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Watercolor Paper Sizing 101: All You Need To Know Before Watercolor Painting

Without adequate sizing, pigments will get absorbed by the cellulose fibers of the paper, resulting in bleeding. But sizing watercolor paper improves its absorbency, allowing artists to play with colors. And gelatin is widely used among artists for surface sizing.

Watercolor Paper Sizing

For watercolor artists, sizing paper is as important as having the right art supplies.

Sizing is basically a technique through which the absorbent qualities of the watercolor paper are altered. The origin of this technique can be traced back to the 18th century when James Whatman invented a pre-sized wove paper with gelatin.

Because newbie artists do not know much about watercolor paper sizing, I decided to create a guide on the same.

Watercolor Paper Sizing: What Is It And Types Of Sizing?

Watercolor Paper Sizing: What Is It And Types Of Sizing
© Homesthetics - Dylla Setyadji

Sizing doesn’t mean the actual size of the paper; rather, it refers to the bonding agent used to alter the absorbency properties of watercolor papers. 

When the right sizing agent isn’t applied to the paper, a paper cannot be called watercolor paper; instead, it’s a copy paper. It’s called so because the paint is absorbed like a sponge into the fibers of the paper. In other words, it soaks through and ruins the surface of the paper. 

Taking that into account, painting on a sheet of paper without sizing is impossible because the brush strokes would tear it apart. 

So, watercolor paper sizing is important to prevent the paint from sinking right into the paper. It ensures the paper absorbs moisture at a consistent rate when working with wet media. 

Types Of Watercolor Paper Sizing

There are 3 types of watercolor paper sizing:

  • Animal sizing or gelatin sizing (traditional method) 
  • Synthetic sizing
  • Non-traditional sizing 

Properties Of Paper Influenced By Sizing

3 properties of watercolor paper influenced by sizing are color appearance, absorbency, and strength.

1. Color Appearance

Watercolor papers that are traditionally sized using the by-product of animals or gelatin aren’t bright white but slightly creamy in color. Although gelatin is a water-soluble substance and naturally transparent, it lends a slight yellow color when used on artist-quality paper. 

2. Absorbency

As I have already mentioned, paper surface sizing affects the absorbent quality and permeability. Because of sizing, paint doesn’t soak into the fibers of the paper; rather, it stays on the surface, allowing artists to work at their own pace. 

3. Strength

The third property that is altered by the sizing agent is the strength of the watercolor paper. Surface sizing– be it internal or external, lends a rough and crisp costing to the paper. This coating is what adds to the durability of the paper, safeguarding it from abrasion and wear. 

How Sizing Affects Watercolor Painting

The majority of artist-quality watercolor papers are either handmade papers or mold-made. Furthermore, they are specifically created for wet media painting, like ink or paint. 

Therefore, sizing is an important element of watercolor painting because it offers greater control to artists. A good-quality watercolor paper, along with the right sizing solution, will accentuate the finest aspects of watercolor paints, as against lesser-quality papers. 

Because of the sizing solution, the rough surface of the paper remains wet long enough for artists to work. That means the sizing agent prevents pulling colored pigments deep into the cellulose fibers. 

Remember, experimenting with colors would become impossible if the paint is entirely soaked up by the paper because it fixes the pigments in one place. In good-quality watercolor papers, artists get enough time to transfer pigments all over the surface in a wet wash. Not just that, but they also get time to remove the color from a flat surface in case it’s needed. 

Thanks to sizing, dry paints are able to settle near the paper surface. Thus, the effects of each color are heightened due to sizing, which is why the painting appears vibrant and luminous. 

Anytime an artist mistakenly applies hard or strong pigments on the paper, they don’t get absorbed into the surface. That means the pigments will slide on the surface for quite some time, preventing artists from working on the painting. 

So, the amount of sizing ingredient you use will have a significant impact on the way the paper reacts to pigments when applied in different watercolor techniques. 

How To Choose The Right Watercolor Paper Sizing

A. Factors To Consider When Selecting Watercolor Paper Sizing

Among the 3 types of watercolor paper sizing, knowing which one would be the right pick for surface sizing could be challenging for many artists. But not to worry, for I have gone into the nitty-gritty of watercolor paper sizing and shortlisted a few factors to help you decide which one you should go for. 

