What is gsm and which paper gsm should you look for when you’re choosing paper? When I was a beginner I didn’t understand this and would pick the wrong paper which wouldn’t be suitable for watercolor painting. I ended up needlessly wasting good paper.
GSM is the acronym for ‘grams per square meter’, and in general about 200gsm paper should be suitable for most watercolor painting. Anything under is likely to buckle and warp when painting heavy washes.
In this article I’ll explain everything about gsm and what you need to know to pick the right watercolor paper for you. I’ll also test out some of the most popular watercolor paper brands and some non-watercolor paper pads that could be suitable for painting, that might also be a bit cheaper too.
What Does GSM Mean?
GSM is a measurement used in the print industry, which is applied to paper in general, not just watercolor paper. The measurement in actual fact doesn’t measure thickness, but mass or weight.
As I explained, gsm means grams per one square meter. Paper is usually measured in grams. So if you take a square meter and measure the grams for that square meter, the gsm value will be the same as you change the thickness and even length or width.
So different thicknesses can have the same gsm. However it can be confusing because heavy papers tend to be the thickest.
Can that be right? Yes it can! Two papers could have the same gsm of 300gsm, but can be made differently, for example cotton paper and non cotton paper. They could then have different thicknesses, but they’re still the same weight.
What Does Pounds per Ream Mean?
Watercolor paper is also measured in lbs or pounds per ream. The lbs of the paper is usually displayed alongside gsm. This is done by measuring a ream of 500 sheets (22” by 30”) of paper in pounds (lbs).
Some standard watercolor paper weights are:
- 190gsm (90lbs),
- 300gsm (140lbs) like Arches,
- 365gsm (260lbs)
- 638gsm (300lb) which is super expensive for my wallet!
Heavy paper can absorb more water and doesn’t need stretching. When I can afford to, I get the heaviest watercolor paper available. This means I don’t need to stretch the paper.
Although if you make heavy washes you may still need to stretch your paper and mask it down. 140lb of paper doesn’t really need stretching, but some masking tape will suffice. Anything less, requires stretching.
The only reason I then use the masking tape is for the white frame border that makes the painting look much better.
Is 120 gsm Paper Good for Watercolor?
You’ll find that most printing paper will have a gsm of between 60 to 120gsm with 80gsm being the standard.
But can you use printing paper for watercolor paper? Well yes, but it would not be very good or enjoyable to paint on. Printing paper is entirely too light and thin to take lots of watercolor washes.
Here I tried to use the least amount of water I could get away with to apply a wash of watercolor paint onto the printing paper.
Even just that one wash resulted in buckling. The integrity of the paper rapidly dropped, and I am certain a harsher brush stroke would rip the paper.
So let’s try it!
Well that didn’t work out well! Printer paper just isn’t heavy enough to absorb and hold that amount of water.
Look at all the blotching. Watercolor paper is treated in a process called sizing. This let’s the paper avoid any blotchy effects like in the photo above.
I would advise using printer paper only for sketching and pencil lines. If you have spent a decent chunk of time penciling and then paint over, it will end up all for waste.
So to preserve those lines when you have a finished piece, use a light pad to transfer the lines to good quality watercolor paper, and then paint over.
Is 200 gsm Paper Good for Watercolor?
Any paper weight over 170 gsm is called board, generally because of how thick it usually is. So 200gsm is really a great weight of paper to use for watercolor painting.
Most affordable watercolor paper pads are available around 200 gsm weight, obviously getting more expensive as you increase the weight.
My Moleskine Watercolor Sketchbook is 200 gsm and is my favorite watercolor pad to take for travel and outdoor painting.
As you can see, the paper has held up well after painting. It actually held up well during painting. The paper does take water well and there is minimal warping.
Bear in mind, with a pad like this, I don’t stretch it beforehand or mask it down. I do use masking tape, but just to preserve a white border when I’m finished painting.
The watercolor pad is around A5 in dimensions, so it’s quite small, this does have a little effect on the warping, as the smaller the canvas you work on, the easier it is to mask down and reduce buckling.
Can You Use Normal Paper for Watercolor?
Normal paper usually refers to printer paper, and as I briefly explained, standard printer copier paper is usually too light.
But what about other paper weights below 120gsm?
35-55gsm paper is super thin paper used by newspapers. If you’ve ever spilt coffee on a newspaper you’ll instinctively know it’s useless for watercolor painting.
80gsm is standard printer paper and is again still too light. 90-120gsm is better quality printer paper.
Above 120gsm can be considered ‘light card’ in the printing industry. 150gsm and above is in my experience acceptable for watercolor paper, but for light watercolor washes. I have found that 200gsm is the sweet spot for most watercolor painting.
As always I hope you are better equipped with the knowledge to know what gsm paper is best for watercolor painting. You are now armed with some vital information when choosing the right watercolor paper for your painting needs.
I would now recommend you check out my article on watercolor paper and how to choose from different brands.
If you have any more questions do pop down in the comments below and I can reply back directly.