Paper School

Before you start your project there are a few important tips to get the best from your paper.

GSM and thickness have no correlation.  

GSM is one of the most misunderstood of all the paper terms.   GSM stands for “grams per square meter”.  Put simply a sheet of paper 1 meter by 1 meter,  weighing 200 grams would be 200 GSM.  It is often thought that all papers of the same GSM would therefore be the same thickness.  This is not the case.  Paper is made up of tiny cellulose fibers.   The weight of the paper depends on how densely packed these fibers are.

Let’s look at a 300GSM gloss art paper and compare it to a 280GSM drink coaster board.  The gloss art paper is 230 um (0.25mm) thick. It has a special clay coating called “titanium dioxide” added to it to make the ink sit on top of the sheet to give that magazine quality print.  The process to make the sheet shiny involves passing it through two steel rollers that are rotating very quickly.  This not only buffs the sheet to a glossy finish but compacts the fibers and makes the sheet much more dense.
   
The 280 GSM drink coaster board is 524um or 0.524 mm,  more that twice as thick as the art paper. It’s made up of a fluffier batch of pulp with lots of space between the fibers. It has no titanium dioxide added, which is much heavier than paper pulp. This gives it the ability to absorb lots of liquid, perfect for its roll in life.

Many printer specifications advise a maximum GSM for use in their machines.  As you can see this is completely wrong and should be changed to a maximum thickness.

 Grain Direction

Grain direction is another misunderstood term.
When paper is produced, a “soup” of water and cellulose fibers is sprayed on to a moving screen conveyor belt.  While the fibers are mixed with the water the fibers align themselves with the direction of water flow.  A lot like a canoe in a river floats parallel to the rivers flow.  When the water is removed the fibers are left with the majority running parallel to the direction the conveyor belt was moving.  This is the grain direction.

Now imagine you have a placemat made of bamboo strips sewn together.  You would be able to roll up the place matt, but only in one direction.  The stiffness of the bamboo prevents you from rolling it up in the other direction.

The paper fibers work in the same way but to a lesser extent.  Where this becomes a problem is when you are trying to fold or print the paper or card.

 When printing thicker cards consider using “short grain” cards so the card will mold more easily around the printers rollers.

You will also get a much cleaner fold if the grain runs parallel to the fold.   If the wrong grain direction is used in a booklet the pages will tend to spring open rather than lying flat.

Lastly leave your paper wrapped up and airtight.

Unwrapped, the edges of the paper start to absorb humidity and expand. This makes the paper become wavy and unusable.


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