Printer Ink Question Posed By 12 Year Old....

[KristalB]

My sons just asked me this question while I was replacing my black cartridge in the printer and I really can't answer it. How does the printer lighten colours if there is no white ink? Any ideas?

[factor-fiction]

Do you mean shades of grey or colours such green or pink?
I assume the lighter shades of grey are made by reducing the amount of ink per square micrometre

[factor-fiction]

So for light grey it leaves more gaps (which appear as tiny white spaces between the black dots) leaving the appearance of light grey text.
But as to how it would print white text on dark paper, I don't know

[weecalf]

Telll him I don't know either

[Tuvok]

There are 4 inks cyan, magenta, yellow and black. (Some printers may have addition inks such as light cyan etc.)

Every colour is made from a combination of these 4 inks.

If you have photoshop or similar, look at the colour swatch settings - play with the cmyk values an you will see the difference.

[wolf63]

I always wondered how you get white print on black/dark paper

[woofgang]

to print white text on a coloured background, it prints the background and not the letters, assuming the paper is white. A standard printer can't print white text if the actual paper in the machine is coloured.
Paler colours I think are achieved by putting less ink on the paper.

[factor-fiction]

maybe it doesn't work, wolf- I've only ever tried getting white ink on white paper, and that obviously works

[douglas9401]

I like his thinking. :)

[KristalB]

just come back to this -thanks for responding folks. An interesting concept but I think factor-fiction may have nailed it. Though hang on -that concept only works if the paper is white. If you wanted to print a series of shades of red squares -from crimson to pink -on a pale yellow or blue sheet, then surely the colour would be more orangey or purpley the paler it got?

[joko]

yes, the yellow will change the colours.

the ink soaks in a blends with the paper, it does not sit on the surface - unless its photo paper, ad even then the colour will show through.

its a dot matrix - a bit like some op art images and pointilism

[Buenchico]

Never allow 12-year-olds to ask you questions about colours. I've been trying to find a nice concise answer to this one for 40 years and I've still not found it!
http://www.theanswerbank.co.uk/Science/Question140971.html
(That's my first ever post on this site, BTW).

However, to try to answer your question:
There are two ways of creating colours. In a TV set, for example, an 'additive' system is used, where the screen starts off black but then red, green and blue are mixed to produce the colours that are required. But printers use a 'subtractive' system, where all colours are initially present (as part of the spectrum of white light that is reflected from the paper) but then those that aren't needed are filtered out. By limiting the amount of filtration (through the sparse application of inks) it can be arranged that blue is the predominant colour left but there's also enough of the rest of the spectrum present to make up a certain amount of white light, resulting in the viewer perceiving the mix of frequencies as 'light blue'

Chris

[joko]

if you know your printers dpi, that means dots per inch - better printers have a higher amount of dots, so the finished image is smooth and clear and you cannot see the dots - with a cheap or old printer on a draft setting you will possibly be able to see the dots.

the light bits of an image are just the white paper showing through more as less ink has been put on it.