Carborundum Printing (Opus Graphic): Dox Thrash (c. 1937)
The innovation by Dox Thrash of Philadelphia, Pennsylvania, describes the Carborundum Printing Process (also known as the “Opus Graphic” or “Thrash Method”). Developed around 1937 at the Philadelphia Fine Print Workshop of the Federal Art Project (WPA), this invention is a revolutionary printmaking technique that adapted industrial abrasives to create a new form of intaglio engraving. By utilizing carborundum (silicon carbide) to “pit” a metal plate, Thrash enabled artists to achieve deep, velvety blacks and a range of tonal gradations previously impossible with standard etching tools.
The “Why”
During the Great Depression, traditional printmaking—such as mezzotint—was incredibly labor-intensive and required expensive, specialized tools (like “rockers”) to prepare a plate. The primary “pain point” for Thrash and his colleagues was the mechanical barrier to tonal expression. Artists wanted the rich, dark textures of mezzotint but needed a faster, more accessible industrial method. Thrash looked to the very abrasives used to grind down lithograph stones and realized they could be used to “roughen” copper and zinc plates for engraving.
Inventor Section: Dox Thrash
Dox Thrash was a preeminent African American printmaker and draftsman whose engineering philosophy was defined by industrial adaptation. A veteran of World War I, Thrash’s experience with labor and grit influenced his artistic technicality. Working within the government-funded WPA, he bypassed the elitist gatekeeping of fine art tools by repurposing commercial abrasives. His work is a landmark in Black ingenuity, proving that the tools of the “working class” (industrial grit) could redefine the highest levels of “fine art.”
Key Systems Section
1. The Carborundum Surface Abrasion
Instead of using a sharp burin to cut lines, Thrash applied carborundum grit (silicon carbide) to the surface of a copper or zinc plate.
- Modern Term: Surface Pitting / Micro-Texture Etching.
- By rubbing the plate with another plate or a heavy muller and the grit, the surface becomes uniformly roughened with millions of tiny “wells” that hold ink.
2. The Subtractive “Burnishing” Logic
Once the plate is fully blackened (roughened) with carborundum, the artist works in reverse.
- Modern Term: Subtractive Tonal Modeling.
- Using a burnisher or a scraper, the artist smooths down the “pits.” The smoother the area, the less ink it holds, creating highlights. This allowed Thrash to “paint with light” out of a dark background.
3. The Viscosity-Ink Retention System
The unique “tooth” created by the carborundum grit allowed for a higher volume of ink retention compared to standard acid etching.
- Modern Term: High-Capacity Capillary Retention.
- This system produced the “sooty,” atmospheric depth that became the hallmark of Thrash’s images of Black life in the American South and industrial North.
4. The Pressure-Transfer (Intaglio) Press
The prepared plate is inked, wiped, and run through a high-pressure rolling press.
- Modern Term: Mechanical Compression Transfer.
- The dampened paper is forced into the micro-pits, lifting the ink out to create a three-dimensional, textured print surface.
Comparison Table
| Feature | Standard Mezzotint (Pre-1937) | Thrash’s Carborundum Process |
| Tooling | Manual “Rocker” (Slow, repetitive). | Carborundum Grit (Fast, industrial). |
| Texture | Uniform, cross-hatched burr. | Organic, granular “pitted” surface. |
| Labor | Weeks to prepare a single plate. | Hours to prepare a plate. |
| Tonal Range | Sharp transitions. | Soft, smoky, “painterly” gradations. |
Significance Section
- Democratization of Art: By using industrial materials, Thrash made high-quality tonal printmaking accessible to WPA artists who lacked expensive European tools.
- Precursor to Modern “Carborundum Etching”: The process is still taught in fine art universities today, essentially unchanged from Thrash’s 1937 experiments.
- Industrial Synergy: Thrash’s method is one of the first successful “cross-overs” where industrial abrasives (Silicon Carbide) were codified into a formal artistic medium.
- Cultural Documentation: The “velvety darkness” of the process allowed Thrash to capture the nuances of Black skin tones and the shadows of urban poverty with a dignity and depth that line-etching could not convey.
