Printers a users’ perspective

There are two major types  Laser  Inkjet (or bubble-jet)

Technobabble Laser Printers are peripherals that use a series of mirrors and lenses to "apply" the text or image onto an internal revolving drum. This application is accomplished by changing the electrical polarity of the drum's surface in the appropriate places. Toner, which is electrically charged with the opposite polarity of the image on the drum, is then applied to the drum and adheres in the designated pattern. Paper heated to a precise temperature is then sent past the drum, which applies the toner to the page.

Lasers From the user’s point of view, the result is generally a 600 dots per inch image  It is cheap and consequently ideal for high volume environments.  The initial outlay is high but cost per page is around 2 cents as opposed to 23 cents for inkjets.  The break-even point for black and white is around ten pages per week.

Lasers  Colour lasers require four sets of everything – drums, rollers and toner.  Most lasers for the cheaper (home use) can only be refilled up to (usually) about four times.  Replacement rollers, drums, etc can cost around $250, making $1,000 total, thus making a new printer a viable option.

Lasers  Colour laser printers are not generally considered viable for the home user because:  The colour tends to be ‘bright’ like an advertisement  The long-term cost makes ink-jets more viable.  They cannot print on ‘coated’ papers.

Lasers  The hot paper requirement of lasers has been utilised in an interesting way:  Coloured plastic sheets can be placed on a previously printed page and fed back through the printer.  The black text picks up more heat that the white paper. The plastic melts on to the black text but not the paper, giving interesting patterns (metallic gold, etc).

Ink Printers  Ink-jet printers. When a quartz crystal is squeezed, it produces an electrical current. When a currant is applied, it distorts. This characteristic is used to force the ink out.  Bubble-jet printers. The ink is heated to a vapour and thus forced out of the nozzle.  From the USER’S point of view there is therefore no difference.

Technobabble  In bubblejets, the ink is heated to over 600 o C.  It leaves the print-head at about 500 inches per second.  No wonder it splashes if it hits the wrong surface.

Ink Printers The Resolution of your printer depends on:  The number and spacing of holes in the print head (around 1,120)  The size of the holes  The speed of the paper past the head  The type of ink used  The type of paper  Photocopy papers absorb the ink, ‘wick’ it; ‘feather’ it or let it flow into microscopic crevasses.

Types of printer ink Water-based – Until recently this was the most usual but the ink tends to feather or bleed and is unsuitable for the high resolutions required in today’s market.

Types of printer ink Oil based – The droplets can be formed using very small quantities of ink, so it is suitable for high resolution printers. Expensive. Can clog, especially if the printer is not used for a few days.

Types of printer ink P-POP. A coagulant is incorporated in with the black reservoir. This is sprayed on to the paper before the ink, so coated papers are not required. The idea does not appear to have caught on and is being phased out.

Types of printer ink Phase-change inks. These are solid at room temperature and heated before ejection No feathering. However, these are unsuitable for home use since they need to be run at high volume.

Print it  For best quality, print at twice the graphic resolution only  Use coated paper – gloss, semi matt or matt – this prevents bleeding  There is no white ink, so use the whitest and brightest paper you can get.  Quality counts – use the best inks, the best paper and the best printer you can afford.

Micrograph of ink at 1440 on copier paper

on 1440 matt paper

on 1440 glossy

on HP2000 matt photo paper

Special Papers  There are a wide variety of specialty papers available –  Pre-printed for labels, certificates, parties, formal occasions, etc.  Coloured, stippled and pre-cut giving the effect of parchment, papyrus, hand-made, cloth, etc.  One allows the high-speed ink to permeate the gloss surface, giving it a water-proof finish.

Colour Gamut

Buying a Printer  Print-head built in: this is the ideal type because the holes can be machined to a greater accuracy. However, if the printer is left for more than a week it can clog and it takes an expert to clean.

Buying a Printer  Print-head part of the ink reservoir. These are mass produced and can vary slightly. However, if the head clogs, it is a simple matter to clean or replace the cartridge.

Buying a Printer  Reproduction. The colour will vary between manufacturers and between machines.  The more colours used, the better the output (usually).

Buying a Printer  Always take a disk with a photograph on it in to the shop and ask them to print it for you. Compare it with a print you like.  Look for skin tones and reproduction of fine lines (hair, etc).  Look for artifacts – spots and marks that are not on the original.

Buying a Printer  Resolution. Generally, the higher the resolution, the slower the print and the more expensive the machine and the cartridges.  As the resoloution increases, the number of holes increases and their size decreases.  This increases the chance of ink blockage.

Buying a Printer  An ink printer should be used every day or the ink may dry on the head causing blockage.  Some printers incorporate the print-head with the reservoir, thereby increasing the cost. However, for home use this is ideal because if the ink dries or blocks, it is a simple matter to replace the cartridge.

Buying a Printer  Others incorporate it with the printer itself.  This saves on replacement cartridge costs and gives a more accurate print head. However, cleaning a blocked head becomes time consuming and expensive.  Ideally, this type of printer should be used every day and never left idle over holidays, etc.