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The History of Fiberglass

Feb. 04, 2024
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Fiberglass has become a ubiquitous product in today’s world. You almost certainly have several fiberglass products in your home (or even on it). In 2020, total global glass fiber demand totaled 10.7 billion pounds. And yet, just 100 years ago, total demand was about zero. 

So how did we get here? This post tells the fascinating story of the creation of fiberglass and how it became one of the most important industrial products. 

Before diving in, we should start by clarifying our terms. “Fiberglass” is actually used to refer to two distinct things. Sometimes, the term is referring to glass fibers, which can be found, for instance, in insulation. On the other hand, the term is also used to refer to the combination of glass fibers and a polymer matrix, like the fiberglass hull of a speed boat. A more accurate term for the latter is “FRP,” or “Fiber Reinforced Polymer.” We’ll use that term in what follows to avoid confusion.

Early Experiments with Glass Fibers

If you’ve ever had the chance to see a glassblower at work, perhaps you’ve seen molten glass being drawn out into surprisingly fine strands. There’s nothing particularly challenging about that. We know the ancient Egyptians, Phoenicians, and Greeks understood how to make delicate glass threads and would use them for decorative purposes.

But making some strands by hand and producing a large number of very fine glass fibers are two different things. In the 1800s, people in various places began to experiment with techniques for achieving this much harder result. The first patent in the US for the production of glass fiber was issued to Hermann Hammesfahr in 1880. He developed a cloth woven from glass fibers and silk.

His patent was purchased by Libbey Glass of Toledo, OH, which produced lampshades and a dress made from the cloth to be displayed at the 1893 World’s Fair in Chicago. The dress received a lot of attention, though commercial applications would have to wait for further developments.

A Key Breakthrough

Those developments came in 1932. The depression was being felt acutely by glassmaker Owens-Illinois, in Toledo, OH, as the economic downturn had lowered demand for glass bottles. Games Slayter, an engineer at the company, was working on ways to produce glass fibers as a strategy for finding new markets for glass. 

Another employee at Owens-Illinois, Dale Kleist, was experimenting with fusing glass blocks together using molten glass sprayed out of a gun originally designed for spraying molten bronze. When he attempted to spray the glass, however, the gun emitted instead a shower of fine glass strands. Slayter immediately saw the potential of this accidental discovery and honed the process of producing large quantities of glass fiber efficiently and cheaply, which was patented in 1933. 

The first product Slayter made with these new glass fibers was an air filter, which went on the market in 1932. This was to be the first commercially successful product made of glass fiber.

At the same time, Corning Glass of New York was also working on methods of producing glass fibers. The company approached Owens-Illinois to collaborate on research. In 1938 these companies formed the Owens-Corning Fiberglas Company (their name for the product had only one ‘s’), which continued to perfect techniques of industrial glass fiber production.

The Creation of FRP

Very soon after the discovery of methods to produce glass fiber in commercial quantities, engineers realized the potential to use it as a reinforcing material in a composite. The idea itself wasn’t new. Chemist Leo Baekeland, who invented the first synthetic plastic Bakelite in 1907, used asbestos fibers to reinforce the product.

During WWII, glass fibers were embedded in various resins to create the first examples of FRP using fiberglass. The early examples were used exclusively in military applications, particularly for aircraft parts. 

An important breakthrough came in the development of a polyester resin called Laminac, produced by American Cyanamid in 1943. Whereas previous polymers had to be cured with high heat, this polymer could be used and cured (using a hardener additive) at room temperature. This allowed for much greater flexibility in the fabrication of FRP.

Soon after the availability of this resin, the first FRP boat was built in Toledo by Ray Greene. In 1945, an FRP car prototype, called the Scarab, was built and driven across the country. In the 1950s, FRP using glass fibers gradually expanded into the range of products we associate with it today.

Fiberglass Today

The process for manufacturing fiberglass has changed a bit since the innovations of Kleist and Slayter. Their method of subjecting a stream of molten glass to pressurized air or steam is still in use, though in an updated form. The more common method of production involves forcing molten glass through tiny nozzles to create fine strands of glass, which are then drawn into a spool.

Different kinds of glass fibers are produced, depending upon the application for the finished product. The kind of glass fibers used in insulation, for example, are created in such a way as to trap lots of pockets of air in the glass. This has obvious advantages for a product used to insulate. Some types of class are created to have a higher tensile strength, while others are formulated to be especially resistant to certain chemicals or environmental conditions.

The most common applications of fiberglass are in the building industry. Most new houses are insulated using fiberglass batting and standard asphalt shingles also contain fiberglass reinforcement. 

