Rigden method

The Rigden method is a laboratory technique for measuring the specific surface area of fine powders by determining how easily air flows through a packed bed of the material. In asbestos science, it has been used as a quick way to estimate the fineness of fibrous and dust samples, since longer or thinner fibers produce more surface area per gram. It is an indirect, bulk measurement rather than a fiber-by-fiber analysis.

Origin

The technique is named after P.J. Rigden, a British researcher who in the 1940s refined air-permeability methods (building on earlier work by Lea, Nurse, and Carman) for measuring the surface area of cement and mineral powders. It became a standard industrial particle-sizing tool before modern electron microscopy was widely available.

Significance in Asbestos Context

Historical industrial-hygiene and product-testing records sometimes report fiber fineness using Rigden or related permeability values rather than fiber counts. If your exposure history involves older mining, milling, or manufacturing operations, internal company records may use this kind of bulk surface-area data to describe the dustiness or grade of the asbestos handled. Modern experts generally rely on transmission electron microscopy (TEM) or phase-contrast microscopy (PCM) for fiber characterization, but Rigden-era data can still appear in archived industry documents and may help establish what companies knew about the fineness, and therefore the respirability, of their product.

Example Sentence

The plaintiff's expert pointed to mid-century quality-control logs that used the Rigden method to grade fiber fineness, arguing the company tracked, and understood, how respirable its product was decades before warnings appeared.

Related Terms

Specific Surface Area, Phase-Contrast Microscopy, Transmission Electron Microscopy, Respirable Fiber, Fiber Burden Analysis, Industrial Hygiene

Notes

• If your case involves older asbestos mining, milling, or textile work, ask your legal team whether internal grading or quality-control records (including Rigden or permeability data) have been subpoenaed from the manufacturer.
• Do not rely on Rigden-style measurements alone to characterize your exposure. Modern fiber counts and electron microscopy are the accepted standards; this method is mainly useful as historical corporate evidence.
• Preserve any old employer documents, product datasheets, or grading certificates you may have, even if the terminology looks unfamiliar; they can be meaningful to an expert reviewing your exposure history.