September 19

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Watercolor Paper Weight Explained (Find Out What’s Best)

By Anthony

September 19, 2021

watercolor paper

There are a bunch of different factors to consider when choosing watercolor paper, and its weight is one of the more important characteristics.

But this can be a very confusing topic, even for artists who have been painting for a while.

In this article I’ll help you understand how the weight of watercolor paper affects your painting experience and how to make the right choices.

Let’s get to it !

Watercolor Paper Weight

A lot of “artist quality” paper is made using a traditional cylinder mould process. This is a slow method of production which ensures a uniform surface and robust quality.

And it's actually the best way to make heavier weights of watercolor paper, which comes in very handy for water-based art applications.

Paper weight is an issue for watercolor artists because of the problem of “buckling(the way the paper warps when wet).

Light weight paper will buckle a lot, whereas heavier weights of paper warp less.

So for more watery applications very light weight paper will need stretching. *

But stretching can be a time consuming process. So maybe you need a heavier grade of paper?

On the other hand, heavier weights of paper are more expensive...

So how do you know which weight of paper to choose?

* Stretching is the process of pre-wetting paper with water so that it expands. You then tape the damp paper onto a board, so that when it dries the surface contracts. The taut surface can now withstand heavy applications of water without buckling.


What does Watercolor Paper Weight Mean?

The weight of watercolor paper is a way of describing its thickness.

So when you compare weights, you’re really talking about how thick the paper is.

The higher the weight, the thicker the paper.

As you can imagine, different thicknesses behave differently when subjected to a lot of water, as is the case with watercolor painting. So finding the appropriate weight for the amount of water we typically use in watercolor painting is a key characteristic to take into account.

But the weight of paper can be expressed in two different ways:

Pounds (lbs)

Grams per square meter (gsm or g/m²)

Unfortunately this is where things get tricky. Because these two measurements are calculated in different ways, which can get pretty confusing.

Watercolor Paper lb (pounds per ream)

Traditionally, weights are expressed using the British Imperial system, in pounds per ream.

british imperial weight system

A ream is made up of 500 sheets. And the size of each standard sheet in a ream is called the “basis size”.

In watercolor painting the basis size of paper is the imperial full sheet which measures 22” by 30” inches.

basis size for paper weight

( Why this size ? Well… this actually corresponds to the size of a traditional handmade paper mould).

So the weight that you see printed on the label of watercolor paper is actually the weight of:

  • 1 ream of imperial full sheets.

or

  • 500 sheets measuring 22” x 30” inches.


The problem with the imperial unit of measurement is that not all papers use the same “basis size” for measuring a ream.

For example, the standard size of a sheet of drawing paper measures 24” x 36” inches which is quite a bit bigger than the basis size of watercolor paper. As a result, a sheet of 90 lb drawing paper does NOT weigh the same as a 90 lb sheet of watercolor paper !

Watercolor Paper gsm (grams per square meter)

To overcome this problem we now use a metric system which measures the weight in grams per square meter or gsm:

metric paper weight system


This is the weight in grams of a single sheet of paper which is exactly 1 square meter.

GSM is a much more straightforward way of measuring and comparing paper weight because it doesn't take into account the standard sizes of different types of paper.

The “grams per square meter” system always compares the same size sheet (1m x 1m).

grams per square meter

So instead of comparing apples with oranges, now you’re comparing apples with apples!

Often you’ll find both measurements are expressed. For example 300 gsm paper is roughly the equivalent of 140 lb.

After a while you will probably settle on a favorite brand of watercolor paper and a particular weight (my own preference for finished paintings is Arches cold press 140 lb / 300gsm). 

Sometimes you might come across a pad of paper where the weight is only expressed in pounds, or maybe the metric gsm method. In cases like this it’s very useful to understand the different equivalents in weight between both systems...

Watercolor Paper Weight Conversions

For convenience, here are some of the most common watercolor paper weight conversions for these two systems of measurement:

Imperial:

Metric:

90lb

185 gsm

140 lb

300 gsm

200 lb

430 gsm

300 lb

640 gsm

400 lb

850 gsm


(Remember that these are equivalents and can vary slightly from one manufacturer to another).

All this is very well, but what weight should you choose to get the best out of your watercolor painting ?

Let’s try to simplify things…

After shopping around for watercolor paper for a while you will probably notice the most commonly produced weights are 90 lb (185 gsm), 140 lb (300 gsm) , and 300 lb (640 gsm).

It’s easiest to think of these weights as “thin, medium, and thick”:

  • 90 lb (185 gsm) = thin
  • 140 lb (300 gsm) = medium
  • 300 lb (640 gsm) = thick


What is a Good Weight for Watercolor Paper

For me (and a lot of other watercolor artists) the best watercolor paper weight is:

140 lb / 300 gsm.

This weight is not too thin and not too thick. It’s just the right weight to avoid warping for most types of wet painting applications. And it’s cheaper than heavier types of paper!

Just don’t get the 300 gsm mixed up with the 300 lb paper !

But how does 140 lb paper really compare with thicker or thinner options ? For comparison, below are the answers to a few common questions:

Difference between 90 lb and 140 lb Watercolor Paper?

90 lb / 185 gsm paper might be fine for some sketching situations but personally I avoid using this weight for painting. It’s just too thin and buckles easily, which makes controlling the movement of paint on the surface very tricky.

Some artist grade paper manufacturers don’t even bother making 90lb paper !

140 lb / 300 gsm on the other hand is a good thickness for most uses.

Is 90 lb Paper Good for Watercolor?

Not really! 90 lb paper is more like the kind of weight you would want for decent drawing paper. If you’re going to apply watercolors on top of sketches, go for something heavier.

What is the difference between 140 lb and 300 lb watercolor paper?

140 lb (300 gsm) paper is a medium thickness paper that accepts water soluble media very well, but if your style of painting involves a lot of wet-on-wet techniques, or you paint large washes, you might need to stretch this type of paper beforehand.

Alternatively you could go for 300 lb / 640 gsm paper !

This is almost as thick as card and won’t buckle in most watercolor painting situations.

But it is a bit pricey !

If you can I would suggest trying both these weights. It’s possible you’ll fall in love with one or the other 🙂 Get yourself a small pad of each option for testing - for example:

Arches cold press 140 lb / 300 gsm

Arches cold press 300 lb / 640 gsm

For a quick explanation of watercolor weights, watch my 1 minute YouTube version above…

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