Accessible Math in STEM Titles: Why Equations Should Never Be Images

A chemistry student opens her textbook on a screen reader and reaches the page on reaction rates. The paragraph reads clearly. Then the equation arrives, and the reader announces "graphic", or nothing at all. The most important line on the page has gone silent.

This happens whenever equations are set as pictures, and it is still common in STEM publishing. An image of an equation looks right in print and on screen, so nobody flags it during production. For a reader who is blind, has low vision or has a reading disability, it is a wall.

Why images fail

A picture of an equation has no structure. It cannot be read aloud, so a screen reader has nothing to speak. It cannot be enlarged without blurring, which matters to readers with low vision who magnify text. It cannot be searched or copied, and a braille display has nothing to translate.

MathML solves this by describing the equation as it is built. A fraction is marked as a fraction, a power as a power, a root as a root. A screen reader can then speak "x squared plus three x over two" in a way that follows the logic of the expression, and a braille display can render it in a maths braille code such as Nemeth. Many browsers and reading systems can display MathML as sharp, scalable text, and EPUB 3 treats it as part of the standard. WCAG 2.x asks that information carried by non-text content be available in text form (success criterion 1.1.1), and EPUB Accessibility 1.1 builds on that. Equations as images meet neither test unless someone writes out a full description, equation by equation, which is slower and less reliable than doing it properly once.

Where it goes wrong

Moving to MathML is not the end of the problem. Four failures turn up again and again.

Equations are exported as images because the typesetting tool left them that way, and nobody notices after conversion. A quick scan of the image folder in the package often finds them.

Chemical formulas and small expressions are typed as plain text or Unicode characters, so that "H2O" has a plain 2 where a subscript belongs. It looks fine and reads poorly.

MathML is present but built to look right, not to mean something. Spaces and nested tables hold the equation in shape on screen, and a screen reader speaks the pieces in the wrong order, or one symbol at a time.

The reading system does not support MathML at all. Support varies across devices and apps, so a file that works in one environment can fail in another. A text fallback in the markup, such as an alttext attribute on the equation, gives those readers something to hear.

PDFs carry the same risk in another form. An equation in a tagged PDF needs a Formula tag with alternate text, or the reader meets a gap where the formula sits.

What publishers can do

Fix the source, not the output. If authors write in LaTeX or Word's equation editor, a conversion that preserves structure produces clean MathML without retyping anything. Fixing it after release costs more than getting it right at conversion.

Then test a single chapter before releasing a list. Open the EPUB in a reading system that supports MathML. Search for a variable from an equation. Enlarge the text to 200 percent and watch for blurred symbols. Then play the chapter through a screen reader and listen to three equations: a fraction, a power and a root. If you cannot follow the maths by ear, a student will not either.

Automated checkers will confirm that MathML is present. They will not tell you whether it reads correctly. That takes a person who understands the maths.

S4Carlisle converts equations to structured MathML as part of EPUB and PDF production, and our STEM reviewers check how they read as well as how they look. With Benetech GCA certification and more than 50 years in publishing, our team knows how to keep a textbook's equations intact across every format. To test a sample STEM chapter with our team, visit s4carlisle.com or write to sales@s4carlisle.com.