Drawing the mouth

The mouth is our most variable, expressive and animated feature. It helps us communicate how we feel both visually and verbally, as well as to eat, kiss, laugh and so on. It relates to the one moving part of the skull – the jaw – and is surrounded by a complex web of muscles that can generate an enormous range of facial expressions. In short, the mouth changes constantly from one moment to the next, and this can make it tough to draw. But to portray our subjects convincingly and emotionally, we have to know how the mouth works.

Like any other part of the body, the mouth and lips vary a great deal, depending upon sex, age, ethnicity and so on. 



Although the mouth is essentially flesh, it still relies upon the underlying bone structures. This becomes obvious in people without teeth, whose mouths sink inwards because the teeth are no longer pushing them out.

The muzzle

Firstly, let’s put the mouth in context. Beginners often draw faces flat, but there is actually a slight forward projection to the skull. This muzzle is much more pronounced in animals, for example other primates, than in humans, and we tend not to notice ours. But the denture sphere or tooth cylinder creates a curvature that artists must be aware of. As Andrew Loomis advises:

To impress upon yourself what the roundness of this area really is like, take a bite out of a piece of bread and study it. You will probably never draw lips flatly again.
(Drawing the Head and Hands)

We can see the curvature clearly in a profile of the skull. We can imagine the region as a slightly bulging oval, from the top of the chin to the nose. The lips then wrap around the volume.

George Bridgman, in his Complete Guide to Drawing from Life, conceives the two dental arches as a slice of cylinder:

Notice how the lips curve round the cylindrical volume of the muzzle – this is more obvious at an angle such as a three-quarter view. Knowing this helps us understand how the mouth sits in space: in a front view, the centre of the lips is slightly nearer to the viewer, and the sides of the mouth curve away from us.

Structure

The lips are soft and highly mobile features located between the nose and the chin. As artists we can conceive them in five sections, resembling pads – the upper lip comprises three forms and the bottom lip two. The top middle form is called the tubercle and is like a wedge in-between the other forms. On real lips you won’t always see these forms distinctly, but they are a useful starting point, especially for beginners. 

As emphasised by the contour lines, the lips are not flat. They are three-dimensional forms whose sections nestle amongst one another. They partly overlap, especially when seen at an angle, which contributes to a sense of depth. The lower lip tends to be fuller and more rounded than the upper. Notice how the low points of the lower lip are further out than the high points of the upper lip:

Of course, mouths vary a great deal from the ‘standard’ pictured here, but we can modify the five-section structure to reflect the many forms the lips can take:

There is of course no outline where the lips meet the surrounding flesh, just a meeting of colours and planes: the lips are usually redder thanks to blood vessels under the skin. Sometimes people wear lipstick or lip gloss, which add bright, artificial colours to the lips and create harder, shinier highlights.

The upper lip tends to slant downward and so falls into shadow, appearing a little darker than the lower lip, which faces upwards and therefore catches more light and highlights. In fact, in profile view you can see a series of alternating up-planes and down-planes, from the base of the nose to the chin. Assuming a front view with a typical artist’s light, i.e. from above, you get a ladder of light and dark, like this:

At either corner of the mouth there is a slight bump called a node, formed by the attachment of several muscles that pull at this area. The form here is similar to a bean, and, without over-emphasising it, you should depict it as a three-dimensional volume.

You can see that where the corner of the mouth meets the lower cheek it creates a slight depression.

Below this in the lower lip region, there are two forms angled inward on either side of the mentolabial furrow, known as the pillars of the mouth (highlighted blue below). If you take a look at bearded men, you’ll observe that facial hair tends not to grow in this area.

There is often a crease in the skin between the cheeks and the lips that can appear at any age, especially when the mouth stretches into a smile, but becomes more pronounced as we get older. Known as the nasolabial fold (or furrow), it reaches from the nostril to the corner of the mouth. The skin tends to fold there because of the pulling of muscles and the way fat is distributed in the cheeks.

Between the nose and the lips is a concave groove called the philtrum. The philtrum basically consists of two planes that dip into light/shadow, then out. The bowl of the groove is deepest in the centre.

Teeth

We briefly discussed the teeth in our post on the skull. There are sixteen teeth in either dental arch: the front teeth are for cutting and chopping, the back ones for grinding. When we open our mouths, e.g. when we smile, the upper teeth show. The lower teeth tend not to be visible except in more vigorous motion such as laughter.

As we smile or laugh, the corners of the mouth are pulled back on either side, making the top lip more straight and flat while the lower lip extends downwards and curves dramatically.



