The Eraser on Your Desk Is Slowly Becoming the Dust Under It

Pick up a pencil eraser and press it to paper. Friction pulls graphite into the rubber, and the rubber crumbles away carrying the graphite with it. What’s left on your desk is a receipt for every mark you decided to remove.

Edward Nairne, an English optician, discovered that natural rubber could erase pencil marks in 1770; Joseph Priestley gave the material its name that same year [1]. Early rubber erasers were fragile — they perished in heat and crumbled at room temperature. Charles Goodyear’s vulcanization process, discovered in 1839, changed that. Treating rubber with sulfur made erasers durable enough to sell [2]. Most modern erasers aren’t rubber at all. They’re PVC, and a 1997 conservation study found that the common Magic Rub eraser is roughly 34% di-n-octyl phthalate by weight [3]. Phthalates make the eraser soft. They’re also one of the most commonly detected chemical classes in household dust, shed from vinyl flooring, shower curtains, and electronics [4]. The eraser on your desk is slowly becoming the dust under it, one crumb at a time.

Shoelaces work the same way, just without the crumbs. A 2017 UC Berkeley study found that knots fail when repeated foot impacts loosen the structure and the swinging motion of the laces pulls it apart [5]. Ian Fieggen, who has run Ian’s Shoelace Site since 2000, had already explained the mechanism: granny knots sit crooked and pull themselves loose under tension, while balanced knots sit flat and self-tighten [6]. Every step degrades a granny knot slightly. The loosening is a record of distance walked.

Dust operates at the scale of a room. A 2025 University of Miami study called DIRT measured dust on the hands of 101 children and found that 90% of particles were smaller than 35 micrometers — four times below the EPA’s 150-micrometer threshold for exposure assessment [7]. Smaller particles carry more concentrated toxic chemicals and reach deeper into lungs. Current guidelines probably underestimate the risk. At Washington University in St. Louis, Jenna Ditto received a $453,000 NSF grant in 2024 to study how dust stores semi-volatile organic compounds from vehicle exhaust, cooking, and biomass burning, releasing them back into indoor air over time [8]. Everything that happens in a room eventually settles.

Erasers shrink to nothing. Knots come undone halfway down the block. Dust reappears a week after you wiped the shelf. Every one of these objects produces debris proportional to its use, and there’s no version that doesn’t. A pencil that’s never been used needs no eraser. A shoe that’s never been worn has no knot to fail. An empty room collects no dust. We keep wiping, retying, replacing, and calling that maintenance. We’re really just clearing away the evidence that something worked.

References

[1] “Eraser,” Encyclopaedia Britannica — https://www.britannica.com/technology/eraser

[2] “Charles Goodyear,” Encyclopaedia Britannica — https://www.britannica.com/biography/Charles-Goodyear

[3] Brenda M. Bernier, “A Study of Poly(vinyl chloride) Erasers Used in the Surface Cleaning of Photographs,” Topics in Photographic Preservation, Vol. 7 (1997) — https://resources.culturalheritage.org/pmgtopics/1997-volume-seven/07_02_Bernier.html

[4] “Study Finds Vinyl Plasticizers a Major Contaminant in Household Dust,” Habitable — https://habitablefuture.org/resources/study-finds-vinyl-plasticizers-a-major-contaminant-in-household-dust/

[5] C. A. Daily-Diamond, C. E. Gregg, O. M. O’Reilly, “The roles of impact and inertia in the failure of a shoelace knot,” Proc. R. Soc. A, 473:20160770 (2017) — https://doi.org/10.1098/rspa.2016.0770

[6] Ian Fieggen, “The Granny Knot,” Ian’s Shoelace Site — https://www.fieggen.com/shoelace/grannyknot.htm

[7] C. Fayad-Martinez et al., “Mass and particle size distribution of household dust on children’s hands,” Journal of Exposure Science and Environmental Epidemiology (2025) — https://pubmed.ncbi.nlm.nih.gov/39930017/

[8] “Role of dust on indoor environmental air quality gets closer look,” Washington University in St. Louis (2024) — https://source.washu.edu/2024/04/role-of-dust-on-indoor-environmental-air-quality-gets-closer-look/