1. Painting Techniques

Sizing makes it easier to use paint and experiment on the paper surface. 

When artists talk about well-sized watercolor paper sheets, what they mean is that paints flow through the large sheets of paper smoothly and spreads over the surface properly. That means a well-sized paper allows artists to work with ease because the absorption properties are perfectly balanced. 

For this reason, you should always take into account the painting techniques you intend to employ on the sized paper. Remember, the sizing will have a great impact on the finished painting. 

Here’s a quick rundown of watercolor painting techniques that are affected by the sizing of the watercolor paper. 

I. Lifting Off Paint

Many artists prefer the lifting technique to complete their watercolor masterpieces. 

In this technique, paint, usually from a dried painting, is removed from the paper surface by either soaking up a few colors using a brush or re-wetting the painting. More often than not, this is done to lighten areas where there are too many pigments to correct mistakes. You can even create a sequence of lighter forms via this technique. 

Now, incorrect sizing will make it virtually impossible for you to remove paint via the lifting-off technique. That’s because a too absorbent or too soft sizing will pull the pigments deep into the fibers of the paper. 

II. Glazing

Another essential technique in the watercolor painting process is glazing. 

Adding depth to a watercolor painting by applying diluted paints in layers, and letting them dry amid application is known as glazing. In simple terms, artists apply colors one at a time in transparent or thin layers, allowing each layer to dry prior to layering another color. 

Have you ever imagined what would happen if large sheets of watercolor paper weren’t sized properly? With each new brush stroke, the layers already applied to the surface would be activated without sizing. 

That means the pigments will adhere to the fibers of the paper, and each layer will merge and blend with the other every time you try to paint a fresh glaze. Hence, on inadequately sized paper, glazing will become troublesome. 

III. Wet-On-Wet Techniques

Quite popular among beginners, wet-on-wet techniques result in spontaneous, soft, yet complex effects, when using watercolors. 

To achieve such effects, artists dip the paintbrush in water and brush it across the paper to wet it. This is done in a way to create a wash or shape on the paper, before the paint is added over the wet area. 

If wet-on-wet techniques are carried out on paper made of wood pulp, such as student-grade paper, pigments won’t be absorbed. In turn, this leads to excessive dispersion, mainly because the papers are extremely stiff. 

Taking everything into account, I’d recommend going for artist-grade papers because they are traditionally sized with gelatin. 

2. Pigment Behavior 

Not many know that the behavior of pigments is, to a great extent, influenced by the surface of the watercolor paper. 

As I stated earlier, student-grade watercolor papers are made of wood pulp, which doesn’t produce great results like other papers. On the other hand, professional watercolor, acid-free paper is made of real cotton, such as cotton paper. 

When gelatin sizing ingredients are applied to such papers, their flexibility is reduced, which is why wet media or pigments seep into the fibers slowly. So, you get enough time to play with colors. 

Be it a hot press paper or lightweight paper, bear in mind that certain papers are intentionally oversized to make up for sizing loss, which would occur during the stretching process. How a pigment would behave on a sheet of paper can be tested by dropping water droplets on the paper. 

In case the droplets pool on the surface, it’s an oversized paper; meanwhile, it’s a hard-sized paper if the droplets don’t sink into the paper and stay on it. 

3. Painting Style

By influencing the absorbent qualities of watercolor papers, sizing does affect the painting style. In this regard, I’d suggest checking the texture of the watercolor paper, which is mainly of 3 types– hot press, cold press, and rough surface. 

As far as a hot press paper is concerned, it has a hard yet smooth surface. While some artists find the texture ideal for detailing, others prefer cold-pressed or rough surface paper. That’s because the overly smooth surface of hot-pressed papers makes it challenging to control the pigments. 

Meanwhile, cold press paper is among the most versatile papers mainly because of its velvety look. In comparison to hot-pressed paper, the cold-pressed paper has a semi-rough surface, which makes it ideal for both smooth washes and detailed work. For this reason, it’s quite popular among artists of all levels. 

Papers with a pronounced tooth, ideally called rough paper, are wonderful for washes. That’s because the texture adds brilliance to the finished painting. 

