B&W Fiberglass News

How is Fiberglass Made?

Posted by Craig Barry on Feb 9, 2018 9:44:00 AM



The early 20th century saw the advent of commercial-scale glass fiber manufacturing, but the process of melting and stretching glass fibers had been in practice since the time of ancient Egypt. Today, fiberglass yarn is one of the most widely-used textile reinforcements in the world, and the production process is improving every year.

If you’ve ever wondered exactly how glass fiber is produced, read on.


Before the Process: Selecting the Sand

There are many different kinds of sand compatible with so-called “textile grade” glass fibers. Most glass fiber is made from silica (SiO2) sand which melts at 3218 degrees Fahrenheit, although the melting process must be very tightly controlled. If silica is cooled too rapidly, its crystalline structure turns the material into quartz instead of glass.

For the most part, silica sand is almost always combined with other materials during the process of making glass fiber and yarn. E-glass, for example, a combination of silica, aluminum oxide, calcium oxide, and magnesium oxide, is more alkali resistant than pure silicon glass. E-glass is commonly used for sensitive applications such as electronics. Conversely, S-glass (E-glass + boron oxide) is more apt to perform when high strength is necessary.



During the initial “batching” process, all the components that will be melted during the glassmaking process must be carefully selected and weighed. In high-tech glass yarn making facilities, the batching process is almost always automated to ensure consistency across lots. Once thoroughly mixed, batches are stored in what’s colloquially known as the “batch house.”



Most glass fiber is melted within a natural gas furnace. These furnaces are divided into channels that allow the melted glass to flow; section one is for initial melting, section two for refining, and section three for extraction. During the extraction process, molten glass is extruded through bushings that turn them into miniscule lengths of fiber.



The processes of extrusion and attenuation are what create glass fiber yarn. As the molten glass is extruded through bushings in the furnace, water jets cool the filaments themselves. Attenuation is the process in which fibrous streams of glass are mechanically tensed, forming the actual glass filaments.



In some cases, a chemical coating (often known as a “size”) is necessary to adjust the characteristics of the glass filament. Lubricating coatings are used to protect the filaments from breakage during the winding process. Coupling agents can be used to improve the process of resin wetout later on. Size chemistry is critical to the ultimate performance of the glass yarn.



Once all filaments are coated, they’re typically collected in a bundle of anywhere from 50-1600+ filaments to form a strand. These still-wet strands are spooled onto a drum package on which they are then dried in the oven, then packaged for further processing.

The process of making glass fiber has changed both immensely and not at all over the past 100 years. Technology is advancing capabilities and improving throughputs every single year, but there is still a lot of human skill required in creating high-performing glass yarn.


B&W Fiberglass has been a leader in glass fiber technology for decades, and we’re not slowing down. Our partners bring to the table some of the most novel technological advancements in the glass fiber industry.


Want to learn more about our production process and capabilities? Reach out to the B&W team today.

Topics: Custom Glass Fiber, Glass Yarn, Fiberglass, Glass Fiber Threads