Saturday, 12 October 2013

RESEARCH: INKS & PRINT SETUP

Choosing the right type of ink to print with can depend on the stock as well as the type of print; black and white printing, photograph printing and full colour graphics.  Opposed to industrial oil-based/alcohol inks they're more ecologically friendly.







Inks:


Ink; A liquid or paste containing pigments or dyes to colour a surface and produce a text, image or design.


Thick inks are used for lithographic and letterpress printing, whilst thinner inks are used in pens, etc.


Ink Types:


Ink formulas usually/can consist of the following:


Colourants - Pigments/Dyes

Fluorescers
Vehicles (binders, i.e. for screen printing)
Additives
Carrier Substances
Solvents
Resins

Inks usually fall into four groups:


Aqueous

Liquid
Paste
Powder

Colourants:

Pigment inks are used more than dyes because they are more colour-fast.
They are more expensive, less consistent in colour, and have a smaller range of colour than dyes.

Pigments:

Pigments are solid, opaque particles suspended in ink to provide colour. 
"Pigment molecules typically link together in crystalline structures that are 0.1–2 µm in size and comprise 5–30 percent of the ink volume." 
The type of pigment used can affect qualities such as huesaturation, and lightness of a colour.

Dyes:

Dye based inks are more suited to desktop, professional, colour and digital printing.


"Dye-based inks are generally much stronger than pigment-based inks and give more colour (of a given density per unit of mass). 
Because dyes are dissolved in the liquid phase, they have a tendency to soak into paper, making the ink less efficient and potentially allowing the ink to bleed at the edges of an image. This is why allowance in design is allowed for bleeding when sent to print.
Dye-based inks are made with solvents that dry rapidly or are used with quick-drying methods of printing, such as blowing hot air on the fresh print (i.e. laser printing).
Special paper coatings and thicker, harder papers are often suited to this ink and used more often in non-industrial settings, such as inkjet printer inks. 
Another technique involves coating the paper with a charged coating. If the dye has the opposite charge, it is attracted to and retained by this coating, while the solvent soaks into the paper. 
Cellulose, the wood-derived material most paper is made of, is naturally charged, and so a compound that complexes with both the dye and the paper's surface aids retention at the surface. Such a compound is commonly used in ink-jet printing inks." Ink#Colorants

Screen Printing Ink:
Screen Printing used ink which is acrylic based ink mixed with a binder to add fluidity. This allows it to be easier to mix colours which are appropriate to a specific need, and allows prints to be produced cheaply.
Inks can be used on paper, card, cardboard, wood, tissue, and textiles making it versatile and a viable option many designers use.

Letterpress:

Letterpress printing generally uses (linseed) oil based inks to print as it prints better. These are also called 'relief inks' . Some professional printers however choose to use rubber based inks as they can be kept for longer and don't dry as quickly.

"Modern Commercial Inks
Many commercial inks nowadays, though not all, have vehicles based on a rubber or wax compound,  which would have  problems for amateur users. They would not be very mixable with traditional linseed oil based colours for example. Commercial ink ranges  often have attractive fluorescent,  pearlescent and other fancy effects,  but careful tests on the job paper would be needed by any amateur.  Inks for big printers will sometimes be for exotic drying systems and be totally unusable by amateurs." - happydragonspress

Oil-Based Relief Inks for Letterpress
Lino & Block Printing:

Acrylic or Specific Inks such as 'relief' or 'block printing inks' such as the ones available by Daler Rowney are used due to the ease of drying and mix-ability. 






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Print Set-Up/Adjusting Colour for Print:
The scanned in pages below explain Four Colour Tints in digital print set-up. 
It explains the tints of colour using CMY and K.



Taken from fundamentals of graphic design.

Various other techniques can be used to adjust colour and correct the output of inks using a printing process. It can also produce other effects such as ink trapping and over printing.
Ink Trapping:
The adjustment of areas of coloured texts or shapes to account for misregistration on the printing press by slight overlap. This is important for screen printing, especially CMYK. 
This is required because half tone dots which make up printed images overlap when they are different sizes/angles on the screen. Therefore colours are overlapped to prevent the appearance of white gaps where they are supposed to meet. 
Ink Trapping is not necessary for photographic printing processes. 
Trapping is important on black text because the fineness, normally, of the text means it's hard to register with its surrounding colours. If not trapped, then the text can appear unregistered or blurred to read.

Overprinting:
This happens when ink overprints on another in the printing process to create another colour. This can create different colours when printed, when you have standard CMYK ink for example in home digital inkjet/laser printers. 
According to colour theory, overprinting pairs of the three subtractive primary CMY process colours produce additive primary colours. 
To overprint effectively the designer needs to keep in mind the order the process colours print in, C, M, Y, K in order to gain correct colour and registration for print.


2 Colour Overprint.



3 Colour Overprint.
Bouncers and Shiners:
A method of printing colour that results in a darker, richer black. 
When large areas of black are required to be printed it is advised to use a cyan shiner. This is typically 50/60% cyan behind the black that helps improve the visual density and saturation.
Cyan is the most appropriate out of the process print colours as a shiner, because yellow and magenta result in a 'muddy' or artificially warm black being printed.

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