85% Magnesia

85% Magnesia is a high-temperature thermal insulation material made of about 85% basic magnesium carbonate and 15% asbestos fiber, used widely on steam pipes, boilers, and industrial equipment from roughly 1900 to the 1970s. It was sold as preformed blocks, pipe coverings, and a mixable cement, and was highly friable, releasing asbestos dust when cut or removed.

Origin

The product was developed in the late 1800s, with Philip Carey, Johns-Manville, Keasbey & Mattison, and Eagle-Picher among the major manufacturers. The "85%" designation refers to the magnesium carbonate content; the remaining 15% asbestos was added because magnesia alone is too brittle to hold shape under heat and vibration.

Significance in Asbestos Context

85% Magnesia is one of the most frequently identified exposure sources in mesothelioma and asbestosis cases involving power plants, refineries, ships, paper mills, and industrial steam systems. Because it was friable (meaning it crumbled easily when cut, sawed, or removed), insulators, pipefitters, boilermakers, Navy veterans, and bystanders working nearby inhaled high concentrations of chrysotile (and sometimes amphibole contaminants) during installation, repair, and tear-out. Identifying 85% Magnesia in a work history is often a strong link to a specific manufacturer's product line, which matters because each manufacturer is a separate potential defendant. Product identification witnesses, purchase records, and surviving block fragments analyzed by polarized light microscopy can all confirm exposure to this material.

Example Sentence

The industrial hygienist's report noted that the patient spent years removing 85% Magnesia pipe covering from steam lines at the shipyard, releasing visible dust without any respiratory protection.

Related Terms

Chrysotile, Pipe Covering, Friable Asbestos, Calcium Silicate Insulation, Thermal System Insulation, Product Identification

Notes

• Try to recall and write down the brand names of insulation seen on the job. Careytemp, Thermobestos, 85% Magnesia, and similar names point to specific manufacturers and defendants.
• If old insulation debris, packaging, or shipping records still exist at a former worksite or in personal toolboxes, preserve them; fragments can be tested by accredited labs to confirm fiber type.
• Ask co-workers who shared the same job sites whether they remember the insulation brand, color, or supplier. Co-worker testimony is often decisive for product identification.
• Navy veterans should request their service records and ship's equipment manuals, which frequently list insulation contractors and product specifications for boilers and steam plants.