Screen printers will mostly agree that they do not like using water based inks.
In a fast paced print environment where 'time is definitely money' there are significant problems with using water based inks instead of plastisol inks, which are oil based.
The clue is in the name.
A water molecule is approximately 50 times smaller than an oil molecule and is lighter in mass and able to move more quickly.
This size and speed difference means that evaporation occurs much more readily with water based inks and this is the primary issue for screen-printers.
Setting up a 5 colour job on an automatic press can take anything from 25 minutes to an hour depending on how many printers are working on the task, the complexity of the order and what inks are being used.
Once the screens are set up and registered, the printer fixes the squeegees and floodbars into position and then turns to the inks.
This is where life can turn into a drama.
If plastisols are being used then the printer can casually saunter about his or her business, pouring them into the screen, washing their hands after, having a quick pee and then put the kettle on for a nice cup of tea before turning their attention to making final adjustments, running a test print and then starting the print run.
If water based inks are being used then the stress receptor in the screen-printers brain gets a dose of cortisol, initiating a fight or flight response and serious concern that everything is about to unravel.
Evaporation is the enemy and the thief of time.
Those water based inks, as soon as they are poured into the screen begin to hatch their plan to make your life uncomfortable. As evaporation occurs, the ink begins to dry out. The pace of this drying out is variable depending on temperature and humidity but the effect means a race against time is initiated to stop your screens clogging up.
If you are lucky/skilful and your screen registration has been good to begin with then getting into the print run should have been fairly quick. Your cortisol levels even out and slowly subside to be replaced with a feeling of relief.
If you are unlucky/ ill prepared then a multitude of everyday problems that are common place on a print carousel can mean you spend unwanted and unplanned time crouched under your carousel with a wet rag vigorously scrubbing out dried ink from the warp and weft of your screen.
All of this scrubbing mans that no printing is occurring which means that all important deadline for the courier to take your goods to the customer is looming which means another squirt of cortisol!
Evaporation is stealing your time!!
What can you do?
Preparation is the key.
Always ensure that you are going onto a custom t-shirt which you have proven to yourself works for water-based ink. Light coloured shirts are generally never an issue but if you are discharging into dark garments, this is critical. They have to be 100% cotton and you need to be sure they work before setting up the press. Discharge results can vary hugely between the brands. A navy blue t-shirt from brand X and a navy blue t shirt from brand Y, printed with the same inks at the same time can produce very different results. Never promise an exact Pantone colour match for discharge jobs unless you have undertaken a lengthy trial and testing phase with that garment and have spent hours fine tuning the pigment mix for your ink.
Always ensure that the prepress work with screen making and screen taping has been done perfectly. Those screens should come out of the screen room with all pinholes taken care of, zero chance that the ink can creep under the frame/edge taping and a perfectly washed out stencil.
Always Make sure you have chosen wisely with your mesh counts. Go for the coarsest mesh possible while not overdoing it. A 43t mesh will always be 'wetter' in the cleft of the warp and weft because it holds more ink. More ink means a slower rate of evaporation. Finer mesh counts in the 77, 90,120 and 140 categories will increase your rate of drying in direct correlation to the increase in mesh count.
Always use the tightest tensions possible on your screens. A loose screen, which works perfectly ok on the manual press for a single colour plastisol job, has hidden dangers for a water based job. The aperture between warp and weft has relaxed and closed a little becoming lazy and grabby. Where possible, make sure your screens are between 20 and 30 Newtons.
Always use hard, sharp squeegees. This will ensure that the ink is completely sheared through the screen.
Always 'up the pressure' a little on your squeegee. The aim is to push the ink into the fibre rather than laying on top which is what you would typically be doing with a plastisol. Remember that your customer has probably chosen water based inks for 2 reasons. They are kinder to the environment and they feel softer. This softness is partly achieved by pushing into the fibre. This is true for discharge onto dark garments as well as standard water-based onto light coloured garments.
Always run a water based job with a little help. A sidekick can be in the places where you are not, doing the things that you can't do because you are busy doing something else to avert a disaster.
Always make sure you have dumped way more than enough ink in the screen to help keep it wet and to avoid it partially running out during the print process. This is where your sidekick can help as they dash around the carousel to make sure there are no potential problems with ink about to run out while you are printing. Keep the flood-bar a healthy 3 mm above the surface of the mesh so that it pulls a 'weight' of ink back during the flooding process. This 'weight' helps to keep the screen wet.
Always use a retarder. I have had mixed results with different ink brands and their retarders. Sometimes I feel they do little to help so…..
Always keep a small garden/greenhouse water spray canister near your carousel to douse the ink with a little water mist while in the print run. Your sidekick is invaluable here.
Always ensure that any interruptions that you might normally experience during the natural course of the day are not going to crop up while you are printing the job. You do not want to be pulled from the carousel to sort out a mini-drama that seems to be calling your name. The water in that ink won't stop evaporating just because you are not there. This also means your team. Make sure the folders and packers have had a wee before setting off on a 2 hr print run and don't set up your job just before lunchtime without telling everyone involved that lunchtime is cancelled today!!
If you have done your preparation and your karma is perfectly aligned, you can get some excellent results with water-based inks.
They have a 'matt' quality and a softness that plastisols can never achieve.
They have that 'part of the garment' feel that plastisols can not quite achieve.
They have the moral high ground that plastisols can never achieve.
If you are new to water-based screen printing then brace yourself for that rush of cortisol, learn to love it, accept that will not work for everything and try not to overpromise its virtues to your customer.Proceed cautiously, with preparation and with quiet haste and you will win some victories