Tuesday, 16 February 2016

What is ...Gsm & Mics?

What is ...Number 26
Regular followers of this blog will know that in the middle of the month, I publish a "What is ....? post. The article covers various aspects of paper, printing and finishing in greater depth. However, many of these subjects are complex, so these posts are only intended to be a brief introduction to the topic.

What is ...Gsm & Mics?
To those that know, this may sound an obvious question. However many people that I speak to base their knowledge on information picked up over years and is not always correct ...so read on!

Gsm is the abbreviated term for ‘Grams per Square Metre’. In the metric system,  the mass per unit area of of paper and board is expressed in this term and is also described as weight, substance or grammage (although I've yet to determine whether this is a real word!) It is generally written g/m2,  gsm, g/m² or even g2m.

As the term suggests, it is calculated by the physical weight of one sheet of paper measuring 1metre x 1 metre. In reality, no one actually folds down a sheet of paper that large to weigh it, so it is generally measured using a scaled down measure of 7cm x 7cm, on a scale such as the one pictured below
Mics - is the abbreviation for Microns, which in metric terminology is also a shortened name for Micrometre. This is a measure of the physical thickness or caliper of a sheet of paper or board. It is usually written as Mics, mics, Mi, or µm (using the classical Greek µ - mu). To give you an idea, a sheet of 80gsm copier paper would have a thickness of around 85-90microns. The measurement is made using a micrometer such as the one pictured below (measuring a sheet that is 105microns)
Both the gsm and mics form part of the specification of any paper when it is made - if you want to know more about a mill making, you can read about it here:
Posted by Justin Hobson 16.02.2016

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