Varnishing, believe it or not, is an important skill, and should not be seen as an afterthought to painting but rather a part of it. It can seem daunting at first trying to work through how to do it, when to varnish, and what type of varnish to use.
Whether you are an amateur or a professional or maybe in transition to selling your art – your pieces will benefit from a layer of varnish. The type and complexity of process you choose can be tuned to your needs as an artist.
Here we provide you with a comprehensive guide to varnishing acrylic paintings. You can navigate through the subsections if you are looking for a specific answer rather than a whole overview guide. If this is your first varnish, it is a good idea to read through and form an understanding of the process before proceeding.
Table of Contents
Why Varnish Acrylic Paintings?
There are a variety of reasons for varnishing your work, and these range from the aesthetic to the functional purposes of preserving the painting.
Enhances Color Saturation
As your painting dries you might notice that the colors become duller over time. This is because the paint dries into a porous resin meaning that the surface at a microscopic level is not fully polished.
To demonstrate how a gloss enhances colors optically think about how pebbles look when wet compared to when these are dry. Most pebbles similarly to your paint have slightly porous not completely even surfaces, as they become wet the surface is coated with the glossy water which also forms an even layer around the pebble allowing the color to really shine through.
Some companies have started introducing acrylic paints with gloss medium mixed in with the pigment, to give the painting a sheen without requiring varnish. These paints are usually a little more expensive than their typical counterparts.
Not all finishes will enhance color saturation however, varnishes come in gloss, satin, and matte finishes. Matte finishes can cause problems when used on top of dark colors as matting agent are often white. More on this later.
The basic premise remains that if you varnish a painting using a gloss or satin finish you will note the increased color saturation and vibrancy as well as a more unified look to the finish.
Unifying the Surface Finish
Different pigments dry slightly differently and with that the level of gloss and vibrancy of each pigment is slightly different to the next. The differences can on occasion be very noticeable however and give the painting a less professional appearing finish.
By using varnish well, the surface of the painting should have a more unified appearance such that no part it distinctly glossier than another unless that is the desired outcome.
Believe this; there are professional varnishers that can adjust the consistency and property of varnish to the artist’s requirements and many professional artists opt to delegate varnishing to these pros.
If you are exhibiting your art, a varnished finish is sure to fetch you a few more pennies than an unfinished looking piece. Especially if there is no artistic purpose to the unfinished surface apart from you not taking the time to complete it. With that said, some great masters such as Picasso and Matisse preferred unvarnished matt finishes on heavily gessod backgrounds.
Might be better to try to achieve the desired look with a varnish however, as the longevity of the piece is significantly increased by applying the protective layer.
Protection and Restoration Potential
Apart from looking good, varnishes also have a practical aspect, namely that they protect the work from the elements, dirt, UV light among many other potential insults.
As you might have gathered, acrylic paint has strong potential for attracting and adhering to dust particles which can become lodged in the porous material making the work appear even duller as time passes. Acrylics are also soft as they dry and even a fully cured work will remain soft and vulnerable to mechanical insults. A layer of hard varnish can save a lot of pain in the long run.
Finally, if your work is to stand the test of time and somehow in three hundred years you are to be featured somewhere amazing like the Louvre, a professional art restorer is likely to have to work on your piece. This is because even the best varnishes yellow over time and unvarnished work will attract enough dust to look nothing like the original.
If you add a removable varnish to your work with an insulation layer, then the job of restoring the work will be extremely easy as the varnish can just be removed to reveal the painting looking as fresh as the day it was painted underneath. We will discuss insulation coats later.
Varnishing a painting with removable or non-removable varnish also makes it possible to clean it with ease as you can wipe any dust or surface particles away. A typical varnish can last 100 years before the varnish yellows.
Types of Varnish
A varnish is a transparent layer of harder material that adheres to the surface of the painting offering it protection and increased durability. A varnish can also affect the finish, color saturation and appearance of the product as we discussed above. For a varnish to be removable from an acrylic painting it is paired with a coat of a glossy medium termed an isolation coat. This step is incredibly important if you feel that you might one day want to restore and revarnish the work.
The isolation coat step is not important for you if painting is a hobby, and longevity beyond a certain time frame (longer than a typical human’s life span) is not of importance.
There are two basic types of acrylic varnish, Polymer Varnish and Mineral Spirit Acrylic (MSA) Varnish. Both have benefits and drawbacks, and both come in removable and non-removable variations.
Polymer Varnish
Benefits:
- Fast Drying
- No odor
- Clean up with water
Drawbacks:
- Fast drying time leaves little room for error and difficult to manage large pieces using it
- Can be difficult to maneuver
- Not as hard as MSA once dry
Mineral Spirit Acrylic Varnish
Benefits:
- Slower drying time giving more control
- Harder finish and better appearance when dry
- More flow so provides a more level surface
Drawbacks
- Need to be used with full strength mineral spirits, important to consider ventilation
- Can only clean up with solvents
- Strong odor
So, what type of varnish should you use?
