Old mathbook's thick font

Question

I did a lot of research to re-create the style of the following math book written in 1979:

There are many questions around recreating old fonts such as font-of-old-math-books , how-to-write-like-old-mathematical-papers , old-books-appearance-and-font and I found that the closest would be the Old Standard font in XeLatex.

I noticed, that the older fonts are always a big bolder than the Latex fonts, including Old Standart.

Does anybody know a more suitable, thicker font or a way to thicken (increase the weight of) the font for the whole Latex document? And can you identify the math font (and make it thicker as well?

There are some solutions to the last questions in 1, 2, 3 but I did not find a solution how to scale it globally.

Answer 1

Fonts in the computer modern family are very light by design, so most other font choices are bolder, but here I have forced the Times-like TeX Gyre Termes and Stix Two Math fonts to be adjusted to be bolder (but less bold than the designed bold font)

Credit to mathpix for ocr your image to error free LaTeX

\documentclass{article}

\usepackage{unicode-math}
\setmainfont{TeX Gyre Termes}[FakeBold=1]
\setmathfont{Stix Two Math}[FakeBold=1]

\begin{document}

\textbf{Example}

In particular, if $X_A\left(t, t_0\right), X_A\left(t_\theta, t_0\right)=I, X_B\left(t, t_0\right), X_B\left(t_0, t_0\right)=I$, are fundamental matrix solutions of $\dot{x}=A(t) x, \dot{y}=B(t) y$, respectively, then
\[
\begin{aligned}
\left|X_A\left(t, t_0\right)-X_B\left(t, t_0\right)\right| \leqq & \sup _{t_0 \leqq u \leq t}\left|X_B\left(u, t_0\right)\right|\left(\exp \int_{t_0}^t|A(s)| d s\right) \\
& \times \int_{t_0}^t|A(s)-B(s)| d s
\end{aligned}
\]
for all $t \geqq t_0$. Relation (1.11) implies that the principal matrix solution of $\dot{x}=A x$ is a continuous function of the integrable matrix functions $A$ defined on $[0, t]$ with $|A|=\int_0^t|A(s)| d s$.

When a linear differential equation contains general time varying
coefficients, the remarks in this section essentially comprise the
theory concerning the specific structure of the solutions. For special
equations, much more detailed information is available. For equations
with constant or periodic coefficients, the general structure of the
solutions is known and discussed in Sections 4 and 7.
\end{document}

For xelatex you may need to reference the fonts by filename so

\setmainfont{texgyretermes-regular.otf}[FakeBold=1]
\setmathfont{STIXTwoMath-Regular.otf}[FakeBold=1]

Answer 2

Another option may be is to use pdfrender

You can control the boldness/thickness and many other options as described in the documentation of the package.

\documentclass{article}

\usepackage{amsmath}
\usepackage{amssymb}
\usepackage{xcolor}
\usepackage{pdfrender}
\pdfrender{TextRenderingMode=2,LineWidth=.5pt}

\begin{document}

\textbf{Example}

In particular, if $X_A\left(t, t_0\right), X_A\left(t_\theta, t_0\right)=I, X_B\left(t, t_0\right), X_B\left(t_0, t_0\right)=I$, are fundamental matrix solutions of $\dot{x}=A(t) x, \dot{y}=B(t) y$, respectively, then
\[
\begin{aligned}
\left|X_A\left(t, t_0\right)-X_B\left(t, t_0\right)\right| \leqq & \sup _{t_0 \leqq u \leq t}\left|X_B\left(u, t_0\right)\right|\left(\exp \int_{t_0}^t|A(s)| d s\right) \\
& \times \int_{t_0}^t|A(s)-B(s)| d s
\end{aligned}
\]
for all $t \geqq t_0$. Relation (1.11) implies that the principal matrix solution of $\dot{x}=A x$ is a continuous function of the integrable matrix functions $A$ defined on $[0, t]$ with $|A|=\int_0^t|A(s)| d s$.

When a linear differential equation contains general time varying
coefficients, the remarks in this section essentially comprise the
theory concerning the specific structure of the solutions. For special
equations, much more detailed information is available. For equations
with constant or periodic coefficients, the general structure of the
solutions is known and discussed in Sections 4 and 7.
\end{document}

Compiled with lualatex on TL 2022.