How to keep Gouache from drying too fast - a detailed tutorial.
If you have ever painted with gouache you might have noticed how fast it dries, which in most cases is a benefit of the medium. Under normal, mild conditions, the quick-drying quality of gouache is what makes this medium easier to use than, for example, oils because, unlike oils, gouache can be layered easily. Once one layer has dried, you can apply another layer on top of it without the need to worry that the colors will blend and create a muddy mixture. Because of the high covering power of gouache, when you apply one color on top of another it covers the layer underneath it completely without showing it. This allows gouache painters to work faster and keep the shapes and colors in their paintings clean.
However, in dry climates and well-heated rooms, the quick-drying quality of gouache can work against us. When the ambient air is very dry, gouache can dry so fast that it can make it difficult to apply colors because in such conditions they can dry right on the mixing tray and on the brush even before you apply them to the paper. Artists who live in well-heated homes and desert areas where the air is hot and dry several months a year might have encountered this challenge and it might have discouraged them from using gouache.
Fortunately, there is a solution to this problem! It’s a medium that preserves the moisture in gouache paints and prevents them from drying too fast. I’ve tested it thoroughly and have gotten excellent results with it. It is a product called Winsor & Newton Watercolor Blending Medium. In this article, I will explain how you can use this medium to extend the drying time of your beautiful gouache paints.
Here is how you can use the Blending Medium.
If your gouache colors dry too fast in your storage palette you can add the medium directly to each one of the colors in your palette.
The drier the ambient air is, the more medium you will need to add to your paints. I’ve noticed that adding 1 part medium to approximately 4 or 5 parts gouache has had the best effect on the drying time of my gouache paints.
To add the medium to the paints in your storage palette you can either use a single dropper or you can pour the medium into a dropper bottle.
You don’t need to be very precise about the proportion of the medium to the paint. I usually add about 10 to 15 drops of the medium into every well of my palette box. Then I stir the paints well, using a clean toothpick for each color.
Note that most of the wells of my palette box are about ⅔ full of paint. If you have only a little bit of paint in each of the wells of your palette box you will need to add only two or three drops of the medium to each of your colors.
You can also add this medium to your white paint.
This will help a lot in keeping your color mixes moist longer. I already have permanent white mixed with the medium, so now I’ll add the medium to Zinc White. I usually add 1 part medium to 4 parts white paint.
To add the medium to my whites I use these twist-top dropper bottles. They are great because they allow you to squeeze liquids out in small amounts and they also prevent the liquid inside them from evaporating. It’s very easy to twist them open and close them.
I take a tube of Zinc White and squeeze all the paint into the bottle.
The tube contains 37 ml of paint. At least 1 ml of the paint must have stayed in the tube, so we have about 36 ml of paint in this bottle.
Now, I’ll add the medium in the proportion 1 part medium to 4 parts paint, using a syringe. Since I have 36 ml of paint, I need to add 9 ml of the medium.
Now, I need to stir this mixture very well (I will use the handle of a small brush).
Once the consistency of the paint becomes even, the paint is ready for use.
When I start to paint I shake the bottle well and squeeze some of the paint onto my mixing tray.
Now I’ll conduct a little experiment. I’ll squeeze some Zinc White from the tube and paint a small patch with it. Then I’ll squeeze a bit of the Zinc White to which I have just added the medium and paint another patch with it.
Now I’ll use the hair dryer to accelerate the drying time of the paints. After two minutes of applying the hot air to the samples, both of the thin layers have dried.
The paint squeezed from the tube has formed a thick dry film that would make it difficult to use this paint.
While the paint with the medium added to it is still in a perfect workable condition.
You will notice that gouache paint mixed with the medium is much more fluid than the paint that comes out of the tube, but don’t worry, it won’t affect your color mixing. It only means that you will need to add much less water to your colors when painting.
Storing these bottles upside down makes it easier to squeeze the paint onto the mixing tray.
Keep in mind that this medium evaporates from the paints much slower than water, so it may take longer for your painting to dry, but eventually, the medium will evaporate from the painting completely without affecting the properties of gouache. It doesn’t create any kind of film in a painting, so you will be able to reactivate your colors with water after they have dried if you need to. The medium acts just like water with the only difference being that it evaporates at a much slower rate.
If your gouache paints dry at a comfortable speed you don’t need to use this medium, but if you paint in a very dry and warm area it will make a huge difference for you.
My friend and student, Jean, has successfully used her gouache paints with the medium added to them to paint on location in the Arizona desert.
So, in extremely dry climates this medium can be a great solution for keeping your gouache paints moist and manageable.
I hope this information helps you enjoy your gouache paints more and gives you more freedom to paint in different environments!
Download my free 20-page PDF, “Everything you Need To Know About Gouache”
In this 20-page PDF you will learn:
How to decide which colors you need when you start with gouache and how you can expand your palette to make it even more effective.
What kind of storage palettes to use with gouache to prevent your beautiful colors from fast drying.
Why you need to use two whites with gouache.
How to choose the right paper and what kinds of brushes work best with gouache.
About the setup that I like using for plein air painting with gouache.
You will also be provided with many useful tips that will make your painting experience smoother.