We will leave that one up to you, however, recommend polymer varnishes if you are just starting out and painting in your home as the smell and mess associated with MSA types can be off-putting. If you decide on an MSA varnish read the packaging carefully, and really think about the space you are working in.
For most purposes, a good polymer varnish from a reputable brand such as Golden will be perfectly sufficient. Times where it is probably wise to consider MSA; if the piece is very large or if the it has a lot of thick impasto layers as the increased drying time can help avoid puddles of varnish.
N.B. for impasto work you may consider a spray varnish for best results, this is however out with the scope of this guide.
Gloss, Satin or Matte
This is a stylistic choice, and some artists work to perfect their varnish by mixing gloss with satin to for example still have a sheen to the work while not having it mirror glossy as the glare from lights can make it harder to see the painting underneath.
Things to keep in mind; Gloss will give the brightest most vibrant finish; the other two types can made dark colors look duller and take away from their color saturation.
For paintings that will be displayed in an ambient room atmosphere with normal lighting levels, a gloss finish should be fine. You can also experiment with this over time.
Varnishing Step by Step
We suggest reading the steps in full before beginning.
Allow the Painting to Fully Cure
While acrylics dry significantly faster than their oil counterpart, they are relatively slow to cure. Cure here means harden and shrink. A typical acrylic painting will be fully cured approximately one month after you have applied the last layer of paint.
If the work is thick, has been made with slow drying paints or had a medium that slows drying applied to it then it will take even longer – up to 3 months.
If you varnish a painting before it is fully cured, then you risk the paint cracking under the varnish and your work being ruined – your might be able to fix it but you will certainly regret it.
Isolation Coat – should you?
As we have discussed for the varnish to be removable in the future you will need to apply an isolation coat. This is basically a coat of a clear medium that then fills the pores of the paint and provides insulation form the varnish itself. The reason for this is that the methods for removing the varnish will also take the paint off but having the buffering isolation coat keeps the paint safe underneath.
We suggest doing this as it only adds 24 hours to the process and gives the painting significantly a longer lifespan.
When choosing a medium for the isolation coat keep in mind that this must be glossy as matte and sating mediums contain white particles that can reduce the brilliance of the paint, especially over dark areas.
If you are looking for a matte finish, then using an isolation layer is important for you as the particles in the varnish giving it a matt appearance can settle in the pores of the paint making dark parts especially look mottled.
A good medium many artists use is the Golden Soft Gel Gloss. To use this medium, follow these steps:
- Dilute with water; 2 medium: 1 water ratio
- Apply a layer to your painting with a clean brush
- Leave to dry for 24+ hours
If you choose a different medium check the packaging or the brand’s website for instructions on how to use this as an isolation coat. The steps should be similar.
If you have opted out of the isolation layer, then just jump to the next section.
Set Up Your Workspace
This might seem silly, but it is an incredibly important step. Your workspace needs to be clean and dust free as dust particles lodged in the varnish will surely detract from the beauty of your work.
Once the environment is dust free, place you’re painting on a non-precious surface such as newspaper, a vinyl sheet or an MDF board that is larger than the painting.
Some artists like having the work raised on top of this surface but you do not have to! To raise it you can use empty paint tins, jars, or anything else you have at hand just ensuring it is level before you begin.
Mix Your Varnish
Use a clean vessel preferably one that is specifically and only used for varnish to avoid any trapped paint particles. Wash the vessel and allow if to airdry upside down to remove all dust.
Mix the varnish you have chosen in accordance with the instructions on the packaging. Use a clean utensil to mix to avoid any particles becoming trapped in the varnish.
Mix a little more than you think you will need.
Most artists use a dedicated soft flat brush for varnishing. This is to ensure that there is no risk of cross contamination. If you do not have a dedicated brush clean one of your brushes extensively maybe a couple of times before beginning.
Apply the Varnish
Follow these steps to apply your varnish:
- Check that the surface of the painting is clean, if not gently remove any debris with a toothpick or the like
- Using your brush, only dip it ¼-/ ½ way into the varnish and wipe off the excess on the side of the jar
- Start applying the varnish in horizontal strokes parallel to one another.
- It’s better to work with very thin layers.
- Once you have applied the first layer of your varnish allow this to dry completely (follow the instructions on the packaging, could be anything between 15 minutes to a day or two or even longer) before returning to add another layer.
- Use a bright light such as a torch to note any areas you’ve missed.
- You can try covering any remaining varnish to avoid it drying out (check for your specific type).
- You might need to apply 3-4 layers before the finish looks the way you want
NB if you are working with an MSA varnish you can apply an even layer straight away and check that you have full coverage, immediately fixing any missing areas.
Conclusion
Although it sounds difficult, it will probably feel a lot easier once you have done it a couple of times. We suggest starting with a practice painting rather than your most previous work until you have the process a little more streamlined and understand how to make it work for you.
