Producing flame-resistant (FR) fabrics dates back to around 450 B.C. when textiles made from asbestos, which was known to have fire-resistant properties, were used to wrap the bodies of the deceased before they were placed on funeral pyres. Since these shrouds didn’t burn, they helped keep the ashes of the dead separate from the ashes of the fire.
In the centuries since, FR fabrics have taken a variety of forms, each with their own challenges. In 1821, Joseph Gay-Lussac discovered that treating fabrics with ammonium phosphates and borax made them somewhat fire retardant, but this treatment washed out of clothing too easily. During World War II, another flame-resistant finish was developed, but this one added significantly to the weight of the fabric. Other finishes, developed later, weakened the fabric instead.