When it comes to faxing, there are some better fonts than others.
Fonts designed for fax
Fonts designed for low resolution visibility are optimal. The Lucidia family of fonts is specifically designed for low resolution and small font sizes. It even has a font “Lucidia fax” which was designed for transmission over low resolutions environments such as fax.
It is available with Microsoft Office.
Other good fonts
Low resolution and small font legibility is the most important factor for font quality in a fax.
Serif or Sans-Serif?
There are different opinions on this. Fonts such as Lucidia Fax are a Serif font, however, fonts recommended for limited visibility are typically Sans-Serif.
Avoid fonts that are too thin
Fonts that have very thin lines are more likely to have trouble in a fax transmission.
As a letter’s line may be only one or two pixels thick, small lines are more likely to have noticeable errors from a fax transmission.
Contrast matters – don’t use colors or grayscale fonts
Any use of color (especially yellows, oranges, and lighter colors) will make a grey image in a fax, which will be harder to read once it is received.
Some fonts have a grayscale effect where they are not completely black, avoid those as well.
Don’t invert colors or use all black backgrounds
Sending an all-black page with white writing will have lots of contrast, but will be very hard to read. The small errors in a fax transmission will be very noticeable when the fax arrives.
Also, you’ll risk black faxing the person you’re sending the fax to, emptying their fax machine of toner. The transmission time would be very long with an all black fax as well.
Avoid fancy fonts and script fonts
The fancier the font, the more it should be avoided.
With the exception of logos or cover page art (at a large font size), fancy fonts should be avoided in a fax.
The worst fonts for sending on a fax are either greatly embellished or emulate a script (handwriting).
Some examples of very bad fonts to fax with:
Research on font legibility
A list of typefaces for dyslexia appears to have similar font requirements as low resolution environments, including popular fonts Ariel, Verdana, Trebuchet, and Calibri.
The American Foundation for the Blind recommends printing with standard Roman or Sans Serif fonts. Ariel is recommended.
The Canadian National Institute for the Blind’s print recommendations are Ariel and Verdana.
Font size and layout matter, too
A larger typeface will be clearer when sending through fax. 9pt font is the bare minimum for fax, 14-16pt would be ideal.
Layout that doesn’t have images and diagrams crowded very close to text will be easier to read when they are sent through a fax.
Improving transmission quality of fonts in a fax
When sending a fax, the best way to improve transmission quality is to directly send the fax electronically (using an online fax service or computer fax) instead of printing it and then faxing it.
Just like photocopying a document results in a small loss of quality, printing and faxing a document (which involves scanning it) creates a slightly lower resolution document than directly sending it electronically.