4. Budget

In Asia, papermaking experts used a variety of binding agents to size watercolor papers during the papermaking process. 

For a good number of years, gelatin has been the go-to sizing ingredient for artists because it’s usable both externally and internally. However, it wouldn’t be the right choice if you have to size single sheets in bulk. 

Alkyl ketene dimer (AKD) and methylcellulose are inexpensive sizing ingredients you can use on your watercolor paper. 

Ultimately, whichever sizing agent you choose depends on the number of sheets you have to size and your budget. So, make sure to consider these two factors before you choose a sizing agent. 

B. Sizing Options For Watercolor Paper

Before I dive in to discuss the sizing options for watercolor papers, let’s discuss in brief the 3 different types of papers used in watercolor paintings. 

1. Hot-Pressed Watercolor Paper

Watercolor papers manufactured by squeezing the sheets between hot metal rollers to erase textures are referred to as hot-pressed papers. This means hot-pressed watercolor papers have a smooth surface, because of which they are suitable for artwork with finer details. 

Note that hot-pressed papers aren’t as absorbent as other papers, which is why pigments sit on the surface for quite some time. 

2. Cold-Pressed Paper

Where a hot press paper is pressed between hot metal rollers, a cold-pressed paper is squeezed between cold metal rollers to create texture. On cold-pressed paper, pigments seep into little dimples and bumps, meaning it’s far more absorbent than others. 

3. Rough Paper

As the name suggests, rough paper is one which has a rough texture, which is why it is ideal for loose and expressive painting styles. 

During the drying process, single sheets of rough paper are pressed between textured sheets to make them bumpy. Because of the rich texture of the paper, artists are able to get granulation in their finished work. 

2 Types Of Sizing Options For All Types Of Paper

Be it hot-pressed paper, cold-pressed paper, or rough surface paper, watercolor papers can be sized in 2 ways– internal sizing and external sizing. 

1. Internal Sizing

Internal sizing of watercolor paper usually occurs in the initial stages of the production process. In this method, the sizing solution (chemistry) is mixed with wet paper pulp prior to forming the sheets. 

A purpose-made synthetic wax alkyl ketene dimer is used when sizing the paper internally. While internal sizing ingredients can be used in all types of paper, they are generally applied to machine-made papers. 

2. External Sizing

Also known as surface sizing or tub sizing, external sizing is done in the final stages of the paper production process. Individual sheets of paper are dried before being immersed in gelatin solution to coat the external surface. 

As an artist, you can size the highest-grade watercolor papers like those that are acid-free. 

Some manufacturers prefer both internal and external sizing. In regard to the latter surface sizing technique, a sizing formula is applied to the paper pulp directly on the inner side. Then, the paper is submerged in an external sizing solution to enhance its durability. 

Internal sizing, to a certain extent, changes the structural qualities of watercolor papers while keeping them stable and slightly stiff. The surface texture of the externally sized paper, on the other hand, is stiff or crisp. 

How To Apply Watercolor Paper Sizing
© Homesthetics - Dylla Setyadji

How To Apply Watercolor Paper Sizing

In regards to surface sizing, gelatin from animal hides and bones or vegetable starch is most commonly used by artists. Gelatin has been preferred by artists because it improves the flexibility and strength of the paper. 

While you can use methylcellulose in place of gelatin, keep in mind that it shrinks after the curing process. That’s mainly because internally scaled pulp (paper) cast pieces may dry to form a brittle texture of the mold. Therefore, methylcellulose works like a hardener and can be used to stick sheets of paper. 

Even carboxymethylcellulose (CMC), as per papermakers, may lead to a slight plastic sheen while causing yellowing. 

External Sizing 

Although a time-consuming process, external sizing has the edge over internal sizing because different sheets of paper can be sized as per the needs of the artist. 

Unlike internal sizing, which encases each and every fiber of the paper, external sizing adds a layer to protect the surface of the sheet. Because of this protective layer, the sheet reduces bleeding and absorption. 

