Spot colour printing tutorials can be hard to found on the internet, so here is my modest attempt at one.
Spot colour printing is made on classic offset press, but instead of using the classic Cyan, Magenta, Yellow and Black the inks used are Pantones mix.
You need :
- A graphics software (PSD, Clip Studio Paint)
- A publishing software (InDesign)
- A Pantone Guide
How to use a Pantone Guide : first you must know on what kind of paper you will print on, Coated or Uncoated, and use the related guide. Your Patone Guide is your only trustworthy reference, you can approximate colour with PSD or CSP but it’s never exactly the same.
You must choose your colours early to make your job easier. My two colours are 1788 U and 2765 U. Those two colours can be displayed on a well calibrated screen (3 white dots symbol).
1) In your software each colour must be on a different layer. I set my resolution at 1200 dpi.
2) Each layer must be converted in b&w or greyscale. Black will be printed as you spot colour, a 30% grey will be printed as the same spot colour at a 30% ink intensity.
To get a B&W picture in PSD : Image/Mode/Bitmap/50% threshold.
With CSP : Edit/Tonal Correction/Binarization and export accordingly.
Each Layer must be a .TIFF
3) Import your .TIFF layers in InDesign
4) To set them in the good Pantone you must use the white arrow. Click on the layer, create a new tone and in “Colour type” select “Spot”
5) In “Colour mode” select your Pantone family, here “Solid Uncoated”, enter the Pantone number and the layer will switch from black to your Pantone
6) Repeat for each layer.
7) Then, export your file as a print PDF. As a safeguard you can include the Pantone numbers in the file name.
8) This is the printed result. Note my colours are more dull because I used a Coated Pantone Guide and not the Uncoated as I should have (I don’t have one).
Since this layer have been exported as a 1200 dpi threshold bitmap there is no visible halftone.