OUGD505 - Creating positives for screen printing

Creating positives for Screen Printing

Part 1 

Threshold layer simplifies layer making it into block colour
Hue and saturation allows us to see the colours that will be used in screenprinting 
Another layer can be applied over the top 
An adjustment layer affects all layers below the adjustment layer e.g background 
Click alt j or right click layer and click release clipping mask to only let the adjustment layer affect one layer beneath it 
Using the multiply blend mode allows you to see how the two colours will work together e.g. how they blend over one another - overprint.
Knocking out means that space is left underneath for another colour to fill the space left by the first layer
Select shape / area and delete it to knock out a section allowing room for the other colour to be printed in this space
Photographic images can be adjusted using the threshold layer or high contrast or half-toning 
Half-toning is made of different sized dots which are solid black 
Things to consider for half-toning:
The frequency - measured in lines per inch (50lpi max)
Angle - for one ink 15 degrees this avoids moire patterns which are optical illusions
Halftones can be dots or lines of varying thicknesses 
Visible half-toning (large dots) can be used for aesthetic value 
There are different methods for the two printers in the building, black and white laserprinter or the inkjet printer in Digital Print 

Half-toning 

For the laserprinter:
In Photoshop 
Mode of the image has to be greyscale
Make any relevant adjustments
Save as a tiff file 

In Illustrator 
File New 
Place image in file
Print options
Output to be seperations
Only black ink output 
Halftone frequency angle 15 degrees

Bitmap technique for large format
In Photoshop 
The image has to be greyscale 
Then choose bitmap 
Resolution 1200
Click Halftone screen
Submit this 
frequency 40 and 15 degree angle
Can choose lines or dots and other shapes

CMYK images

Photoshop 
Channels near layers 
Showing one channel black and white 
Showing more than one channel shows how the colour overlaps
Each channel will become a different positive to print a CMYK image

Illustrator 
File print 
Black and white printer
Output seperations
Illustrator will recognise that there are different colours 
Would have to halftone all of them 
Angles need to be rotated to different ones for each colour 15 degrees, 75 degrees, 105 degrees, 155 degrees

Low resolution images are fine for screen printing if using half tones

Spot Colours

In commercial print we can print in CMYK and Spot colours 
Spot colours are specific ready mixed inks 
The Pantone reference colour system is made up of spot colours 
If done in CMYK there may be slight differences in each print whereas spot colours are consistently the same
Spot Colours can be cheaper and can allow you to use interesting inks e.g. fluorescent, metallic etc.

Photoshop 
Click colour filler
Then colour Libraries
Type in Pantone number (no field just type)
If the mode is in CMYK it will convert the spot colour into CMYK 
New file 
Mode Greyscale 
Click icon in top right of channels palette 
Click new spot channel
When creating spot colours for screen print just use a colour similar to something you want as the colour will be made when you mix the ink 
Need to save as a tiff or psd file 

Part 2

- The Blue Note Record Label, Prestige and Columbia - Record cover albums showing techniques practiced

Duotone Images

In Photoshop 

Image Mode 
Image has to be Greyscale
Click Duotone...
Click colour picker to change colour 
Or Colour Libraries for Pantone
Pantone Solid Coated 
Choose colour
Cancel
Open Duotone again 
Click Duotone rather than monotone
Can add another colour
Click box with line through it, this allows the colour to be adjusted. It changes how the spot colour is mapped. The points / ends can also be dragged up and down. Have to keep clicking ok to preview.
A duotone is always editable even after saving  
Have to save asa Photoshop file

In Illustrator

Colour Picker, Colour Palette and Colour Swatches

Can use the colour picker or colour palette to add colour
Click arrows on colour palette allows CMYK to be adjusted 
Colour block at the top allows access to the colour swatches which allows the same colour to be picked each time 

Discarding Colour Swatches
Click swatch panel 
Click swatch menu 
Click Select all unused and delete them 
If view swatches as a list it tells you more details about each colour
Only use registration colour if using for printer marks. It looks like black but isn't.
Click swatch menu then new swatch 

Adding Colour Swatches
Creating swatches from existing colours
Make sure nothing is selected
Then click the swatch menu 
Click Add Used colours 
You can edit a swatch by double clicking the swatch 

Global Swatches
Swatches made in this way are Global although other swatches can be changed to global by ticking the box
A global colour does not allow the CMYK to be changed in the colour palette but tints can be created from that colour on the colour palette
To change a global swatch double click it 
Click preview allows you to see how the new colour will look and updates everything that is in that colour 
The same can be done for tints if the preview button is clicked

Spot Colours for print 
If using spot colours can only use swatch palette
Click swatch menu 
Click Open swatch library
Click Colour Books 
Click Pantone uncoated
Shows all swatches in that book 
Type in reference number to find Pantone colour
Pantone colours are spot colours and Global colours 

Spot colours for screen printing
Click swatch menu and new swatch 
Change colour type from Process Colour to Spot Colour
Name each colour 

Click print, output, then separations shows the different inks that will be printed 

For Knocking out 

When colours are spot colours within Illustrator they are printed as separate colours 
Window separations preview allows you to see a preview of how it will print
Click overprint 
Check colour layers to see how each will print
Illustrator automatically knocks out colour , it bases the output on the spot colours available

For overprinting
Window Attributes palette
It is a object specific tool 
Click a shape then overprint fill 
You can then view the effect in the separations panel
Overprint preview must be ticked in the separations panel  
This is only used for creating positives for screen printing 

Adjusting images in Illustrator
Can apply spot colours to photoshop images within Illustrator
They have to be greyscale
Just click the image and select a spot colour from the swatch library
A tint is always a halftone colour which means that only a fraction of the colour is printed
Window Links
Links allow you to adjust images across platforms 
Click edit original to do this 



Indesign and spot colours
Whenever an image is placed into Illustrator or Indesign from Photoshop it carries across the spot colours with it
In Indesign click swatch menu 
Click New colour Swatch 
Change Colour mode for relevant spot colours
Click text to colour in a spot colour, need to click t for text at the top 
In Indesign a greyscale image can be duotoned by applying a spot colour over the top

All these techniques can be applied to Risograph printing