Should You Seal Watercolour Paintings?

Watercolour paintings are fragile by nature. Moisture on the finished painting may cause dried watercolour to reactive and run. Excess humidity can make the paper surface to wrinkle and distort, and sunlight exposure will fade the pigments within a matter of a few short months. One of the main ways to mitigate the amount of possible damage that can be caused to a watercolour painting is through sealing it.

Sealing a watercolour painting is the process by which a UV resistant sealer, typically a clear acrylic coating, is applied to the surface of a dry watercolour painting in order to protect it from mechanical or chemical damage, at least to the extent that the clear coat can protect it. Largely, this process minimises colour fading due to sunlight, as well as makes sure that, even if the paper that the painting itself is painted on might still not be completely waterproof, moisture will not cause the colours of the painting to run.

There are, however, many features to sealing a watercolour painting, some of which are beneficial, while others may bring experienced watercolour painters some pause. This being the case, it is vital to consider all of the pros and cons before we can answer the question of if it is always necessary to seal a watercolour painting.


​One of the primary benefits of choosing to seal a watercolour painting is that it is a longer-lasting, more verified form of protection than keeping it behind museum glass. Largely because, while a glass frame is sure to keep your painting safe and secure for a very long time, it is dependent on whoever inherits that painting to also know how to handle a watercolour painting.

For example, if it transfers hands to a collector who does not know that watercolour paintings need to be kept behind glass to protect from UV degradation, they might choose to save money and put it behind a plastic frame, which will not protect it suitably. Likewise, they may know the benefits of keeping it behind a glass frame, but not know that a mat board is always a necessary investment when framing a watercolour painting, and neglect to install one, allowing for moisture to build up in the frame, causing the paper to rot.

With a sealed watercolour painting, many risks may still come to your painting, as is the nature of all art conservation, but it does provide a guarantee that, regardless of whoever next handles your painting, it is at least protected in one regard from outside elements, no matter how it is framed and in what materials. As such, sealing a watercolour painting isn’t always necessary, and your painting may have a long and safe future without it, but since it does not interfere with other framing procedures, it can be a very safe precaution to take.


​However, sealing and mounting a watercolour painting does tend to remove some flexibility in the ways you are able to display said painting. Most sealing processes recommend mounting the watercolour paper on a more sturby surface, such as a canvas, so that the paper is backed by something with more tensile strength. This is not a bad idea, but it does mean that your painting is now much larger, and by extension, much more cumbersome to hang and present.

There are, however, smaller and thinner canvases which you can mount your watercolour on, which, while they’ll never be as flexible as paper itself, should be able to provide a more workable surface. It is also recommended that you use glue that is not water-based, and is reversible, so that, if the painting does at some point in its future need to be removed from its canvas mount, that process can be completed without damage being done to it. Most painters choose to use Gesso or acrylic medium for this process, though I recommend doing your research yourself, and reaching out to watercolour experts to hear from them as well.

All in all…

​One of the important things to know before sealing your watercolour painting, should you choose to do so, is to make sure that you apply your sealant in layers. Varnish typically comes in both liquid and aerosol forms, with the aerosol being the safer version should you like to skip the layering process. However, I recommend applying it in layers, since liquid might saturate and warp the surface of your painting, or cause the colours to run and details to blur to an undesired effect.

One popular method of sealing your painting is to apply a wax varnish first using a clean linen cloth, soaking the cloth gingerly in the wax varnish and then gently rubbing the wax coat onto the watercolour painting after it has already been mounted to a flat, more sturdy backing, like a flat canvas. This process creates a waterproof layer between your painting and the sealant, and also increases the reversibility of the sealing process, since it means that the varnish wasn’t truly applied to the surface of the painting itself, only the wax layer.

​From this point on, you can choose to apply your varnish sealant either as a liquid form or as an aerosol, though you should still be careful to add the layers in small amounts at a time to avoid saturation. While this is an optional process, some artists choose to disturb the surface of the varnish gently, with a dry sponge or by passing a brush over it carefully, to avoid it having a completely glossy finish, since that might come across as too artificial for a watercolour painting. It is always important to allow your varnish to dry on a level field, so that it does not run, and coats the painting evenly throughout its surface, with no thick or thin spots.

While sealing your watercolour painting is not necessary, it is a useful measure when done correctly, and can increase the lifespan of your artwork tremendously, especially against humidity or mechanical damage being potentially done to an otherwise vulnerable piece of art.