Thievery: The Mother of Invention

For generations, gypsum-based plaster has been cherished for its durability, beauty, and, of course, its ability to prevent crime. Joking aside, the first two characteristics are inherent qualities of what is essentially moldable stone, but the crime prevention only occurred with the addition of fibers to the mix.

The ancient Egyptians created a problem for themselves by making their burial coffins into desirable works of art. Thieves were tempted to invade a crypt and steal – not just the treasures that were sometimes buried with the deceased – but also the ornate sarcophagi themselves. After opening them and disposing of the current resident, they were resold in a morbid after-market

Plaster craftspeople knew that straw and grass fibers mixed with mud and clay increased the strength of bricks used in construction. They quickly seized upon the notion of adding fibers to their own endeavors and it became a most-effective deterrent for their corpse-containing plaster. Hacking into a linen or canvas reinforced sarcophagus destroyed it, making resale impossible.

The lessons of the Egyptians were never forgotten, and fibrous plaster was eventually put to use in other creations

What’s the Problem?

Tensile strength is a substance’s ability to being pulled apart. Like rebar in concrete or tendons in flesh, the tensile strength of fibers counters the natural brittleness of hardened plaster.

A crack is simply space between two fragments of plaster. Fibers prevent cracks by not allowing the space to form. The stronger the fiber, the heavier each fragment can be.

Test of Strength

Because fibers were, until recently, naturally sourced, their strength would be subject to many variations, local growing conditions and genetic differences among them. Most craftspeople learned through experience and error which fibers worked best.

It probably wouldn’t have been worth a plaster-worker’s time to devise a tensile tester like Leonardo Da Vinci’s clever device.

Build Strength & Lose Weight

Sheets of woven fibers were understood to be more robust than individual strands. But the weave needed to be suitably porous to allow plaster to penetrate and fully secure itself, much as plaster forms keys between wooden lathes in a wall or ceiling.

Despite fibrous plaster-work being centuries, even millennia old, it wasn’t until 1856 when a patent was developed in England. Gargantuan fibrous plaster ceilings became the standard in all British theaters.

Suspending such weighty decor was only possible because fibers, per unit of volume, are lighter than plaster. This lessened the amount of plaster used, further lightening the ornamentation. Gigantic pieces that would have crumbled under their own weight could now be manufactured and installed.