You can apply surface sizing to a well-dried paper using one of the following methods:

  1. Tub Sizing – Dry sheets are laid down in a tray containing the sizing ingredient, wherein they are soaked for some time. After that, the sheets are light-pressed. 
  2. Spraying – Mix the sizing formula with water, pour it into a spray bottle, and spray it onto the paper so that the sprayer doesn’t clog. 
  3. Brushing – With a large soft-haired brush, spread the sizing on the paper by applying strokes in a single direction. Apply a second coat of the sizing in the direction perpendicular to the first coat. 

Gelatin Size Recipe: Art Materials Needed

Here’s what you’ll need to size your paper sheets:

  • Gelatin
  • Sheets of paper
  • Water
  • Stirrer
  • A shallow tray
  • Support sheet
  • Blotting paper
  • Laminate pressing boards
  • Spatula

Step-By-Step Guide To Apply Gelatin Sizing On The Watercolor Paper

A 2 to 3% of gelatin solution will be ideal to size paper for watercolor painting. 

Combine 3/4 or 1-ounce of technical gelatin with 1 liter of water, preferably cold, and keep it aside until the particles of gelatin swell. After several hours, warm the mixture below 140°F and mix it well until the particles dissolve.

Once you’re done, follow the steps mentioned below to size your papers for creating stunning artwork. 

Step 1: Pour The Gelatin-Water Solution Into The Tray

Take a shallow tray and transfer the sizing solution, i.e., gelatin-water mixture, into it. When it comes to the tray, keep in mind that it should be slightly larger. That’s because your paper won’t be sized properly if you don’t use the right amount of sizing solution. And a small tray will hold less sizing solution compared to a larger one. 

Since you’re using gelatin, make sure it is warm at about 104°F for better results. 

Step 2: Take A Support Sheet And Put It Into The Tray

Now grab a support sheet and put it into the tray. Adding a support sheet is crucial because it will help you remove the sized paper from the tray, so make sure you use a high-quality product. 

Of all the sheets available, I prefer polyester web material because it is strong and durable; however, you can go for other materials if you want. 

Step 3: Open Out Book Gatherings And Submerge Single Sheets Into The Tray

Before you start immersing paper sheets, unfold or open out book gatherings so that you can submerge each and every sheet. 

When immersing the paper, place support sheets both at the bottom and on the top. Also, make sure to soak one sheet at a time by making a stack of leaves. Anytime I size paper sheets, I make a stack of 75 leaves, but you can extend it to 100. 

Whenever you size leaves in stacks, make sure to add enough size to the tray so that no leaf comes out unsized. 

Step 4: Take Out The Sheets Once They Are Drenched In Size

After immersing the sheets in the gelatin bath, wait for some time so that they get drenched in the solution completely. Once they are sopping wet, take the sheets out and blot off the excess size using blotting paper. 

However, if you soaked a stack of leaves, pull the entire stack out of the tray along with support sheets. Then, put the stack in the middle of the pressing boards and blotters after draining it before squeezing it for about a minute. 

Step 5: Place The Papers On A Drying Rack

After that, it’s time to air-dry the papers, for which you’ll have to put them on a drying rack. 

However, when placing single sheets on drying racks to air dry, changing to new support sheets is important. And in regards to the stack of book leaves, take each leaf out carefully and place them on the drying rack. But before that, cover them with polyester support material. 

Keep a spatula handy, as it will be useful in lifting the corners of the papers. 

Step 6: Allow The Sheets To Air-Dry Until They Start Curling

Let the sheets air-dry on drying racks, but make sure they do not dry completely. 

That means the sheets should dry to the touch yet be slightly damp. As for the final drying process, sandwich single sheets between felts or blotters and under slight pressure, which greatly depends on the surface finish and texture. 

Meanwhile, you can arrange book leaves into gatherings after taking them off the drying rack by pressing them in a bunch of gatherings. In the meantime, don’t forget to insert blotters after every 2 to 3 gatherings. 

You can also dampen the book leaves again after they are dried and rearrange them for the final pressing stage. I’d recommend the latter method if you have to arrange large bunches of book leaves. 

As a word of caution: throughout the process, handle the book leaves and sheets with care to ensure the surface characteristics aren’t lost.

FAQs Related To Watercolor Paper Sizing

  • What are the different types of paper sizing?

    Basically, there are three different types of paper sizing– strong sized or hard sized, weak sized or slack sized, and unsized or waterleaf. 

