Prasco (Fibreboard)

Prasco was a high-temperature insulation of diatomaceous earth and asbestos, made as blocks, pipe covering and cement.^1,2 Its makers changed names over the years before it appeared under Fibreboard.^3,4,5 A 1924 ad in Asbestos, the industry's trade journal, says Prasco blocks were made by Plant Rubber and Asbestos Works of San Francisco, which had its mill in Redwood City, California.³ In 1948 the company, by then a division of The Paraffine Companies, announced that it had become The Paraffine Companies' Insulation Division as of July 1, and that Prasco High Temperature Insulation would go on being made under that name.⁴ A 1951 Navy list of approved products names Pabco Products, Inc. of San Francisco as its maker, at a plant in Redwood City.⁶ From 1957 to 1961 it appears in ads of the Pabco Industrial Insulations Division of Fibreboard Paper Products Corporation.^5,7

When it was made

The sources give different dates.^1,2,8 A June 1925 article in Asbestos on Prasco's history says the Prasco High Temperature Block was developed about two years earlier, but was not put on the general market straight away; at first it was used only where it could be carefully watched.¹ An insurance company's 1981 list of asbestos products, compiled from other companies' answers in lawsuits, gives Prasco as made from 1928 to 1957, and Fibreboard's report published by the EPA in 1990 gives about 1928 to 1957.^2,9 In sworn answers in a 1969 lawsuit, which asked only about products from 1940 on, Fibreboard said Prasco pipe covering, block and cement were made until January 1957.⁸ Yet Pabco's ads still listed Prasco 15 C pipe covering, block and cement, for temperatures to 1500° F, and Prasco 19 C block, to 1900° F, from May 1957 through January 1961.^5,7

What it contained

Fibreboard's 1969 answers say Prasco contained 85% diatomaceous earth and 15% asbestos.⁸ The 1981 list gives 15 in the column read as percent asbestos.² Fibreboard's 1990 report gives 85% diatomaceous earth and binders, about 15% asbestos, and says the product was yellow or red.⁹

Where it was used

The 1924 ad offered Prasco blocks for temperatures of 1000° Fahrenheit and over, for boiler casings, brick walls and breeching.³ The 1925 article recommended the blocks between fire brick and the outer brick or steel casing of boilers, on any part of a marine boiler, and on uptakes and breechings, and said they had stood up where pyrometer readings showed 1700 degrees.¹ It also described a steam pipe covering then being made with an inner layer of Prasco and outer layers of 85% Magnesia.¹ In 1930 the magazine reported that Plant Rubber had finished a large contract for the Great Western Company, with 85% magnesia applied over Prasco, in some places six inches thick.¹⁰

Pictures

How Prasco (Fibreboard) looked: a label, photograph or catalog page from our library. Each picture has its own page and library number, so it can be cited on its own.

• Catalog page: PRASCO High Temperature Block Insulation (The Paraffine Companies) and 1 other productCatalog page · ACL Doc 15218

Asbestos claims

If you or a family member worked with or around Prasco (Fibreboard) and later developed mesothelioma or another asbestos disease, a claim may be paid by the Owens Corning/Fibreboard asbestos trust (Fibreboard subfund). Free case review.

What each document says

Every statement about Prasco (Fibreboard) in the documents, in each document's own words.

Kind of product

We list Prasco (Fibreboard) with pipe covering and block insulation and insulating cement and coatings, from how the documents describe its form. Those pages explain how such products exposed workers.

Trades that worked with products like it: Insulators and Insulation Workers, Pipefitters and Plumbers, Boilermakers.

See also

• Fibreboard: the company's history, documents, people, products and plants
• Fibreboard on our products page: what the documents say about the company's asbestos products, with sources

References

1. Asbestos Magazine, 1925, June 1925 (June 1, 1925), pp. 18–19.
2. The Travelers Insurance Company's Product Information Booklet for Its Asbestos Seminar (1980–1981) (April 30, 1981), p. 7.
3. Asbestos Magazine, 1924, October 1924 (October 1, 1924), p. 41.
4. Asbestos Magazine, 1948, August 1948 (August 1, 1948), p. 31.
5. Asbestos Magazine, 1957, May 1957 (May 1, 1957), p. 63.
6. Military Qualified Products List (1951–1995) (December 3, 1951), p. 2.
7. Asbestos Magazine, 1961, January 1961 (January 1, 1961), p. 55.
8. The Potter v. Fibreboard Case File (1969-1972), Answers to interrogatories (December 22, 1969), p. 1.
9. Asbestos; Publication of Identifying Information (February 13, 1990), p. 7.
10. Asbestos Magazine, 1930, March 1930 (March 1, 1930), p. 53.
11. The Borel v. Fibreboard Case File (1969-1972), Answers to interrogatories (April 3, 1970), p. 1.
12. Sourcebook on Asbestos Diseases: Medical, Legal, and Engineering Aspects, Volume Two (1986), p. 101. Not yet published in our library.