5 Key Elements to Illustrating "Glass"

Updated: Oct 20, 2020

Here in the Practice Corner we specialize in techniques not projects. How do we do that? In the process of developing our skills, Kathy and I have learned that spend time digging deep into the technique until we understand what it’s all about helps us identify the key elements of the technique. Then we practice these elements to improve our skill, which also boosts our confidence for tackling future projects. It is this process where the Practice Corner was born.

June, in the Practice Corner, is all about illustrating glass.

Kathy and I are not teachers, but we have a ton of hours practicing techniques under our belts.

We love to share our experience with members in the Practice Corner as we help them along their artistic journey. So when we want to improve on a technique we still take classes and do research on what can help us build our skills. So let me share with you a few things we have learned that are key components of illustrating realistic glass.

Before we get into that, I think it is critical to talk about light and how it works with glass. I recently spent time researching how light interacts with glass. There is no secret, or anything surprising here, but when you color glass it is important to know what is happening with the light so you can illustrate it realistically. Light does three things to glass: 1, light transmits through glass, 2) some of the light is absorbed, and 3) some of the light is reflected back at the viewer.

This is why when you look at glass from one angle it looks different from that of another angle because of how the light is interacting with the glass from your current perspective.

Now that I’ve shared with you the importance of light, let's explore some of the components of glass that matter when we want to illustrate glass with realism.

Hard Highlights

When the light is reflected directly back of glass it creates what we see as a very hard highlight. Usually when we color highlights on non-glass objects the highlight is not pure white because the highlights reflect (include) part of the object color back. With glass, there are spots where the light hitting the glass is not absorbed and it bounces off the surface of the glass. When we color we can create this hard highlight by using the white of the paper. There are additional techniques that we can employ to brighten the hard highlight if the paper color itself isn’t enough. Such as, but not limited to darkening everything around the hard highlight or using white pens (i.e., white gel pen or white paint pen) or other mediums that can achieve this hard bright highlight.

Soft Highlights

When the light is reflected back but the angle of the reflection is not directly back to the eye so it looks softer or more diffused. You can observe soft highlights in photos of glass objects by looking for the hard highlight, normally opposite of this hard highlight you will see the soft highlight caused by the light that has transmitted through the glass and is exiting through the glass on the other side. You can create this when you color by fading the white off of the hard highlight or using an off white transparent medium, or simply applying a lighter application of your soft highlight color.

Glass Thickness

Interestingly enough, if you stare at a glass long enough you will start to see how the light changes at different angles as the light tries to go through the thickest part of the glass. As an example, at the base of every glass drinking glass you will see the thickness of the glass increase and you will see the light act differently based on the thickness. The tonal values change as the glass thickness increases. In some areas you will not see through the glass as the light has been completely absorbed by the glass. To our eye it looks like a black spot. This is where coloring based on value is key in creating the realism you are looking for. It is key to observe your reference very closely to see the change in values in this area - meaning where does it get darker and where does it get lighter and the gradual steps in-between.


As we know about how light interacts with the glass but you also have to remember how glass reflects its surroundings. A clear glass vase with roses in it sitting next to a green bowl of cherries will pick up not only the colors of the the bowl, cherries, but also the green stems of the roses will reflect off the glass of the vase. Of course how much color is reflected and how well you can see the shapes of the surroundings is based on the angle and intensity of the light. The good thing about being creative, you do not need to know the science behind the reflections and calculate the right angles all you need to do is observe your reference and notice the details that will add life to your coloring.


There are a couple of things about distortion I want to share. When there is something inside of the glass, like water or my favorite wine, it will look a bit distorted. Do you remember being a kid and sticking your finger in your glass of water just to see how big it made your finger and you thought water was magic liquid. Well it wasn't really the water making our fingers look funny, it was the light that created this distortion. This is because light waves slow down and bend when they hit glass. When creating distortion you must pay close attention to your reference and color what you see not what you think you see. When you look at the glass as a whole the distortion reads to your eye as this is a realistic glass but often times when looking close up at the distortion things seem to be off and your brain will want to correct the weird things you see. Remember that what you are coloring appears distorted, but it is realistic and therefore we need to capture it when we want to create realism in a glass illustration.

These elements are just a few key components to illustrating stunning glass. There are so many more avenues to explore about glass objects.

If you want to learn more about illustrating glass and how to practice these elements to create beautiful glass come hang out with us in the Practice Corner for the month of June as we guide you though practicing this technique.

If you are reading this after June, don’t despair, you can still explore and practice creating glass with realism by purchasing the "Glass" Technique Practice Pack here!

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