    Strong-sized or hard-sized papers include all the coated fine art paper used for creative purposes. Weak-sized or slack-sized paper, often referred to as soft-sized paper, includes newsprint papers along with non-waterleaf papers whose degree of absorbency is relatively high. 

    Finally comes unsized paper or waterleaf paper, which includes filter paper and blotting paper. 

  • What are the benefits of sizing paper?

    As the sizing ingredient envelopes the cellulose fibers of the paper, it eliminates or reduces bleeding to a great extent. Furthermore, sizing keeps the paper safe from oxidative breakdown, meaning the paper won’t turn yellow

    Unlike other fillers that weaken the paper, sizing adds strength and adhesive qualities to it. 

  • What is a good weight for watercolor paper?

    Weight of the paper is one of the most crucial factors that artists need to consider during watercolor painting.  Gram per square meter is the unit in which the weight of watercolor papers is measured and watercolor papers are available in various weights from 90 GSM to 300 GSM. 

    While 90 GSM papers are well-suited for drawing techniques, they cannot be used for heavy watercolor painting. Meanwhile, 140 GSM papers are better, but keep in mind they may buckle if used unstretched. 

    On the other hand 300 GSM papers are heavier than others, which is why they are ideal for soaking and heavy wash. Though their price is slightly on the steeper side, they are resistant to buckling. 

  • How can I stretch watercolor paper before painting to prevent buckling?

    The benefits of stretching paper are aplenty, from eliminating buckling to allowing the watercolor paper to lay flat on the surface. 

    Traditionally, a watercolor paper was stretched by immersing it in water for about 20 minutes. After that, it was stretched and fastened to a lightweight ply backing board (braced). As soon as it dries, it compresses to a tight flat surface. 

    I prefer stretching watercolor paper by spraying water on the rear surface of the sheet, taping it with gum paper tape, and pinning it to a backing board. When pinning the watercolor paper to the board, make sure the dry side faces up. 

  • Can I use unsized paper for watercolor painting?

    Using unsized watercolor paper for painting is advised against as such papers get damaged pretty easily because of their soft surface texture. Moreover, the finished artwork won’t be as good as it would have been on a sized watercolor paper. 

    Even then, however, if you wish to use unsized watercolor paper, you can lay the paper flat and apply gesso (acrylic primer) to prime it. 

  • Can I add sizing to the watercolor paper after it has been made?

    Yes, you can add sizing to a watercolor paper after it has been manufactured. Such sizing is known as external or surface sizing, wherein you size the watercolor paper externally to enhance its durability.  

  • What are some common problems that can arise if paper sizing is not applied correctly?

    If paper sizing isn’t applied in the correct amount, your watercolor painting will appear patchy when you apply a wash of color. In addition to that, watercolor paper with incorrect sizing will have splotchy or grease-like marks on the surface. 

    The good news is that you can correct the paper sizing by immersing it in water and cleaning the paper surface. Because of this, surface sizing is dissolved and dispersed across the surface. Plus, greasy marks are washed away due to soaking and brushing the paper. 

  • What are some recommended brands of watercolor paper?

    Some of the best brands of watercolor paper in the United States are as follows:

    • Fabriano
    • Strathmore
    • Canson
    • Arteza
    • Arches
  • Tip

    Always go for heavier-weight paper when it comes to watercolor painting because they do not require stretching. Furthermore, they absorb water better than lightweight papers and won’t wrinkle or buckle when wet. 

    On a heavier paper, you can try new brush strokes or techniques for polishing your skills. 

    Conclusion Of Watercolor Paper Sizing
    © Homesthetics - Dylla Setyadji


    To sum it up, watercolor paper sizing is crucial before getting started with watercolor painting, as it improves its absorption capabilities. Watercolor paint tends to bleed on unsized papers, but artists get more time to play with colors on a sized watercolor paper. 

    Some paper manufacturers size watercolor paper sheets internally during the printmaking process, while others do not. In such cases, you’ll have to size the paper externally using gelatin to enhance its absorbency. 

    Instead of soaking the paint pigments, sizing ensures pigments sit over the paper surface, refracting color brightly. Also, anytime you choose a watercolor paper for your projects, always check whether the paper texture is completely smooth or slightly rough.