Grafica News - april 2012


Summary of presentation made by Michel Caza in PRAGUE on 21 March 2012

Garment Textile Printing : The State of the Art

Place and importance in screen & digital printing technology

  • I have been fully involved, since a few years, in a lot of audits in textile manufacturing and printing companies in Tunisia, Morocco, India, Thailand, China, France and Turkey… 50 companies audited from the quality, technical, environmental and social angles.
  • Both integrated department in factories and independent screen-printers.
  • I was as well in “relatively” small companies as in HUGE companies of which the size seems purely unbelievable in Europe and even in USA !
  • The biggest, Shenzhou in Ningbo – China – 28,000 employees, 200,000 m2, a staff of 1,600 peoples on 20,000m2 for the screen printing department only !!. 26 automatic carrousels, 4 kilometres of “long tables” ! They print 350,000 pieces per day ! Can you believe it!
  • Mills in Tirupur – India – from organic cotton fibre to finished garment….
  • Some of them start from fibres, others from spinning, others from weaving, others from weaved textile and cut, screen print, put transfers and embroidery, sew and mount… Some simply print but no one – except in sublimation transfer – use digital printing !!

Both family work and huge industrial application

  • YES, both. We will see that under another angle when I shall conclude !
  • Of course, I visited those giant companies, but also a lot of smaller companies having between 25 and 100 employees, either independent and/or small department in huge plants.
  • One thing is clear : garment printing is almost totally screen printed – once again, screen printing is not an industry, but a technology used by many industries and this is valuable for digital printing – textile printing is 30% to 35% of the applications of screen printing.
    This is more than the 20-25% - the graphic and sign part of applications,- but less than the 40 or 45% of industrial applications (electronic, glass and ceramic, packaging, automotive, toys, etc.).
  • Digital seems to take over screen ? That is why most Fairs – this include FESPA’s fairs, but we try to change it – does not reflect what is the real place of the screen printing technology. As too much based on “Visual Communication”, due to the place digital printing took in these “imaging technologies”, the visitors (and the magazines) receives the (false because partial) feeling that digital printing took definitely over screen… But what about all the other applications ?

The actual technology

  • The actual technology remains for me a “paradox” : a mix of primitive and hi-tech tools and habits !
  • You have companies with a lot of sophisticated carrousels, even with CTS, image setter, etc. and on the other hand manual printing with un-sharp squeegees and un-tensioned screens…
  • From the giant plant to the garage (you know the one the Americans were so keen of : “make one million dollars in your garage “!)
  • A mix also of big investments and simple manual long tables, of both some very cleaver and skilful peoples and others who learned “from the old timers” a lot of bad and even strange habits.
  • But, everywhere, I met a desperate need of schools, of training, a huge difficulty to find skilled peoples…. Such a school as DMI in India is the “exceptional exception”, both for graphic, textile and industrial applications of screen printing.

And, at my surprise, I found that the technical mistakes and failures were the same in all the countries !

Quality and Equipment

  • I put those two elements together… deliberately !
  • You have often the equipment without the skill… Sometimes the skill without the equipments : here, you have the key. No one ALONE is sufficient to reach the quality required and expected by the final customer and end-user.
  • I found millions of Euros in investments and… the absolute minimum, the cheapest manual tools, the “ultra-clean”… and the “ultra-dirty”.
  • The customer want perfect – and green – products… Produced in a green manner, I will say that again ! ! I saw the best equipments and products used in a bad manner… I saw poor equipments combined with good products and also … both bad !
  • There are two causes of the too often insufficient quality of the printed products:
  • Causes related to screen printing
  • Causes related to other factors anterior to direct screen printing or transfers

Screen printing problems

  • Lack of sharpness, of definition, of constancy and repetition, lack of adhesion and elasticity or resistance to washing… both for direct screen printing and indirect one – I mean transfers.
  • The causes are multiple, from prepress, (even sometimes from the customer’s studio artwork), from the colour of the fabric on the screen, its stretching often totally too low and irregular, lack of good contact when stencilling, damaged lamp, the squeegee blade un-sharp and damaged, the printing strokes repeated several time and sometime in both directions, badly prepared or mixed inks, wrong pigments, strange drying practices, the policy of “immediate profit” ignoring the medium or long term, etc.
  • Sometimes one or a few of those mistakes, sometimes the all of them… cumulated !

Other Problems (softness, washing resistance, extension, problems due to the dyes and additives, hard water)

  • I could also realize – and correct – many other problems that could be sometimes attributed WRONGLY to the screen printers such as the ones mentioned above : lack of adhesion or/and suppleness, migration in a clear screen printed colour (white for example), lack of softness of the fabric, etc.
  • I found several problems related to the use of “cheap” pigments in the dyes – especially colours containing magenta and yellow pigment. It is clear that those pigments, to be resistant to the solar light and other chemical and mechanical constraints, then to migration before or after washing, must be of high quality (7/8 to the solar light), then more expensive.
  • Other danger : softeners in organic cotton (which is naturally a little “rough to the touch”), and any additive – often added when dyeing – such as the ones against static electricity, anti-microbial: if they contain the smallest trace of silicones, then you will have problems of adhesion after washing and of breaking of the screen inks ! Then, tests – simple or more complicated - and accurate analysis in labs must be done before printing, if you have the smallest doubt about the dyed textile and even the white fabric.
  • Hard water can also be a problem ! In dyeing, in washing after dyeing, when developing and reclaiming the screens, when preparing the water based inks ! The (even micrometric) calcareous stones can prevent a good adhesion and a good cohesion of inks or transfers, then bring a lack of resistance and elasticity of the print.