The upper six teeth roughly line up with the outside of the nostrils:

The line-like divisions between the teeth are very subtle, and can easily look like gaps if you make them too heavy.

The chin

Under the lower lip is a depression called the mentolabial furrow, below which we have the bulge of the chin. The chin is a bit like a convex bowl. From the front, the bottom of the chin adds a straight-ish line to the jaw, sometimes with a slight dent in the middle.

Chins vary as much as any other feature. They can be narrow or wide, fat or thin, bulging or pointed, square or round. Some have a dimple in the middle. 

Tips on painting the mouth

Common errors include drawing the division between the lips perfectly straight, and making the colour shift between skin and lips too dramatic. The corners inside the open mouth tend to be very dark as they are shadowy interior recesses.

The top edge of the upper lip has a narrow plane that sometimes catches light. When we know this it can be tempting to draw a white line all along the upper lip, but for realism we should treat it more subtly, maybe adding a few lights in key places.

The light on the upper lip will be affected by the rounded form of the muzzle. If the centre of the mouth is well lit, the sides will appear subtly darker as the surfaces curve slightly away from the light.

On the lower lip near the corners of the mouth there is a change of colour but no change of plane, so artists sometimes fade out the line of the mouth there.

As always, we must note that the methods listed here are only rules of thumb. Real people are highly variable, so there is no substitute for observing them in life.

Drawing the lips

To round off this post, here is a step-by-step tutorial on how to paint a realistic mouth. I’ve chosen a slightly parted mouth for my subject. When the mouth is more wide open, that is another challenge again as you need to consider the teeth, tongue etc.

1. Canvas

Create a new canvas and fill it with a neutral colour as a base. We will paint the flesh tones on extra layers on top.

2. Sketch the mouth

On a new layer, sketch the mouth. You can draw from imagination, or you may be using a reference – either a photo or a live sitter.

Start by capturing the broad shape, then mark in the upper and lower lips and their corners. Sketch out the five divisions – three in the top lip, two in the bottom lip – and mark the groove of the lower lip, the nasolabial fold and the mentolabial furrow. Be aware of the angle of the head, as the lips must agree with that angle. Perhaps indicate the nostrils too, to add some context.

3. Colour blocking

On a new layer below the sketch, block in the main regions with basic colours. My subject is white-skinned. It’s better to put the teeth on a separate layer underneath the lips. Decide upon your light source and start to indicate the main forms.

Indicate all the areas, such as the pillars of the mouth. Try to include a range of colours instead of just lighter and darker versions of the main flesh colour.

4. Shading

Build up the basic details and forms by adding some highlights and shadow areas, without overdoing the contrasts. Think about the planes when distributing your lights and darks. My light is more or less central and from above. To help you visualise your subject’s three-dimensionality, imagine contour lines running over the forms.

I’ve indicated the nose for a bit of context but won’t develop it any further. I’ve also flattened the sketch layer into the colour layer and will just paint over it from now on.

5. Work on the lips

The corners of the mouth will be darker – this is not a line but a shadow caused by the meeting of two forms. The lips have visible striations on them so don’t blend these out. Indicate the ‘bean’ shape of the nodes, and little light plane at the top of the upper lip.

The lips aren’t red cutouts stuck on the face, they emerge organically from the flesh, so look to break down any hard edges. Particularly fade out the outside edges of the bottom lip where the transition between lip and skin is more gentle. If the highlight has a hard edge the lips will look glossy, so unless they are wet, or the subject is wearing lipstick, try to break down the edge there too.

The inside of the mouth will be dark at the corners, and the upper teeth will throw the lower ones into shadow. The teeth are not necessarily one shade of white. You may see some yellow, grey or blue in there too.

6. Add details

To finish off, and without overdoing them, touch up your highlights and darks. Make sure you are happy with the amount of contrast across the whole picture and adjust your values. Look for places where a harder edge does add something: in the corners, or the teeth, or in the middle of the lips as they are a little closer to the viewer.

Add some texture on a new layer at low opacity: dabble with a speckled brush, or scribble freely with a very small normal brush. Smudge it a bit to avoid any too-obvious dots – then duplicate the layer, darken it and shift it sideways a bit to increase the sense of texture. Try to observe and paint some of the larger specks that give the skin its texture.

The mouth region has downy hairs even in people with no moustache or beard, so consider a few hairs on the top lip. Women have these hairs as well as men, except they’re finer and lighter, making them harder to see.

My finished mouth study. Click to enlarge.

Here are some studies I did: