Discharge screen printing

Dis-charge printing is one of those things that some customers love while most printers will experience a cold shiver when the prospect of actually having to do some actually comes their way.

Screen printers and customers are often looking for strong vibrant colours on their dark coloured T shirts which plastisol deliver with such ease but at a cost. The print can feel heavy and rough as the heavy deposit required leaves its weighty impression.

The best way to describe the effect that discharge printing can give is just to describe the weight and softness that it offers when having to print light inks onto dark shirts.

Discharge inks managed to win for lightness and softness against plastisol inks for one simple reason. THERE IS LESS INK ACTUALLY GOING DOWN ONTO THE SHIRT.

This makes it lighter and softer to the touch compared to a heavy plastisol deposit that is often required on a dark shirt to achieve the required opacity on the ink.

So…how do we achieve a light print whilst ensuring a bright colour goes down… here’s the science…

The Discharge ink; system comes in two parts. There is a water and pigment mixture which is basically the ink and there is an activator which smells like rotten eggs and contains a bleaching agent.The two are mixed together at a certain ratio and then applied to the screen as normal to be printed as normal.

When the ink is printed is will immediately look poor next to a plastisol print. The plastisol ink will have a brightness and vibrancy which will be totally lacking in the discharge but all of the magic happens in the dryer.

The printed garment is placed on the dryer belt and run through so that the garment reaches about 170 degrees for approx 3 minutes.This is longer than plastisol ink requires to set but this extra time gives the bleaching agent the time to react with the heat and cause the underlying garment colour to be removed for the water based ink to sit on a light patch of bleached garment.

So rather than the ink trying to block out the garment colour to produce a brightness, the garment is effectively turned into a lighter colour just where the ink is to be deposited.This means less ink is required, hence the lighter softer feel with a print which feels like it is part of the fabric of the shirt.

There are a few compromises when going for dis-charge which may not always suit the client but generally they do offer a slightly improved ecological solution to plastisol and the feel is often preferred.

Discharge will only work for garments which are predominantly of a cotton composition and the fashion brands have been using discharge for some time but the garment selection and the design need to chosen carefully to work with discharge inks.

In conclusion…they can be trickier to use for the screen printer, they stink out the workshop with that rotten egg smell but they can deliver a superior feel if softness is important.

If you take a look at the pictures below you will see how the two different inks perform next to each other.

Picture 1 on the left shows a slightly brighter look for the plastisol ink compared to the discharge, but picture 2 on the right shows the cost of that brightness. The heavy plastisol deposit on the right of picture 2 is in direct contrast with the discharge ink where you can still see the warp and the weft of the cotton fabric through the ink.This gives it that ‘part of the shirt’ feel which plastisol finds hard to achieve.

The Shirtworks sales team know all of this and can advise you accordingly. Beware of those printers who cannot talk the talk and walk the walk like Shirtworks.

Why not test those other printers out by asking them some questions.

Stay tuned for the next blog……

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