Its density is about 0.946 grams per cubic centimeter. Polypropylene is just slightly less dense than water. For polypropylene sheets, the GSM (grams per square meter) specification can be converted into an average thickness using the volume density of polypropylene. A one millimeter thick layer of PP would then have an areal weight between 855 gsm and 946 gsm. Similarly, 1,000 grams of water could produce a puddle one millimeter deep with an area of one square meter (or a circle with a radius of 0.56 m).Ī rule-of-thumb then is to multiply specific density values by 1000 to obtain the weight of a sheet that is one millimeter in thickness.Īs an example, the specific density of PP ranges from 0.855 g/cc to 0.946 g/cc. In other words, a one micrometer deep puddle of water that is one square meter in diameter would weigh one gram. Therefore textbook values of “density” or “specific gravity” are the numerically the same as the areal density for a sheet that is one micrometer thick. That’s because 10,000 micrometers add up to a centimeter, and there are 10,000 square centimeters in a square meter. One cube with one centimeter sides has the same volume as square sheet that is one meter by one meter by one micron thick. Areal weight alone does not uniquely describe the product because two completely different configurations could have the same overall weight, depending on the amount of scrim.Ĭonsider the following thought experiment: Thickness values are not so meaningful because the thickness varies locally, depending on the configuration of the synthetic underlayment. It describes the amount of polymer in the underlayment, allowing synthetic underlayment products to be compared to each other and also to other types of underlayments. Areal weight is easy-to-measure and meaningful. The units for areal weight are typically given as grams per square meter (GSM). Synthetic underlayment products are frequently characterized in terms of weight or, more precisely, areal weight, so it's worthwhile to examine what exactly is meant by the “weight per unit area”. Fiberglass Mineral Surface Roll Roofing.and gsm on our packaging, in our catalogs and on our website. You will find the weight of our papers stated in both lbs. Watercolor papers are heavier weight because of their need to hold a lot of water, versus drawing & sketch papers which are intended for dry media. It is usually a reflection of intended use. A papers weight does not necessarily reflect quality. This chart shows various papers and their common basis sizes & weights. When these two papers have the same size (one square meter), we see that the Watercolor paper actually weighs more than the drawing paper (130gsm vs.
So even though both Drawing and Aquarius II are listed as the same weight in pounds (80lbs), the master size sheets being weighed are not the same (again the drawing paper basis size is 24” x 36” and the watercolor paper basis size is 22” x 30”).
Measuring paper weight in grams per square meter (commonly referred to as gsm or g/m 2) is literally taking the weight in grams of 1 square meter of paper. On the other hand, weighing paper in grams per square meter does give you a clean, apples-to-apples comparison.
LB TO GSM PAPER WEIGHT CONVERTER SERIES
If you look at our 500 Series Aquarius II Watercolor paper, it also is listed as 80lbs, but the basis size of Aquarius II is 22”x30”, not 24”x36”, so it’s not exactly an apples-to-apples comparison. 500 Sheets of 400 Series Drawing paper (24”x 36”) weighs 80lbs. For example, drawing papers have a basis size of 24”x36”, versus watercolor papers which have a basis size of 22”x30”. The part that can get confusing when weighing paper in pounds is that not all paper types have the same basis size. If you place 500 master sheets of our 400 Series Watercolor paper in the 22”x30” size on a scale, it should weigh approximately 140lbs. For example, the basis size (or in other words, the master sheet size) of our Watercolor papers is 22”x30”. and is determined by weighing 500 sheets (a ream) in the basis size of a particular paper. The United States measures paper weight in pounds, whereas it is standard to measure in grams per square meter outside of the US. There are two ways that paper weight is measured and stated.