GSM is for paper!
You may have seen stacks of paper with GSM information on it but a bit surprised to see it listed while shopping for curtains. GSM known as grams per square meter is actually used for not only paper density but fabric density as well. When looking at the GSM listed on curtains the higher the number the more dense it is which in return can help block more sound and possibly more light. Common thin curtains will display a GSM of around 140 which is like the same as a t-shirt. Now if you compare a cotton t-shirt to a wool sweater, one keeps you far more toasty and feels a lot heavier. Wool can have a GSM of up to 550 GSM in some cases so right there you can see what kind of a difference the two numbers have. There are varied amounts of GSM per curtain and there really isn’t a standard GSM on certain fabrics. So while manufacture A has a 300GSM curtain with velvet, manufacture B can have a 200GSM curtain with velvet. If comparing two similar curtains that don’t have GSM listed, look at the weight of the two as it may show quite the difference. A much heavier curtain can mean a much more dense use of the fabric.
Sound, sound, and GSM.
This is a obvious thought in a sense because a higher GSM is going to block more sound in most cases. Curtains with a higher density is much harder for sound to sneak in compare to low density curtains. A quieter night for you with higher GSM curtains!
Will a low GSM curtain let in light?
Not exactly. It can help in some regards to determine if light will go through but you’ll also want to look at the fabric being used and the weave. Every manufacture is different with how they make their curtains with the same fabric. Some may have a different weave, use multiple different fabrics, or have multiple layers compared to the other. If unsure always read reviews listed on the seller’s site to see if anyone’s noticed any issues with light. A much higher GSM though will have a significantly lower chance of letting in light due to the density in general.
In the end.
On the final thoughts of GSM, the unfortunate fact is that not all curtains will list their GSM amounts so trying to compare two similarly made curtains in detail may not work. While typically a higher GSM will block more sound additional factors like the weave and type of fabric being used can make quite the difference.