How to Seal a Watercolor Painting

Although it is not typical to seal watercolor paintings as they are classically displayed behind glass, many artists feel that this is more impersonal when compared to the acrylic and oil counterparts where there is usually no separation between the viewer and the art.

It is becoming more popular to use a variety of methods to seal watercolors, and no size fits all. Some galleries, museums, and exhibitions will not consider a sealed watercolor a pure watercolor and will class it as mixed media. This is important to note as the piece may not be displayed where you wish it to or it may even change the value if you choose to seal a painting.

Watercolor is probably the most ethereal painting technique, allowing for very light transparent washes of color, layering, and building the work up slowly. It is unfortunately also the most fragile paint out of the classics as it is easy to reactivate, the thinness of the layers and the surface used (typically cotton paper), makes for a combination of factors that means that a watercolor piece is by nature incredibly fragile.

This is fragility both to the environment and to any alteration that may be considered such as adding a varnish. Varnishes can affect the color saturation, hues, and texture of the paper meaning that the work may end up having a significantly different look once varnished. For this reason, we advise that you try out any varnishing technique you are considering using on a sample piece using similar colors to the painting you want to seal or a swatch card you make out of those colors. That will allow you to gauge the amount of change to expect and help guide your decision.

Many artists mount their watercolors on MDF boards or canvases as part of the varnishing process. Here we will only discuss the varnishing, however, the mounting is typically done using a clear gel acrylic medium.

The Benefits of Sealing Watercolor Paintings

  • Protects from UV light
  • Protects from moisture
  • Saves on Framing costs
  • Allows the viewer to see the work directly without a glass separation
  • Creates a different atmosphere

Although a lot of watercolor pigments are relatively lightfast today many beloved colors such as true Alizarin Crimson and Indigo are fugitive, giving work containing them in their composition a significantly shorter lifespan. Many artists bypass this by using lightfast hues, however, some prefer to use the true shades and use a seal to protect the pigment.

If you are varnishing your watercolors to mainly protect a fugitive pigment then it is of high importance to ensure the varnish you use has a high UV rating – This will vary by manufacturer and product.

Types of Products

There are a few products that are specifically designed for the sealing of watercolor work. These will however be specifically designed to work with the fragile layering and attachment of the pigment to the paper.

A lot of artists however find themselves contending with the use of products designed for other media, most commonly acrylic, but even products designed for pastels may work. To understand how to choose products we need to understand a little more about the medium and types of products available.

Firstly there are removable varnishes and permanent ones. If you haven’t read our article on acrylic varnishes we suggest reading it as it provides a lot of information about the varnishing process. Similarly to working with acrylics you can choose to add a permanent isolation coat then the varnish meaning that the work can be cleaned and varnished at a later date.

Secondly, as acrylic varnishes typically come in two forms MSA (hydrophobic) and polymer resin (hydrophilic). This is important as the hydrophilic polymer resin varnishes are water-soluble meaning that they will destroy the painting by reactivating the pigments if applied without an isolation coat.

You can apply an MSA varnish directly to the painting, though that means that it can’t be varnished in the future so as the varnish yellows and degrades – typically 100-120 years – that will also be the lifespan of the painting.

If you use an ad-hoc product such as a pastel fixative you’ll need to check that the product will not reactivate your pigments. To do this you need to read the label, and maybe ask the staff at your local art store. You’ll also want to ensure you try it on a sample.

One thing many artists do is to paint on a product such as Golden’s Absorbent ground applied to a canvas or MDF. For some reason, this technique seems to hold up better against the effects of varnish than working with fragile paper. Changing surface may however mean a significant change in the process you may wish to forgo.

Other considerations relate to the finish of the varnish – glossy varnishes will lead to increased color saturation (darker colors), whilst a matte varnish will often lighten darks. It is generally not advised to singlehandedly use a matte varnish, so if using a spray varnish you’ll typically need 2 layers of a gloss varnish followed by the matte finishing varnish.

Example Watercolor Sealing Protocol

We choose to use an isolation coat hence our protocol will consist of three main stages:

  1. Applying Archival Varnish
  2. Applying the isolation coat
  3. Applying Varnish

The reason we need three stages instead of two as is the case with acrylics is that the isolation coat is typically a soluble acrylic medium. For this reason, we need to protect the paint before applying it.

We will be mentioning some products by the brand Golden, mainly because it is available nearly all over the globe and tends to present a good trustworthy option. If you want to use corresponding products from a different brand then please check that they are designed to serve the same purpose.

Stage 1: Applying Archival Varnish

For this stage, you will need your painting, a canister of spray-on Golden Archival Varnish Gloss, and something to place under the work to protect your surface.

  1. Lay a vinyl sheet or MDF board under your painting
  2. Shake the spay bottle to make sure the vinyl is fully mixed
  3. From a distance of 1-3 feet spray one even layer
  4. Wait for the layer to dry
  5. Repeat step three and four one if you’re working with watercolor paper and twice if you’re working with a surface primed with absorbent ground.

Just to iterate – if you are working with the watercolor paper you’ll need two fully fry layers of the archival varnish and if you are working with the absorbent ground you will need three before proceeding to the next step.

Apply the Isolation Coat

For this step, you will need a brush, water, Golden Soft Gel Gloss, and of course your fully dry painting on a non-precious surface.

  1. Mix two parts Soft Gel with one part water – create the mix very slowly and gently to avoid bubble formation
  2. Use the brush to apply an even coat of the mixture – make sure the work is horizontal to avoid streaking
  3. Allow to completely dry (check the instructions on the packaging but we would normally allow a full 24 hours to allow the gel to fully harden

Apply Your Chosen Varnish

You can now apply any varnish of your choosing with any finish of your choosing. We typically recommend using a polymer varnish because of the lack of odor. MSA varnishes as we discuss in our other article have a stronger finish but are more difficult to work with. A spray varnish will have the advantage of the ability to apply thinner even coats but can be more expensive in the long run.