We know what Isaac Newton looked like. We know the shape of Euler’s face, the set of Darwin’s jaw, the intensity of Marie Curie’s gaze. We know these things because artists recorded them, using techniques that ranged from oil painting to copperplate engraving, from chalk drawing to the subtle tonal gradations of mezzotint. Every portrait of a scientist made before the mid-nineteenth century is a handmade object, the product of hours (sometimes weeks) of skilled labor by an artist working with pigments, metal plates, and printing presses.
The techniques used to create these portraits shaped how we see the scientists today. An oil painting conveys authority and permanence. An engraving allows mass reproduction and wide distribution. A mezzotint captures the soft play of light on skin and fabric with an intimacy that other printmaking techniques cannot match. Each medium imposes its own visual language on the subject, and understanding that language helps us understand both the art and the science it represents.
Oil Painting: The Original
The oil portrait was the gold standard of visual representation from the Renaissance through the nineteenth century. Oil paint, made from pigments suspended in linseed or walnut oil, allowed artists to build up layers of translucent color (glazes) that captured the subtle variations of skin tone, the sheen of silk, and the depth of shadow. No other medium could match oil painting’s range of tonal values and color richness.
Commissioning an oil portrait was expensive. Only wealthy individuals, institutions, or patrons could afford it. This is why most scientific portraits depict scientists who had achieved fame and patronage during their lifetimes. Newton was painted by Godfrey Kneller in 1689, shortly after the publication of the Principia, when Newton was already recognized as the leading natural philosopher in England. The Kneller portrait, now in the National Portrait Gallery in London, shows a sharp-featured man with penetrating dark eyes, dressed in the sober clothing of a Cambridge don. It is the image of Newton that most people carry in their minds.
Newton sat for multiple portraits during his later career as Master of the Royal Mint and President of the Royal Society. Each artist brought a different interpretation. James Thornhill painted him in 1710 as a dignified elder statesman. John Vanderbank painted him in 1725 as a wigged and composed grandee. The contrast between the youthful intensity of the 1689 Kneller and the settled authority of the later portraits traces Newton’s transformation from a reclusive Cambridge scholar to a public figure.
The process of oil portraiture required multiple sittings. The subject would pose for the artist, typically for several sessions of two to three hours each. The artist would first sketch the composition in chalk or charcoal, then block in the main areas of color, and finally refine the details over subsequent sessions. The face was always painted from life. The hands, clothing, and background might be completed from memory, from a mannequin, or by studio assistants.
Engraving: Science for Everyone
Oil paintings are unique objects. Only one person (or one institution) can own an original. To distribute an image widely, it had to be reproduced, and before photography, the primary method of reproduction was engraving.
In copperplate engraving, the image is cut into a smooth copper plate using a sharp tool called a burin. The engraver pushes the burin through the copper, removing thin curls of metal and leaving grooves (incised lines) in the surface. Ink is then applied to the plate, filling the grooves. The surface is wiped clean, leaving ink only in the grooves. Paper is pressed against the plate under heavy pressure, transferring the ink from the grooves to the paper. The result is a print in which the image is composed entirely of fine lines.
Engraving was the dominant method of reproducing portraits from the sixteenth through the eighteenth century. When a painting of a famous scientist was completed, an engraver would often be commissioned to produce a plate from which hundreds or thousands of prints could be made. These prints were sold individually, included in books, or distributed as frontispieces to scientific publications.
The engraving process imposed its own aesthetic. Because the image is built from lines, engravers developed techniques for suggesting tone and texture through the spacing, thickness, and direction of lines. Closely spaced parallel lines (hatching) create dark areas. Cross-hatching (lines crossing at angles) creates deeper shadows. Widely spaced lines suggest highlights. A skilled engraver could reproduce the tonal range of an oil painting with remarkable fidelity, though the result was always in black and white.
The most celebrated engravers were artists in their own right. Their interpretations of painted portraits sometimes became more widely known than the originals. The engraved portrait of Newton that appeared as the frontispiece to later editions of the Principia reached far more viewers than any of the oil paintings.
Mezzotint: The Velvet Art
For portraits, the most expressive printmaking technique was mezzotint, invented in the seventeenth century and perfected in England. Unlike engraving, which builds an image from lines, mezzotint works from dark to light.
The process begins with a copper plate whose entire surface has been roughened using a toothed tool called a rocker. The roughened surface holds ink uniformly, printing as solid black. The artist then smooths selected areas of the plate using a scraper and a burnisher. Smooth areas hold less ink and print as lighter tones. Completely smooth areas print as white. The result is an image with continuous tonal gradations, from deep black to pure white, without visible lines.
