1902 — 85% Magnesia
A 1975 company listing places 85% Magnesia block and pipe covering at the beginning of the twentieth century, with a listed discontinuation year of 1970.
Johns-Manville historical product research
Johns-Manville Insulation Product Timeline
Follow the names and dates of historical pipe covering, blocks and insulation materials—from magnesia and Superex to Thermobestos and later replacement names.
A product-name timeline
1902–1903 — Asbestocel and Anti-Sweat
The company listing dates Asbestocel (aircell) pipe products to 1902 and Anti-Sweat pipe products to 1903; both are listed as discontinued in 1965.
1922 — Superex 1900
Listed in both block and pipe forms. A later company response identifies Superex 2000 as a replacement name around 1971–1973.
1930 — Superex-M
Listed as block and pipe covering; the later response names Superex-1600 as a replacement around 1971–1973.
1939 — Thermobestos
Listed in block and pipe forms. Later company materials identify Thermo-12 as a replacement around 1972–1974.
1958–1959 — MIN-K
Company product listings include MIN-K 500, MIN-K 1301 and MIN-K 2000, and record changes in the 1970s.
1959 — Metal-On
Listed among pipe products, with later records describing a change from Metal-On (Thermobestos) to Metal-On (Thermo-12).
1966 — Silicated Thermobestos
The product listing gives 1966 as the introduction date for this named pipe product.
Why replacement names matter
A person may remember a name from a purchase order, maintenance manual or later renovation even when the original insulation was installed decades earlier. The company records show changes in product names and formulations over time. Those transitions can help narrow the period of a job or renovation.
Workplace memory prompts
What was insulated?
Boiler shells, steam mains, condensate lines, valves, pumps, vessels or engine-room piping.
What did the material look like?
Half-round molded sections, rigid blocks, felted coverings, bags of insulating cement or outer jackets.
When was the work?
New installation, plant expansion, annual shutdown, refit, replacement or demolition.
Who was present?
Insulators, pipefitters, boilermakers, maintenance crews, shipyard workers or subcontractors.
Historical records
Read the historical source: 1975 product list with manufacture and discontinuation dates ↗
Read the historical source: company response describing replacement products ↗
Continue exploring Johns-Manville history
Historical product library → Company history and Manville Trust → Start with what you remember →