Digital Print workshop

For screen printing we'll be using spot colours as they allow accurate reproduction of colour pantone reference system and because spot can reproduce colours that CMYK can't.

Method 1-  

To select and create a layer of one colour, select a section of the colour you want to select using the magic wand tool, the go to select then similar.

Method 2-

This method is more effective. Start off by going to the select bar- colour range- select the colour you want to select with the eye dropper and it selects it all. Selection preview is set to none but if you change it to white matte then its easier to change the fizziness based on what aesthetic you want. Then click ok. After this you need to put that colour on its own layer.

To do this its cmd+j

Do the same for the black layer. Always do the whole process for the black layer too because the original may not be 100% black.   

                                  

To change the orange layer to black, lock the layer with the small chess board like button (transparency) which locks the transparent pixels in this layer. 

Then go to edit- fill-contents-black

 Always do this process for the black layer too because the original may not be 100% black. 
  

To print, turn off the layers you don't want and print the one selected and vice versa.

Technique one
For printing smaller than a3.
Open the image in photoshop and first check its the right size. Then go to image-mode-and check that its set to CMYK. Then save the file as a tif or a psd ready to move it over to illustrator. Never use a jpeg when in a software process as you will lose detail.

Then click the channels option as shown above which stores colour information.

Where the channel is darker there will be more cyan ink and vice versa. 

If you select to view one or two of them it looks like this. The nest step is to take this over to illustrator. We don't actually use any vectors or anything when its there, we just use the print settings.

So, file- print.

Check that the printer is set to the right one, positives always have to be on a black and white printer. 

Then go to output in the left hang column, mode- separations

This creates one positive for each ink that needs to be printed. 

Unlike the other image that we worked with previously, this one has tones, therefore we need to know how to print these differing amounts . The way we do this is by using halftones.

On illustrator we do this by changing the frequency (number of dots) and the angles (how much the grids of dots are rotated so they don't clash when printing)

 The best outcome for screen printing is 50-65 dots per inch. 

The angles must be 15, 75, 105,155. it doesn't particularly matter what order, as long as each screen has a different angle. 

Before printing you can also go to marks and bleed and then turn on the page information, and this will tell you which page is cyan and which is magenta etc when its printed.

Technique 2

For larger than A3

For this option you can't use illustrator to separate the colours, so it all must be done in photoshop. You must create one image per channel.

By the channel bar in the top right corner click the drop down option and then click split channels.

This creates one image per colour channel.

Next thing you have to do is create half tones in photoshop. So go to image-mode-bitmap.

(This option is only available if your image is grey scale)

Set the resolution to 1200.

 Then click - use- halftone screen and ok.

That take you to this. Set the frequency to anything between 50-65 for screen print 

And the angle must be one of the 15,75,105,155

You can also change the shape and its done! 

Don't print using the laser printer though, because it adds its own bitmap, best thing for this technique is to print down at digital print.

 Examples of bitmap when added.