1. Wherever two lines cross, especially at a steep angle, the illusion of a congestion appears.
  2. To combat this, type designers make some lines thinner near the joints. This is called tapering.
  3. Even the most geometric of typefaces use this trick to actually appear more geometric.

Many of you know the project Leon Sans. It is a geometric sans serif constructed using code only by designer Jongmin Kim. Apart from being a very nice geometric typeface, Leon Sans possesses some interesting features. One of them is the fact, that glyphs in the project are constructed using only a stroked line. This, especially in heavier weights, leads to a sense of heaviness around the place where two lines meet (joint). Take a look:

leon sans

Animated gif showing Leon Sans in detail. Via Behance


In type design lingo such an effect is called a congestion. When two lines meet at 90 degrees angle, the effect is usually not very pronounced, but it becomes very conspicuous when there are acute angles or multiple lines involved. Actually strokes of same weight will appear heavier, when close to one another. When looked at from a distance, text set with a typeface in which there are a lot of congestions will have ugly blotches in places where the effect is most pronounced. Historically in print this could result in actual blotches as much more ink gathered at points of line contact. That’s why they were called congestions, I suppose.

Congestions A free typeface found on the internet with a really bad case of congestions

Typical occurrences

The problem affects mostly low contrast typefaces (sans serif and slab serif) since the optical effect only appears, when two strokes are of similar thickness. Most glyphs, if designed badly, can be subject to congestions, yet there are several that prove especially problematic. Due to complicated construction I would point out /a and /g (the two stories versions), /k, /x, /B, /8, /& or /$. Due to presence of acute angles congestions appear in /A, /V, /W, /4, /N, /n, /p, /b, /q and so on.

Typical occurences Several glyphs where congestions often appear


Type designers, faced with this problem at the birth of sans serif, have developed several clever tricks to rid their products of such annoyance. The most common solution for congestions is to make one (or both) of the connecting strokes thinner at the joint. This is called tapering, and almost every typeface, even the most geometric ones, utilise this trick. In the image below you can see how Paul Renner did this with Futura.

Futura /n /n’s arch is thinner where it meets the stem. Both arms of /v get thinner towards the joint.

Another method can be used in such glyphs as /n, /h, /u and so on. In this case we are presented with a construction consisting of a vertical stem and a shoulder branching away from it. The trick here is to make the notches between the shoulder and the stem bigger. It can be achieved by slicing a part of the stem off or by pointing it away. In my latest project I have decided on the first approach.

Phrasa The top part of the /n’s stem has a slight notch, relieving the point of congestion.


Only very sporadically type designers decide to forego these techniques. Those that do tend to fall into two categories:

  1. They lived in 1920s, and were avant-garde experimenters
  2. They live now, and haven’t heard about it.

Of the two, the experimenters are by far more helpful. Since they tried to do design without help of true and tested methods from the past, we, after seeing their failed attempts, can safely assume this isn’t worth the effort.

Case in point: Paul Renner in his original drawings for Futura attempted to achieve a truly geometric design. That meant no optical corrections, tapering included. What never ceases to astonish me is how bad it looked before it started looking so good. Gives hope.

Original Futura

This shows that the existence of congestions is yet another optical effect that makes truly geometric typefaces impossible: you can’t have perfect circles, if you have to add tapering whenever lines meet

Why this matters

The subject might seem trivial to a layman, but considering how much time and careful thought of countless type designers goes into counteracting congestions in their typefaces, it is nothing but. All of it to make reading easier and more pleasant. Relieving the points of congestion can really make the difference between bad and good design. It is amazing, when you think about it, that to make a low contrast typeface work, you actually have to smuggle some contrast in. Otherwise you will end up with ugly bloating at the joints. Unfortunately I don’t really see designers from outside the typography field taking notice of this effect. If you know of any, please let me know.


Remember Leon Sans typeface from the beginning of this article? At the final stage of the design process, Jongmin Kim used type design software to create an actual font file. But while at it, he also added tapering to the design. You can watch him do it here.

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