(Dit artikel is ook te lezen in het Nederlands. Klik hier)

An article about the glazing technique in painting.

You probably have heard of the technique glazing in painting. Although the term is used to describe the technique of painting in mostly transparent layers, there is much more to it than just that. In this article, I hope to give you some insight on the technique, the history and the use of glazing in painting.

A little history and introduction.

We can say that ever since the use of oil paint, the glazing technique started to be used. From the early masters during the 15th century till today glazing has been a well-established technique that has been used for several different reasons.
One important reason was to diminish the risk of cracking paint. Due to inferior quality of linseed oil or pigment the risk of cracking paint was higher than today. Today, the oil paint is of such high and reliable quality that the risk of cracking is almost brought down to only the unpracticed and unexperienced use.
The cracking of paint occurs out of several main reasons. One of the most common is aging. When a painting ages the canvas slackens as it ages as it cannot endure the long-term stress of stretching. Nevertheless, when enough oil has been applied to the paint, the risk of cracking is highly diminished. A more common, and often something that scares each painter, is the cracking that occurs by the lack of oil or improper use of additives or medium. In general (but be careful with my generalization) you can say that making paint thinner with anything other than oil will increase the danger of cracking.
However, why using several (sometimes more than 40 layers) thin layers instead of one or two fat layers?
By using thin transparent layers in painting, the film of paint becomes very strong and flexible. Something that has been proven very handy in transporting painting as well. Still, some paintings of the 16th century are flexible enough to be rolled up and reframed.
The flexibility of the film (the actual collection of different layers of paint) was a result of using more linseed oil with every layer that was added to the painting. With the discovery of the ‘fat over lean’ principle, which means that every new layer contains more oil than the previous layer, this ‘film’ became even stronger and more sustainable.
When using only one or two fat layers another problem, arise especially when the layer is rather thick. When linseed oil dries, it dries from the outside to the inside because of the contact with the surrounding oxygen. The more oxygen present, the faster the hardening process will proceed. When using a thick film of linseed oil, without any additives, the risk of shriveling paint will be a nasty effect. Some of the painting from the hands of Vincent van Goch encountered this problem. Due to the fact that Vincent was sometimes using very thick globs of paint, these globes dried, shriveled on the outside but stayed soft on the inside. (The result is that these paintings can’t be exhibited long due to the fact that the paint will start to ‘hang down’.)
Linseed oil, or flaxseed oil (flax oil), has gone a long way since it was introduced as a medium. So is linseed oil also very nutritious, extremely handy to keep wood healthy and protected, is it used for gilding and many other uses.
Within the art of painting, we know now three additional uses of linseed oil.
The first is the most used: cold pressed linseed oil for making oil paint.
The second is the stand oil. Linseed heated near 300 °C for a few days in the complete absence of air. It gives a thick oil that is excellent for glazing.
The third is boiled linseed oil which main character is faster drying due to the additive of a metallic dryer, which accelerates the drying process.

Another reason to use glazing is to create an optical depth within the paint layer. Due to the many transparent layers, each layer works as a single optical film with its own character. Together they will form a well-organized, due to the programming of the artist, spectrum of different layers resulting in an incredible beautiful effect of deep optical depth. However, this use of glazing needs a deep knowledge of materials and its behavior. Not only you need to be well organized in following the right steps with the fat over lean principle, as well a firm knowledge on pigments and it’s behavior is needed to get the requested results in glazing.  Also, and this is when it becomes a more tricky and complex process, when combining the main ingredient for glazing, which is stand oil, with other mediums. All mediums added to this process of glazing will have its own characteristic effect on each component. When just mixing things together creates a big risk of paint doing exactly what you, do not want it to do.

The technique of glazing.

To keep it simple I will stay with the main and classical approach of glazing.
Throughout the history of painting, and glazing in particular, many artist contributed to the development of this technique. However, most artist had their own specific approach and created their own mixtures, which were kept to themselves or only transferred to their students. Hardly any documentation has been left for the future to examine or study.
Now days, the modern mediums are made from either altered linseed oil or synthetic based in which, in most cases, an alkyd is the main ingredient.
We know, through studies of paintings made with the glazing technique during the 15th and 16th century, that the classical glazing technique has in its base a strict follow up of steps in which than many (personal) alterations are possible.


The base of this technique lies in the fat over lean principle. Now, what is this principle?
The fat over lean principle tells that each new layer of paint has to contain more oil than the previous one. In order to do this correctly you need to make sure that you ground layers are indeed as lean as possible. It is with this in mind that the actual ground layer, which in most cases is a paint that contains an already very lean pigment such as burn umber. To make it even leaner you can add some natural turpentine to it. In a classic approach you would than start with two more ground layers to create a good base for all the following layers. You have to keep in mind that each layer you put on there will absorb a part of the oil from the next layer. This actual process secures that each layer has a firm adhesion. With this in mind you can imagine what would happen if a previous layer were fatter than the next layer. The first layer would already be saturated from oil that it would not be able to absorb any oil from the next layer resulting an insecure and bad adhesion.
A good way to test this, Although I don’t recommend you start trying this with that beautiful painting you intend to purchase just to see whether the artist understood his craft or not, is to take a piece of painterly tape (the paper one) and tape it on the painting. If you than take the tape of and you horrifically take flakes of paint with it, you know that the fat over lean principle hasn’t been used correctly.
Therefore, to actual use this principle is more important than you would think.
However, unfortunately, it isn’t as easy as it sounds. If it even did sound easy…
To be able to correctly apply this principle it is of great importance that you have a basic idea of where you want to go with this painting. You wouldn’t be the first trying to follow this principle and get caught in the enthusiastic approach of using either to less or too much oil and end up with either a too dry or way to fat painting. It is therefore rather significant that you know what it is that you want to do, what your goal in result is and how to apply this principle.