In addition, fiberglass combined with resins is used in numerous applications where a strong, lightweight, and highly durable material is called for. This includes components in the auto and aviation industry, boat construction, sporting goods, storage tanks, shower stalls, and numerous other examples. 

FRP use in construction and industry continues to expand because of the useful properties of this versatile composite. At Tencom, we have seen this growth first hand as we have continually developed our expertise and capacity in the production of pultruded fiberglass products. If you’d like to hear more about what fiberglass can do for you, please get in touch.


Nick Gromicko, CMI®

and Kenton Shepard

Fiberglass is a type of fiber primarily composed of glass that is used in a wide variety of applications, and is predominantly employed as a residential and commercial thermal insulator. Fiberglass is also used to create products as varied as automobile bodies, boat hulls, arrows, roofing, shower curtains, and tent poles. As an insulator, it slows the spread of heat, cold, and sound in structures, cars and aircraft. By trapping pockets of air, it keeps rooms warm in the winter and cool in the summer, and thereby serves as a convenient method to increase energy efficiency. Fiberglass is an attractive choice for home insulation because it poses no fire hazard. According to some estimates, thermal insulation (made from fiberglass and its alternatives) conserves 12 times as much energy as is lost in its production, and it may reduce residential energy costs by up to 40%.


Glass has been woven into small amounts of coarse fibers for many centuries, even by the ancient Egyptians and Phoenicians, but fiberglass did not exist in its modern form until 1932 as a result of an accident. A researcher named Dale Kleist was attempting to create a vacuum-tight seal between two glass blocks when a jet of high-pressure air turned a stream of molten glass into fine fibers. He had unintentionally discovered an effective method to produce large amounts of fiberglass particles, a method that he would refine in later years. Fiberglass was trademarked in 1938 as Fiberglas® and was subsequently used in clothing, boat hulls, fishing rods, and eventually automobile bodies in 1953 when Fiberglas® partnered with Chevrolet.

In homes, fiberglass insulation can be installed in various parts of the building envelope. It can be pink, yellow, white or green, depending on its manufacturer, and has a spongy feel. Commonly found in blanket form, called batts, it is available in bags containing standard pre-cut lengths and widths. Batts are typically stapled into place. Fiberglass insulation also comes in bags as loose fill that can be blown into attic, wall and floor cavities. Most fiberglass batts are manufactured with a paper or foil backing that faces the direction of warmth. When installed correctly, it creates a continuous membrane that retards the passage of moisture and reduces the likelihood that fibrous particles will enter the living space. It is important that the backing always faces the warm side of the structure in which the insulation is installed.


Batts are available in different thicknesses, with the thicker batts offering a higher resistance to heat flow. This resistance is known as R-value, with common R-values for walls being R-11 to R-19, and R-30 to R-38 for ceilings.



When it is disturbed, fiberglass insulation releases particulates into the air that may be inhaled by those installing or removing it, or by property inspectors crawling through attics or crawlspaces where it is present.


If you must disturb fiberglass insulation, wear gloves, a long-sleeved shirt, pants, and goggles. A dust mask (or, for the greatest protection under any circumstances, a respirator with a particulate filter) should be used to prevent inhalation of the potentially irritating fibers.

Before removing fiberglass insulation, it is a good idea to dampen the area to prevent particles from entering the airspace. Afterwards, wash your hands with water – preferably cold water, as warm water can expand pores that can trap particles and allow them to travel deeper into the skin.

One Alternative:  Cellulose

Cellulose is a plant-based insulator and is the oldest form of home insulation.  At different times, it has been produced from sawdust, cotton, straw, hemp, and other plant materials with low thermal conductivity. Today, it is produced from recycled newspapers that are later treated with chemicals that reduce its ignition potential. 

Cellulose must be chemically treated in order to reduce its flammable properties, and such additives may have the potential to burn exposed skin or other membranes, so caution should be practiced when handling it.

Cellulose insulation is relatively inexpensive and significantly reduces air flow.  It is possible that the material can produce harmful off-gassing from the ink contained in the newspapers, but insulation is generally contained in sealed locations, so this is not likely to be a health concern. As is true with fiberglass, protect your lungs with a breathing mask when handling cellulose insulation.

Fiberglass and cellulose are both used as insulators, although they offer somewhat different advantages. There are also other types of thermal insulation available that are not covered in this article, such as rockwool, vermiculite, and various two-part foams. Insulation is an important part of enhancing a home's energy efficiency, lowering heating and cooling costs, and increasing comfort.





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