Lithography, or just ‘litho’ as it’s often referred, is perhaps the most common method of printing onto paper. Both CMYK and Spot colour can be used. CMYK is the name given to printing 4 colours, namely Cyan, Magenta, Yellow and Black, all coming together to display the image. Spot colour uses specific Pantone colours. The process for litho can be daunting and drawn out, it involves many steps, which each have their own dependancies and can be expensive if they are not conducted professionally. First of all, there’s the Laying out process, which is PC based.
Printing presses use large plates to transfer the image to paper, the most common in the UK is B2 size, which is slightly larger than A2. In order to make max-mum usage of the paper and plate, several items can be ‘ganged up’ on one plate. This can be incredibly complex for a designer to get his/her head around, let alone do it. Luckily, most printers do this for you.
Next up is the films. In litho printing, film is produced from your pdf or AI file on an image setter and then a metal printing plate is made from that. There needs to be a dif ferent plate produced for every colour used. So, in a CMYK job, that’s 4 plates for every full colour page. You can see how things can become expens ive if there’s a typo?
Then we have proofs. Once the films are made, proofs are produced by the printers to give to the designers to check and sign-off so the plates can be produced. These proofs are colour accurate, but can be expens ive. Many production managers and designers still want to see proofs made with films despite the rise of technology such as ‘Direct to Press’ printing which cuts out the produc tion of films and goes straight to plates.
Once the proofs are signed off, the plates are made and the print ing begins.
When would you use Lithography for your printing?
Advantages
- Superior quality
- Availibility
- Cost effective for large print runs
- Wide variety of paper stocks to print on
Disadvantages
- Can be expensive
- Lead time and turn around
- Expensive to rectify mistakes
How does it work?
Off set Lithography is a bit weird. It uses the repulsion of oil and water to transfer the image to the paper. The plates are chemically treated to accept oil based inks, and repel water, on the image areas and the opposite happens with non image areas.
A plate first contacts rollers of a clean solution or water and then is inked by other rollers. The oil-based ink ‘sticks’ to the image area. The image is then transferred from the plate to a rubber blanket. The rubber blanket then transfers the image onto the paper’s surface. This is why it’s called ‘off set’, because the plate never actu ally touches the paper.