Saturday, 6 October 2012

Screen printing refresher

I asked Mike's advise about how to manage the Indesign file to get the positives for screen printing.  He recommended I use spot colours and black to create channels in Indesign.  All colours including links need to be pure black with no CMY in.  Photoshop files can be greyscale.

This was the final design which Janet passed.

The paper I sourced from Footprint was SRA2 (450mm x640mm)  I worked out I would be able to screen print three hot dog fold books on each sheet (Each 400mmx200mm). The problem was how to print the positives.  Each could be three A3 off the Laser printers however as I was doing two colours lining the positives exactly could be nearly impossible.  
I spoke to Kirsty in Screen printing and she recommended I get the positives printed A2 by James on the ink jet printers.  When I tried to get the channels screen printed he tried but said because the inkjet printers rasterise the image first the printer would not under stand the channel information.  He recommended I split all the pantone green onto another layer then turn it black!  I did have a look at doing this however it was tricky as some of the images were links out to Illustrator and Photoshop.  With the channels the 'white' areas are automatically cut out of the coloured areas I would have to do this manually using layers.  I was fast running out of time with this so decided to try the three A3 idea.  Afer ten minutes on the light box trying to line the two colours up I realised this was a fruitless task.  Afer spending a lot of effort planning the layout of the book it could all go wrong with this method.

Mike was teaching all day so I waited until 3.30 when he had finished as no other technical staff could think of a quick solution to the problem.

The Channels on Indesign.  

True to form Mike knew a quick solution to my problem and how to obtain A2 split prints from the ink jet printers.  The answer was quite simple.

Select the channels you need to print in Indesign on the print/separations menu
Under PPD you need to be able to select A1 (Mike has to add some software to the Mac)
Printer = Postscript file

In preview save the Postscript file as a PDF.

The positives can now be printed on the Ink Jet printer!

Quick reminder on screen printing on paper, even though I have screen printed three other times it was in the first year and I had forgotten quite a lot.

1.  clean screen with d-strip and d-solve then degrease with soapy water- allow to dry.Add you name 
2.  Coat screen with emulsion allow to dry in the warm cupboards (1 hr) 
3.  Postives are exposed then excess emulsion rinsed ( Allow to dry)
4. Brown tape any yellow(exposed) areas of screen and all edges 
5. Set screen up on beds - start with lighter colours
6.  Binder 70%Acrylic paint 30%
7.  Switch vacuum bed on
8.  Pull paint across screen
9   Lift screen then draw paint away

Lessons learned already

  • Dont put top and bottom of the design too near screen edge as difficult to pull paint across screen due to frames restrictions on bed.

  • Dont have to cut out white from  colour of overlaying with balck.  Just another item to line up too.
  • Mix enough paint for whole job
  • With two plus colours dont try to put too many designs on one screen as difficult to line up especially type.
More to follow...

Took around 2 hours to print 30 A2 prints (with set up times but excluding cleaning equipment)

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