But let’s continue with the classical glazing technique.
Now that we know how important the fat over lean principle is, we can understand better how this is applied within the glazing technique. As mentioned before, the glazing technique provides a marvelous deep and warm colour pallet when applied. But there is more to it. We know as to get certain colors we can get these colors by mixing them together. If we want purple, we can add red to blue and there we go. However, this sort of colour has always a little downside: it kind of loses a bit of brightness. This is even more accelerated when some titanium white is added. You will see the colour lose it’s shine.
When we, on the other hand, start using the glazing technique to reach a purple, things start to look very different. All due to the fact that each colour, because it is trapped within its own film of oil, will maintain its own brightness.
A colour, mostly nun primary colors, which is constructed by applying the glazing technique, is so much deeper, warmer and brighter than a pre mixed colour.
During the 15th till the 17th century, when glazing was becoming an established technique, it was not unusual that a whole painting consisted of colors that where constructed by applying this technique. Although time consuming it gave two major benefits to the painting; the fact that the colors where very bright and warm and, although the artist itself could not enjoy this, the preservation of the painting become so much more secure with the rich amount of oil in the painting.
However, as you now probably can imagine, this technique required a well-constructed plan of preparing and knowing your stuff. Not only concerning the fat over lean principle but as well, a good founded knowledge on each pigment, oil and other additives was required to work with this technique.
To require a result, which was determined ahead, one needed to start with a base colour. It than can take up to more than ten layers to get to the required result. Each layer added needed to be increased in oil and in transparency as to maintain all influences of all the previous colors added to this process. You can imagine that, if you would make a section of a paint film, you could see layer over layer of transparent colors that eventually, combined, produce a beautiful colour.
In some cases, and I can speak from experience here, the glazing technique can be used in such a way that you can create such deep and bright colour scales that it appears to be a kind of opal or pearl colour mix. This can be obtained by adding many different colour layers to a light colour base. The light base colour will serve as a reflector for the incoming light, which then when reflected, go back through the different layers of colors. The result is in tremendous colour range, which will be different from each angle.
The beauty of this technique is the pure fact that you can create the most beautiful and impressive colors that will, indeed, give a wonderful experience when you play a bit with light.

Now, I can understand that, while reading this article, I must confess that it still is a bit abstract; you might find that you’re still with the wonder of how you might start the glazing technique. The thing is that, although when you understand the basic fat over lean principle it becomes easier, this technique is rather complex. Each pigment has its own character, response differently to each other pigment and even to adding oil. Then there is the fact that in a lot of cases you want to add another medium such as poppy oil or safflower oil to make the substance thinner. When working with several layers of stand oil, an unavoidable effect will be that each following layer will be harder to add. Linseed oil needs a very long time to harden. In some cases more than a year. It is because of this that when you want to varnish your painting you should always wait for one year to do so.
However, during the process of glazing you cannot wait that long. In fact, it would destroy the whole process because the paint film would have been hardened too much to make it able to absorb any oil from the next layer.

However, as to not leave you empty handed after reading this article, I want to give you a very basic program, which you can use to experiment. It tells you all the steps from start to finish but without any specifics of measurements. This program does not tell you the classic, and more complex method, approach but will keep it simpler as to understand the basic principle of fat over lean.
If you have any questions just send me a mail. I’ll be happy to help.
You are also most welcome to join my classes in case you’re living in the neighborhood.


Step 01.         Grounding layers.

Make the first layer from only burnt umber with just enough turpentine to make the paint a bit thinner. Don’t drawn your canvas. Make it a smooth layer.
The next day you can put the second layer. Use burnt umber, ultramarine blue and some titanium white. (approximately 1:1:1) Do not add anything to it.
The third ground layer is the same as the second one but you might add a bit more titanium white to it. To this layer you add two drops of stand oil.

Step 02.         Setting up you painting.

To make sure that all the paint you use here has the same ratio of added stand oil is might be wise to pre-mix your paint. The amount of stand oil added to this paint must be slightly more than in the third layer of step 1 but still very little.

Step 03.         Working out your set up.

Before you start the actual glazing procedure you might want to work out you set up first.
If you feel you need to do this, again add a few drops of stand oil to you paint.

Step 04.         Starting the glazing.

Now that you have a good basic set up you can start with some glazing. Determine which part of the painting you want to work with. Which colour do you want and make sure to know which colors you need to use. On the other hand, making some mistakes isn’t so bad. It will give you a good experience.
Make sure that with each new layer, you add some stand oil to the new layer. When you want to work transparent, you can add a bit of turpentine to the mixture. Best is to find out by trying to get the right measurements in mixing.
If you want to keep working transparent, make sure that each following layer contains more stand oil and lesser turpentine.

Step 05.         Finishing the glazing process.

Eventually, when you come to the point that you made a serious amount of transparent layers, you might come to the point that you can’t add more turpentine anymore. Just because the rule of fat over lean made you get there. However, using only stand oil will make the paint rather thick to use. In this case you can use stand oil with still a little bit of turpentine and add a few drops of poppy oil or safflower oil. This will make the paint nice and thin and easier to work with. A warning though. The poppy oil or safflower oil has a slightly different composition, which in some cases makes it appear as if it doesn’t want to bind with the previous layer. To prevent this from happening you can pre-mix the mixture of stand oil, turpentine and poppy oil, before adding it to the paint.

That’s it! A very, very basic program to start your glazing process.
Be extra gentle and careful in adding oil. It is very common to go to fast with using too much oil.  For the rest, have fun! Experiment, do it with joy and without expectations. See it as a learning process. Makes it so much more enjoyable.