Optimising Braille Character Spacing for Enhanced Tactile Reading
Through research and collaboration with international organisations, Zed Braille emerges as a finely tuned typeface, bridging diverse user needs and international standards.
Each version of the Zed fonts also includes characters in Braille, a tactile writing system arranged in cells and used by people who are blind or have low vision. Braille is used in different languages and scripts to represent letters, numbers, punctuation and even symbols. International standard bodies recommend the size, diameter, height and spacing of Braille characters to harmonise legibility. The formal standards were developed in the early 20th century, and the most commonly used dot diameter at present is around 1.50 mm, with an embossed dot height of around 0.50 mm, while the distance between dots (centre to centre) in the same cell is 2.50 mm, although there are some variations in these sizes.
Typotheque has conducted an extensive review of these recommendations and of the research literature in order to understand the standard in different regions across time. We realised disagreement exists on the standard dimensions of each character. For example, National Organization of Spanish Blind persons (ONCE), recommends nothing below 2.5 mm between dots, while the Braille Authority of North America currently recommends 2.3 to 2.5 mm.
Additionally, our research showed reading acuity varies widely from user to user. A young blind person, for example, will likely have a higher capacity to read smaller characters than an older patient with diabetes, who might be experiencing a loss of sensitivity in their fingertips.
To cater for all, we need to take such aspects into consideration and present a wide enough range of spacings for Braille characters.
In their 2007 study on the tactile legibility of Braille characters, authors Tetsuya Watanabe and Susumu Oouchi experimented with spacing of dots 1.05–1.15 times the standard, which resulted in shorter reading times and higher legibility scores. Their study was performed using stereocopying, a tactile printing technique that uses heat to expand the capsule paper. Stereocopying is less legible due to a swelling of the dots, compared to the more precise impact embossing, but other literature had also shown an improvement when slightly enlarging the spacing on other mediums.
We decided to replicate Watanabe and Oouchi’s research with UV ink, used for restaurant menus and paper maps, and high-precision 3D printing, oftentimes used for Braille in wayfinding. We produced several samples of the font with increased spacing in both mediums, from 2.5 mm up to 3.0 mm between dots.
Unlike printed text, Braille characters that are too large are simply impossible to read. If the dots are too far apart, each letter risks being confused with another. In addition, the user’s fingertips must fully cover not only the current character, but also reach adjacent ones. Similar to visual reading, Braille readers need to perceive each character in context. For this reason, there's an upper limit to the optimal spacing between dots.
Identifying the optimal range of spacings between Braille dots
ONCE agreed to help and assess us in this query. Marina Rojas, head of the Spanish Braille Commission and a Braille user herself, and Francisco Javier Baeza, specialist on the topic, kindly accepted our request and guided us through the process of designing Zed Braille.
At the time of writing, ONCE was preparing a new set of guidelines to update the Spanish standard, based on their recent internal research. The results were just published, and we were fortunate that our research coincided with their re-evaluation. Marina and Javier reviewed the samples inspired by Watanabe and Oouchi's research. They strongly recommended nothing bigger than a 2.75 mm distance between centres of adjacent dots. This has been reflected in Zed Braille’s design.
The typeface, designed to be set in 30 pt, allows the user to move from the most widespread standard (2.5 mm) to a 10% increase above of it (2.75 mm).
A second validation
We decided to replicate our test performing a blind experiment with an independent group. We replicated the interviews in Croatia using the exact same samples, at the County Blind Association of Split. Although the users interviewed were unaware of the other experiment, they repeated the findings produced in Spain, further confirming the optimal sizes between dots.
Our research has led to Zed Braille, a companion of Zed that expands the reach of our type system beyond visual capacity.
The design of the typeface has been carefully crafted with international regulations and recommendations in mind, allowing for the differences in spacing that we found across populations. Zed Display follows the standards and uses the dot spacing of 2.5 mm, while Zed Text is spaced more loosely, with 2.75 mm gaps between the dots. In addition, Text and Display each comes in three versions, one for embossing and two for sighted Braille users, employing unpunched dots and including outline and small-size dots.
We would like to thank Marina Rojas and Francisco Javier Baeza, from the National Organization of Spanish Blind persons (ONCE); the Blind Association of Split, Croatia; and Nikola Mikulić and Igor Čaljkušić, who kindly helped support our Croatian research. Lastly, thanks to Vectorealism in Milano and Estudi Roig in Barcelona for producing the Braille samples used in this research.