10/02/2015
Explaining weight of paper (e.g. 20 #, gsm, etc....)
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Paper thin? Maybe not!
Understanding the weight of paper is not common sense and may be a bit confusing and seemingly conflicted. I’m going to take a run at explaining the common terms used to understand and communicate the weight of paper.
The U.S. Basis (not basic) Weights are the most confusing, primarily because the same paper can yield different values based on the “Basis Weight” applied while manufacturing the paper, and higher values don’t always equate to heavier/thicker print media. The “Basis Weight” is defined as the weight of 500 sheets of paper in its basic unit uncut size which means before being cut to ‘letter’ size or ‘legal’ size, the paper is weighed and categorized. If 500 sheets of Bond paper (17 x 22 inches) weigh 20 lbs., then a ream of paper cut to ‘letter’ size will be labeled as 20 lb. With that same thinking, if 500 sheets of ‘cover’ paper (20 x 26 inches) weigh 65 lbs., then a ream of this paper trimmed to tabloid size would be marked as 65lb. Fortunately, there is a metric measurement that is often displayed alongside the U.S. Basis Weight. The metric measurement, called grammage, is the actual weight of one sheet of media cut 1 x 1 meter square. Because the same size sheet is always being weighed, GSM or g/m2 (grams per square meter) provides a more uniform scale to judge a paper’s weight and thickness.
g/m2 in Practice – What to expect
What do different paper thickness and g/m2 represent in real life? Here is a rough translation of these seemingly arbitrary numbers into commonly occurring paper you will have bumped into before now – some small format, some large format:
• 35g/m2 to 55 g/m2: This is very thin paper. Most newspapers are printed on this paper thickness. As a reference, HP Translucent Bond Paper = 67g/m2
• 90 g/m2 to 100 g/m2: This is the weight range of most printer paper, and HP’s Coated Paper portfolio (minus HW Coated). This is the stuff you can pick up in packs of 500 sheets at the office supply store. HP Bright White Inkjet Paper = 90 g/m2
• 120 g/m2 to 140 g/m2: This range covers the paper thickness of most posters that are not meant to be used long-term. Paper with this g/m2 is sturdy enough to withstand a bit of wear and tear. Consider HP Heavyweight Coated Paper = 130 g/m2 and although it’s more durable than paper, HP Everyday Matte Polypropylene has a weight of only 120 g/m2.
• 210 g/m2 to 300 g/m2: This weight range has us moving into a thick and premium class. This collection is approaching card-stock thickness, but will likely still have a bit of a bend when held with two fingers. Think of HP Matte Litho-realistic Paper = 270 g/m2, or HP Premium Instant-dry Satin Photo Paper at a weight of 260 g/m2.
• 350 g/m2 and up: This range of g/m2 is often what people would refer to as ‘card stock’, but that can be a dangerous label. It’s not just the thickness of media that matters, but its flexibility too that matters. An example of this weight would be HP Colorfast Adhesive Vinyl WITH the liner = 345 g/m2, once the liner is removed, its 190 g/m2. HP Opaque Scrim is a fat 460 g/m2.
When you are asked “What is the thickest media I can print through a Z-series printer?” you can answer with confidence and authority, knowing the meaning of your answer: “Up to 460 g/m² depending on media type with a Z6200, Z6600 or Z6800 – or – up to 500 g/m2 with a Z2100, Z3200, or Z5200.” (They can support a little extra thickness with the ability to load single sheets.)
