Understanding Paper Weight in Printing and Publishing
When dealing with printing and publishing, understanding the paper weight is crucial. This article aims to demystify the concept of paper weight numbers and their significance in the industry.
Basis Weight: The Foundation for Paper Weight
The numbers you see on paper refer to its basis weight, which represents the weight in pounds of a basis ream of that paper. A basis ream is a standard unit of measure used in the paper and printing industries, typically containing 500 or 1000 sheets, depending on the type of paper.
The basis ream is more significant than the finished size of the paper because it is usually cut after the printing process. For instance, an 8.5 x 11-inch sheet used in printing may be printed on a sheet that is 17 x 22 inches, and then cut into four smaller sheets each measuring 8.5 x 11 inches. Consequently, the basis weight for 8.5 x 11-inch copy paper is 17 x 22 inches with a typical basis weight of 20 pounds.
For book paper, the basis ream is 500 sheets, each measuring 25 x 38 inches. After printing, the pages may be cut into 16-page sections each measuring 6 x 9 inches, allowing for some waste allowance. As you can see, the basis sheet is significantly larger for book paper, leading to a thickness that is almost three times that of copy paper with a similar basis weight.
Cover paper has an even larger basis size of 20 x 26 inches, and a basis ream typically containing 500 or 1000 sheets. The weight range for cover paper is between 80 to 140 pounds, making it considerably thicker than a comparable size piece of copy paper.
How to Determine Paper Weight
While the basis weight provides valuable information about the quality of the paper, it’s essential to note that you cannot directly measure the weight of a single sheet of paper. To accurately determine the basis weight, consult an industry-standard table of trade sizes for paper. These tables provide both the basis weight and the number of sheets in a basis ream.
Grams per Square Meter: An Alternative Measurement
Instead of pounds per ream, manufacturers in many countries use grams per square meter (gsm) to specify paper weight. This metric system precisely describes the weight of a square meter of paper. For example, a 70gsm sheet means the paper would weigh 70 grams for a square meter.
Understanding the gsm can help in comparing weights across different paper types and manufacturers. Higher gsm numbers indicate thicker paper, while lower gsm numbers indicate thinner paper.
Converting Paper Weight Measurements
To convert between pounds per ream and grams per square meter, you can use an online equivalency chart. These charts provide a simple way to translate between the two systems, making it easier to compare and select paper based on your specific needs.
For example, a 20-pound paper (basis weight) is equivalent to approximately 70 to 80 grams per square meter. Similarly, 200-pound book paper would translate to around 250 to 280 grams per square meter.
Understanding these measurements is vital for anyone involved in printing, publishing, or paper selection. Whether you are a professional printer, graphic designer, or someone looking to enhance the quality of your printed documents, knowing the basis weight and gsm can significantly impact the final outcome of your project.
In conclusion, the choice of paper weight plays a critical role in the quality and durability of your prints. By understanding the concepts of basis weight and grams per square meter, you can make informed decisions and achieve the best results for your print projects.