if paper comes from a tree, why is it white/?

Answer 1

It's bleached.

Answer 2

Paper comes in all colors as you know. At the paper mill they either dye the pulp or in the case of white paper they bleach it.

Answer 3

the pigments in the tree are coloured so during the preparation of paper a type of chemical is used to bleach out the chemical(chemical pulping)

Answer 4

because during the manufacturing process, dye or a type of bleach is added into the pulp mix. in case of diferent colour paper the wet pulp mix has a powdered colour added to it

Answer 5

Paper is usually bleached! xx

Answer 6

All the pigments in the wood pulp are destroyed with bleaching agents, leaving it white.

Answer 7

It is bleached white.

Answer 8

Haha. That reminds me of when Karen from Mean Girls asked Cady...

"If you're from Africa... why are you white?"


Gretchen - "Ohmygod, Karen! You can't just ask someone why they're white!"

lol.

I dunno why....


The paper makers are probably "paperists" against BLACK PAPER! hahahahaha

Answer 9

Fiber processing/pulping
1-Wood or plant cell walls are composed of fibers bound together. During pulping, these fibers are separated from each other and carbohydrate surfaces, primarily cellulose or hemicellulose, are exposed. Hydrogen bonding between these carbohydrate surfaces gives paper its strength. Fibers can be separated chemically, mechanically, or via a combination of the two.
1-1-Chemical pulping
The purpose of a chemical pulping process is to break down the chemical structure of lignin and render it soluble in the cooking liquor, so that it may be washed from the cellulose fibers. Because lignin holds the plant cells together, chemical pulping frees the fibers and makes pulp. The pulp must be bleached to produce white paper for printing, painting and writing. Chemical pulps tend to cost more than mechanical pulps, largely due to the low yield, 40-50% of the original wood. Since the process preserves fiber length, however, chemical pulps tend to make stronger paper. Another advantage of chemical pulping is that the majority of the heat and electricity needed to run the process is produced by burning the lignin removed during pulping.

Papers made from chemical wood-based pulps are also unhelpfully known as woodfree papers.

The Kraft process produces especially strong, unbleached papers that can be used directly for bags and boxes but are often processed further, e.g. to make corrugated cardboard.


1-2- Mechanical pulping
There are two major mechanical pulps, thermomechanical pulp (TMP) and mechanical pulp. The latter is known in the USA as groundwood pulp. In the TMP process, wood is chipped and then fed into large steam-heated refiners where the chips are squeezed and fiberized between two steel discs. In the groundwood process, debarked logs are fed into grinders where they are pressed against rotating stones and fiberized. Mechanical pulping does not remove the lignin, so the yield is very high, >95%, but also causes paper made from this pulp to yellow and become brittle over time. Mechanical pulps have rather short fiber lengths and produce weak paper. Although large amounts of electrical energy are required to produce mechanical pulp, it costs less than chemical pulp.
2-Recycled paper
Paper recycling processes can use either chemical or mechanical pulp. By mixing with water and applying mechanical action the hydrogen bonds in the paper can be broken and fibers separated again. Most recycled paper contains a proportion of virgin fiber in the interests of quality.


3-Additives
Besides the fibers, pulps may contain fillers such as chalk or china clay, which improve the characteristics of the paper for printing or writing. Additives for sizing purposes may be mixed into the pulp and/or applied to the paper web later in the manufacturing process. The purpose of sizing is to establish the correct level of surface absorbency to suit the ink or paint.
4-Drying
After the paper web is produced, the water must be removed from it in order to create a usable product. This is accomplished through pressing and drying. The methods of doing so vary between the different processes used to make paper, but the concepts remain the same.

Pressing the sheet removes the water by force. Once the water is forced from the sheet, another absorbent material must be used to collect this water. On a paper machine this is called a felt (not to be confused with the traditional felt). When making paper by hand, a blotter sheet is used.

Drying involves using air and or heat to remove water from the paper sheet. In the earliest days of papermaking this was done by hanging the paper sheets like laundry. In more modern times, various forms of heated drying mechanisms are used. On the paper machine, the most common is the steam-heated can dryer. These dryer cans heat to temperatures above 200°F (93°C) and are used in long sequences of more than 40 cans. The heat produced by these can easily dry the paper to less than 6% moisture.
5-Finishing
The paper may then undergo sizing to alter its physical properties for use in various applications.

Paper at this point is uncoated. Coated paper has a thin layer of material such as china clay applied to one or both sides in order to create a surface more suitable for high-resolution halftone screens. (Uncoated papers are rarely suitable for screens above 150 lpi.) Coated or uncoated papers may have their surfaces polished by calendering. Coated papers are divided into matt, semi-matt or silk, and gloss. Gloss papers give the highest optical density in the printed image.

The paper is then fed onto reels if it is to be used on web printing presses, or cut into sheets for other printing processes or other purposes. The fibers in the paper basically run in the machine direction. Sheets are usually cut "long-grain", i.e. with the grain parallel to the longer dimension of the sheet.

All paper produced by Fourdrinier-type machines is wove paper, i.e. the wire mesh that transports the web leaves a pattern that has the same density along the paper grain and across the grain. Textured finishes, "watermarks" and wire patterns imitating hand-made laid paper can be created by the use of appropriate rollers in the later stages of the machine.

Wove paper does not exhibit "laidlines", which are small regular lines left behind on paper when it was handmade in a mould made from rows of metal wires or bamboo. Laidlines are very close together. They run perpendicular to the "chainlines", which are further apart. Handmade paper similarly exhibits "deckle edges", or rough and feathery borders.

Answer 10

Because white is right!