What to improve? A lot of things !
I wrote a small very precise manual about what its printers, direct or indirect must do and… not do !

  • Fifteen main points :
  1. Have good films, sharp and with good edge definition
  2. No wooden or iron frames : aluminium or selfstretching frames.
  3. Choose yellow fabric instead of white for any fine and accurate printed logo or image
  4. Use the high or very high tensions – above 25 N/cm anyway
  5. Have a light integrator on your exposing unit (metal halide lamp lateral or from the top, but NOT under – no UV tubes). Clean the lamp each two weeks.
  6. Sharpen the squeegee blades
  7. Have a better control of colours and densities

  • The respect of the seven above points is the minimum for quality
  1. Don’t put the water based inks and the plastisols in the same storage room
  2. Don’t use a spray for adhesive : use brush or even screen print it
  3. Kiss printing and one stroke only (I saw up to 5 ! Ridiculous) – choose better the fabric, ink and shore hardness!. If two strokes are necessary, flash in between each.
  4. Use rather automatic carrousel than the “long table” and manual printing.
  5. Flash or/and cure correctly the inks
  6. For high densities and some special effect, don’t use multi direct coating, use thick capillary films
  7. After printing, keep only a minimum of screens for reprint : reclaim and reuse !
  8. Treat the spoiled rejected water

The Future The pressure increases from the buyers and end users

Environmental & health constraints

  • The direct customers and the end-users put a higher and higher pressure : they want more and more green products produced in a green manner.
  • The big producers of sport-wears and other garment - here I can name Adidas, Nike, Decathlon, Puma, Quick-Silver - it's of “public and recognised notoriety" - refuse absolutely the use of plastisols with phtalates, the use of formaldehyde, (replaced by thiourea dioxide - which I am not sure it is so “clean” !). Some refuse the use of PVC. They refuse the work of children, even in India or Bangladesh, they want that the local social rules be respected, they want that the rejected spoiled water will be retreated, cleaned and reused as much as possible – this position is more and more followed now by most of Cities, States, Countries in the whole world.
  • Those companies want also that their “Directive for the Use of Chemicals” be strictly respected and controls are regularly made.
  • The use of the products dangerous for the health of the employees, here I mean the use of spray for adhesive the pallets or tables, the use of flock, is strictly controlled.

Improvements in printing quality

  • That’s a tendency – now a “must” - which I can better understand than anyone : there are more than 50 years I plead for the quality of screen printed images and marks. I saw so many bad prints and also so many rejects because the customers require quality and sometimes “high quality” !
  • The future for quality printing will be in a strict respect of the seven first points of the 15 I mentioned just before.
  • For the customers, they must send open files in PDF and not forget to attach the fonts used for the artwork and they must control on the proofs sent that the prints are exactly similar and correspond to what was expected.

Sophistication of images

  • As you know, the manufacturers of sport-wears want now to decorate their garments with more than a simple logo or text, but add some « graphic images » to make them more “attractive”. Many of them want to use their stores to sell their own “pure fashion” lines and not only “sportswear's”.
  • In the actual period of economical difficulties, this is not so evident ! Fashion lines of major companies saw – during 2009 - their sales reduce of 25% when their sales of sport-wears and equipment was increasing of 7% !
  • My conclusion, as a joke, "unemployed peoples have more time to do sport !”

Process colours or indexed colours ?

  • In this growth of sophisticated images, the « photographic images » are actually « in ».
  • The problem I saw during my audits is that only a few printers are able to print correct and fine 4 or 6 colours process images, on one hand because of the “general” problems seen above, on the other hand because they don’t know much about the colour profiles, dot gains or loss, densities corrections and compensation, dots size or shape, etc.
  • And they often, as they are obliged to use water based colour by their customers, have problems of drying of the small dots in the screen fabric.
  • Some of them, as they have sophisticated multi-heads carrousels, think that printing “indexed colours” is a better solution – true or not :
  • Easier to print ? Yes: square dots juxtaposed as bitmap objects. Colour separation ? Often extremely difficult if you don’t have a highly skilled prepress operator knowing very well both colours and Photoshop!
  • I remember a discussion I had with one of the best textile printers in the world and he said : “We discovered, two years ago that we became “slaves” of those indexed colours ! The “facility” to have 14, 18 colour press was making easy to use 10 or much more colours if not sufficient !... The speed of the press did not change of course but more films, more files work in CTS, more screens, more and longer setting are needed…!. We came back to 4 colours process images for photos reproduction… And we save a lot of money with an increased productivity”.
  • This is my feeling too of course ! Process printing is a big future in screen and digital textile printing …

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