Almost everyone has used a glue one time or another and if you are someone very involved in art and craft, you must be using a glue almost regularly. Adhesives help us stick things together – from torn pages of books and to making a beautiful family collage. But have you ever wondered how it came into existence?
So far, the earliest evidence of glue is on cave paintings over 5,000 years old. We think that these ancient artists mixed glue with paint to help make the paint stick and protect their designs from moisture damage. It worked!
Early humans made good use of available materials to make glue. The hides, horns, bones, hooves, and some tissues from animals contained collagen, a tacky substance that was perfect for gluing some things. They also used brains and blood! Fish were also used to make glue. The skin and bones of fish produce a clear adhesive that wouldn’t show up when it dried. It is believed to be the first glue to be used for some photographic processes. There were also glues made from plants.
The curious inventors who gathered, mixed, boiled and processed animal and plant bits to make the perfect glue for the task at hand were some of our earliest scientists! The sticky goo they created could be used to glue things like pottery, utensils, and weapons. Later humans really got into gluing stuff. They used glues to create huge tile and glass mosaic floors, walls, and ceilings, and they used glue for all kinds of wood creations. Thousands of years later, many of these amazing and beautiful forms and structures are still intact, thanks to ancient glue!
Rabbit skin was also used to make a kind of hide glue that works well as a sealant and sizing for artists’ canvases, which prepares and preserves the canvas for painting. Rabbit skin glue was also used for things like bookbinding. Some folks even used animal glue as a sort of hair gel. Animal fat and beeswax have been found in the mummified remains of people who lived thousands of years ago.
Animal glues are still popular among furniture, cabinet and instrument makers because of their natural properties. Animal-based glues are also used for various kinds of restorations including the old paintings, frames, and furniture that benefited from them originally. Meanwhile, gelatin derived from cows and pigs is in stuff we eat! Marshmallows, gelatin desserts (like Jello), and pill capsules use animal gelatin. Blood glue from dried beef blood is popular for applications that need to be waterproof. It is used for tasks like bonding those little cork disks into bottle caps. Some plywood manufacturers also use blood glue to bond wood veneers together. At least we don’t eat that stuff.
Happily for animals, we have also figured out how to make adhesives from stuff created by animals without actually harming the critters. Some of these discoveries began thousands of years ago when people made glues from animal generated substances such as egg whites, milk, cheese, and beeswax. The egg whites worked great to glue down gold leaf for decorative manuscripts. The Romans used beeswax to fill the cracks between the planks of their boats.
Speaking of boats, if you’ve seen the bottom of one, you’ve probably seen a few barnacles. Barnacles are relatives of crabs and lobsters and have been around since Jurassic times. The adults are soft-bodied with a hard shell that protects them. Most barnacles live in shallow waters and attach themselves permanently to a structure such as a rock or shell, or even whales! They use their amazing cement glands for the sticky task. Scientists today are pretty interested in barnacle cement and are attempting to mimic the formula. The stuff is apparently stronger than epoxy cement and can survive salt water and very high temperatures without melting or cracking.
There are other recent discoveries about adhesives. A cool marine creature produces a gluey substance that is similar to a combination of spider silk and barnacle cement! The tiny animal has a big name, Crassicorophium bonellii. Other barnacles just ooze out their goo, but this creature spins out the stuff from a spider-like spinning duct. Crassicorophium silk is a very interesting discovery, and adhesive-loving scientists hope they can figure out how to make use of it.
Other scientists figured out that slug mucus is pretty remarkable stuff, too. Land slugs and snails have sticky mucus that helps them travel and protects their skin. Slug cells store the mucus in tiny granules so that it stays dry until it is secreted. When the mucus is exposed to moisture, it absorbs water, creating quite a slew of goo. Slug slime technology has lots of possibilities as a useful material in medicine and lubricants.
Probably the coolest recent adhesive discovery is thanks to a lizard. Tiny lizards called geckos can go just about anywhere, including straight up a window, without sliding! They can even walk on ceilings. What scientist wouldn’t want to figure out this feat of feet?
Geckos have millions of extremely tiny adhesive foot hairs on each of their toes. Every square millimetre of a gecko’s foot has something like 14,000 hairs, called setae. Each seta splits into hundreds of even tinier tips, so small that they are measured in nanometers. A nanometer is one-billionth of a meter, which means you need a powerful microscope to measure a gecko seta tip! The incredible microstructure in each gecko foot can attach and detach with little effort and can work on nearly any surface a gecko chooses to navigate, including underwater or in a vacuum. And unlike slugs or snails, geckos leave no slime behind. The hairs do all the work, so no other gluey junk is required.
But there’s more to a gecko’s ability to stick to glass. It took a team to discover that there is more to their little toes than just little hairs. The amazing ability to stick without glue also has to do with a gecko’s tendons and skin. These researchers used their findings to come up with a new invention based on gecko sticky feet, and called it “Geckskin.” This stuff is so strong it can be used to hold a 42-inch television to the wall. And it can easily be removed and reused. No sticky mess, no wall damage, and no need to replace with more Geckskin! Now, that’s some cool glue.
Ask your students all of the ways they can think of that adhesives are used in their everyday lives. What would they do without glue? You can even have them make their own glue if you’ve got access to a burner or microwave:
1 cup of flour
1/3 cup of sugar
1-1/2 cups of water (you might need a bit more or less)
1 tsp. of vinegar
Warm it up until it thickens a little bit, let it cool and start sticking!