If you want to learn more about the medium, its properties, advantages, and its alternatives please make sure to read the “Additional Information on the Blending Medium ” under the video.
ADDITIONAL INFORMATION ON THE MEDIUM
There is something you need to keep in mind if you want to add this medium to your painting toolbox.
Your paints will dry slower not only on your palette but on your paper too, which means that if you want to apply a new layer of paint on top of another layer you will need first to make sure that the first layer has dried completely, otherwise the colors will blend and might create an undesirable effect. So, if you like to paint quickly by applying one layer of gouache on top of another, you might want to avoid using this medium.
The other thing to keep in mind is that If you are a plein air painter and you don’t work in extremely hot conditions you might want to avoid adding the medium to the colors in your storage palette and only use it mixed with water in your spray bottle to slow down the drying time of the colors on your mixing tray. One part medium to three parts of water should do the job. The reason for this is that when you add this medium directly to your paints, your finished painting might take up to one hour to dry, depending on the temperature and humidity of the ambient air. This means that after finishing your painting you might not be able to turn the page of your sketchbook right away, or close the sketchbook and put it in your backpack. You would need to wait until your painting is completely dry. For this reason, I do not add the medium to the colors in my plein air storage palette. However, if you paint in a very dry and warm area, your gouache painting will not take too long to dry even with the medium added to your paints. So, testing is necessary.
If you want the color mixes on your mixing tray to stay moist even longer, you can use this medium as your water for color mixing. You can pour it into a small container with a lid and when you need to make a color more fluid you would clean your brush in water first, then dry it in paper towels, and then dip the corner of the brush into the small container with the medium and use the medium like water to make your paint more fluid. This will help keep the colors on your mixing tray moist much longer than usual.
You might know that I do not recommend diluting gouache paints to the state of transparent washes because it makes the paint layer more fragile, so this recommendation applies to this medium as well. You can add it to your paints to make them more fluid, but don’t add too much of it. You don’t want your gouache to look like watercolor on the mixing tray. If you do, the medium will eventually evaporate from your paints just like water, leaving the pigment particles loose without the binder.
The colors in your storage palette will thicken over time and you will eventually need to start adding a bit of water to them. The white however will keep its fluidity because the twist-top bottles protect the paint from evaporation.
Now, a little bit more on the medium itself. The main compound in W&N Blending Medium is Propylene Glycol.
If you can’t find the medium in your area, you can use pharmaceutical-grade Propylene Glycol instead, but keep in mind that pure propylene glycol has a 2-year shelf life, so when purchasing it online or in a pharmacy you need to ask the seller about the expiration date of their product.
Propylene glycol is a non-toxic, viscous, colorless, and practically odorless liquid that has hygroscopic properties which means that it attracts moisture from the air. Propylene glycol is used in many different industries. In the food, beverage, cosmetic, and pharmaceutical industries, it is used to absorb extra water and preserve moisture, thus maintaining the original quality of products. It stops foods from drying out. Marshmallows are one of the examples. Propylene glycol is used to make them moist, soft, and spongy.
Because of its hygroscopic properties propylene glycol is often added to acrylic paints, both artistic and industrial. It extends their drying time and provides progressive curing to a strong film.
Propylene glycol is alcohol by nature. Its properties are similar to the properties of glycerine, but unlike glycerin, it evaporates from the paint film completely without affecting its characteristics, while glycerin never really leaves the paint layer, which can result in stickiness of the painting’s surface. That’s why I would avoid adding glycerin to acrylic, gouache or watercolor paints.
Propylene glycol dissolves in water completely, so it can be added to water-based paints like gouache and watercolor. Since it evaporates much slower than water it allows you to paint more calmly in dry climates or during times of the year when you have to use the heater which makes the ambient air very dry.
Here is what Utrecht, the company that produces acrylic paints for artists, says about the role of glycols in acrylics: “Glycols act as wetting agents for pigments and also remain in the dry film for a short time after water has evaporated, allowing for gradual curing to a strong film. Without glycols, the drying rate of the paint might not be optimal, and stiff, heavy applications might split or crack.”
So glycols play an important role in the production of acrylic paints. Not only do they slow down the drying rate of paints, but they also help them dry gradually which protects the paint film from cracking.
Propylene glycol is often used in acrylic paint and acrylic retarders, but because it is water-soluble it can be used with watercolors and gouache as well.
Also, the antibacterial activity of propylene glycol can inhibit the growth of mold in paints which is great news for gouache painters because some artists experience problems with their gouache paints getting moldy.
I hope you find this information helpful. I have used pure propylene glycol with my gouache paints and it has worked just as well as the blending medium. You can get high-quality propylene glycol on amazon, but, as I said, you need to ask the seller when the expiration date of the product is.
In this 40-page PDF you will find:
Many practical tips that may help you get the most out of your plein air painting trips.
Advice on some equipment and materials that will make your life as a plein air painter easier.
You will hear my thoughts on plein air painting which might change your perspective and add something new to your experience.
And you will get a ton of inspiration to paint which is probably what you love doing the most!
The guide is packed with dozens of images and visuals, so even if you have never painted on location before you might enjoy just browsing through the colorful pages of this e-book.
