screen order in the machine should go from smallest to largest print areas and white should always be last. This is to avoid pick-up during the screen printing process: as white is the brightest colour it would stand out more on successive prints if white discharge ink was accidentally picked up from the garment onto a later screen. Putting it last avoids this.

(5) Discharge LO, like other discharge inks, is a ‘two-pack’ system and uses 6% activator (Activator AB) which is mixed with the base ink before printing. Following activation, the ink should be left for 10-30 minutes to dissolve and has an active life of up to eight hours (depending on environmental conditions). To avoid wastage, only activate the amount of ink needed for your run (usually 1-2 kg per screen). Always keep activated ink next to the print station in a sealed container.

(6) We used an eight-station M&R Sportsman EX automatic screen printing press to print this design.

(7) When printing with discharge systems, inks initially printed onto the fabric will appear muted or dull until they have been cured. Curing discharge prints activates the ‘bleaching’ process.

(8) It’s now time to send the garments down your dryer. We used an M&R MiniSprint 2000 dryer at 170°C for 2 1/2 minutes. Depending on the size of your dryer you may need to adjust your process, but we recommend aiming for 2 1/2 to 3 minutes at that temperature overall.

(9) Once cured, the colours really start to sing and show how the heat has activated the discharge process and replaced the colour in the shirt. The different shirts show some variables in the effects you can achieve. The black and navy 100% cotton shirts provided really bright and solid colours.

(10) The lighter colours and polyester content in the other shirts created a more muted and vintage-look discharge effect.

For more tips on printing with discharge inks, check out our April 2022 issue here