What Makes Paper Turn From Brown To White?
Being flattened wood pulp and such, paper is naturally all shades of brown.
It’s processed and bleached to the desired colour using a cocktail of chemicals, depending on the finished shade that the manufacturer wants to achieve. But how come the desired colour usually happens to be white?
Generally speaking, (and setting aside the manufacturing process for now), paper is pale because the most widely available inks throughout history tended to be black. Combining the blackest ink with the whitest writing material creates the starkest contrast, which makes text easier to read.
Essentially, like any human invention, using black ink on white paper is all about making life that little bit easier. And whenever life can be made easier, then market demand generally follows – and so we end up with widely accepted traditions, like everyone using black ink on white.
A brief history of ink
Historically, inks were created by combining binding agents like shellac (bug resin), animal glue or gum arabic with dark solids. These dark solids formed either dyes or pigments, using sources like iron or lampblack (soot).
Materials like soot are high in carbon, which is great for making a dark lasting mark once it’s sealed off with a binding agent. And, being a cheap waste material and all… well, nobody was really using soot for much else.
Often when you see historic texts and their murky-looking inks, the muddy colours you see now were actually black when they were first put to paper. Over time, the organic or metal ingredients in early inks (like iron gall, the successor to lampblack) often became discoloured, or the acids in them discoloured the paper itself.
A brief history of paper
Paper first appeared in ancient Egypt in the form of papyrus, (created from plant stems), alongside the use of parchment (animal skins). The idea was developed further in China through the watery, mish-mashy combination of bark and rags. Over time, the whole concept became standardised through increasingly refined production techniques, before the idea finally travelled west into Italy and the rest of Europe.
Combined with the invention of the Gutenberg printing press in the mid-1400s, and its ability to reproduce text quickly and mechanically, the demand for paper would have increased exponentially.
Twinned with the expansion of mechanical know-how during the Renaissance and the Enlightenment, the use of paper became ever more widespread across both the Old World and the New as it grew faster and cheaper to produce.
By the end of the Eighteenth Century, the French chemist Bertholett had pioneered the use of chemicals to bleach paper whiter. During the Industrial Revolution in the decades that followed, new mass-production techniques saved more and more time in the creation of paper from bleached rags – until by the mid-Nineteenth Century, the mass-production of wood pulp (first mechanically and then chemically) led to the development of paper as we know it today.
Moving into the Twentieth Century, new-fangled innovations like electricity and automation made the whole process faster and cheaper than ever. This led to a rise in specialised grades and qualities, ranging from cheap newspaper stock right up to thick, high-finish card for luxury items.
White paper and the printing process
So how is modern paper actually made for the digital printing process?
Well, a lot of paper is actually made from the waste wood produced by sawmills. This raw material is broken up in giant tumbling drums at paper mills, and then washed, shredded and ground into small wood chips as it travels along a series of vast conveyor belts.
These wood chips are processed down further into a wet mulch. They're then bleached and essentially cooked in strong chemicals, which separates their useful cellulose plant fibres from the non-useful lignin contained in the wood.
The wood pulp needs to have its tiny fibres separated so that it can be reformed and dried into smooth, useable sheets. This separation process can be either chemical or mechanical, but it’s the substances used in the chemical separation process that first lighten the wood pulp into a paler tone.
During the manufacturing process, this fine wood pulp is bleached or dyed further to create its final white or coloured finish. The process can also involve the blending of different pulps to create varied textures, weights, strengths and smoothness in the finished stock.
The result is a kind of bleached wood-mush soup, made up of interlocking cellulose fibres, which can then be sprayed out to dry as paper in its raw form. This raw paper is flattened, stretched and dried out completely along a series of heated rollers, which finally press down the processed paper into vast continuous sheets that end up… well, paper-thin.
These vast rolls are cut down mechanically into smaller rolls, which can then be trimmed (on automated production lines) into countless sheets of the standard stationery sizes we all recognise.
And there you have it – the journey from timber to minced-up wood mush, to pearly-white printing paper! We hope this article helped to answer some of your questions about the paper making process, and why finished paper most often tends to be white.
But what about kraft and recycled paper? What's different about them, and how are they made? Take a look at our next explainer article to find out more!
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