Mezzotint was ideally suited to portraiture because it captured the soft transitions of light and shadow on the human face. The technique was so popular in England that it became known on the Continent as la manière anglaise (the English manner). Many of the finest scientific portraits of the eighteenth century were produced as mezzotints, including several of Newton and members of the Royal Society.
The disadvantage of mezzotint was durability. The roughened surface of the plate wore down quickly under the pressure of printing, limiting the number of high-quality impressions to a few hundred. Late impressions from a mezzotint plate lost the delicate tonal gradations that made the technique so appealing. For this reason, fine early impressions of mezzotint portraits are now rare and valuable collectors’ items.
Etching and the Sketch Aesthetic
Etching offered a less formal, more spontaneous alternative to engraving. In etching, the copper plate is coated with an acid-resistant ground (a waxy substance). The artist draws into the ground with a pointed needle, exposing the copper beneath. The plate is then immersed in acid, which bites into the exposed copper, creating grooves. The depth and width of the grooves depend on the length of time the plate is left in the acid.
Because the artist draws with a needle rather than pushing a burin through metal, etching allows a freer, more spontaneous line quality. Etched lines can curve, vary in thickness, and cross each other in ways that are difficult to achieve with the burin. This made etching popular for informal portraits, caricatures, and sketches from life.
Many scientific portraits exist as etchings, particularly the more informal and intimate ones. They capture scientists at work rather than posed for posterity: reading, writing, or engaged in conversation. These images have a directness and informality that oil paintings and formal engravings lack.
Lithography: The Democratic Medium
In 1796, Aloys Senefelder invented lithography, a printing technique based on the mutual repulsion of oil and water. The artist draws on a smooth limestone surface with a greasy crayon or ink. The stone is then moistened with water (which adheres to the unmarked areas and is repelled by the greasy marks) and inked with oil-based ink (which adheres to the greasy marks and is repelled by the wet areas). Paper pressed against the stone picks up the inked image.
Lithography was faster, cheaper, and more versatile than engraving or mezzotint. It allowed artists to draw directly on the printing surface, without the intermediate step of cutting or etching metal. It could reproduce fine tonal gradations (using a technique called lithotint) and could print in color (using multiple stones, one for each color, in a process called chromolithography).
By the mid-nineteenth century, lithography had become the dominant method of reproducing images, including scientific portraits. The great portrait collections of the Victorian era, which documented the faces of scientists, engineers, artists, and statesmen, were primarily lithographic productions. The technique remained important until it was gradually replaced by photographic reproduction in the late nineteenth and early twentieth centuries.
Photography: The End of an Era
The invention of photography in the 1830s and 1840s fundamentally changed scientific portraiture. A photograph captured a likeness mechanically, without the intervention of an artist’s hand or interpretation. It was faster, cheaper, and (in a certain narrow sense) more accurate than any painting or print.
But photography also lost something. An oil portrait is an interpretation: the artist chooses what to emphasize, what to suppress, and how to compose the image. The Kneller portrait of Newton is not just a record of Newton’s face. It is a statement about Newton’s character, authority, and place in the world. The later photographs of Einstein or Bohr are documents. The earlier paintings of Newton, Euler, and Gauss are arguments.
This is why the painted and engraved portraits of scientists retain their power. They show us not just what these people looked like but how their contemporaries wanted them to be seen. A portrait of Gauss in the formal style of German academic painting says something about how Germany valued its mathematicians. A mezzotint of Newton in the English manner says something about how England honored its natural philosophers. These images are historical documents in their own right, as informative about the culture that produced them as about the scientists they depict.
The Faces Behind the Science
The tradition of scientific portraiture spans four centuries, from the oil paintings of the Renaissance to the photographs of the modern era. Each medium brought its own capabilities and limitations, its own aesthetic language, and its own relationship to the subject. Together, they form a visual archive of scientific achievement that complements the written record of papers, books, and equations.
Kronecker Wallis’s Portraying Science brings together over 400 pages of these portraits, spanning the 16th through the 19th century. The book presents scientists as their contemporaries saw them: through the eyes of the artists who painted, engraved, and printed their likenesses. It is a reminder that the history of science is not only a history of ideas. It is also a history of people, and we are fortunate that skilled artists took the time to record their faces before photography made the job easier but, in some ways, less revealing.
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