Do you ever wonder about the bumps on a piece of toilet paper? These raised imprints are called embossment, and I assure you, they serve a greater purpose than lending a more attractive look to tissue grade paper. Steve and I make it our bee’s wax to know all about toilet paper product detail, ranging from the mundane to strange. I never thought this paper piccadillio would be useful when discussing mimic engineering projects in a classroom. Hurray for unintended positives!
Inspiration for a new lesson often springs from the most unlikely of places. This one caught me unawares during our household’s dinner rush.
You see my son JB’s homework assignment was to read a couple of chapters from the book Ramona the Brave by Beverly Cleary. It’s our Monday ritual to read and cook dinner together.
I don’t know if you’ve read Ramona the Brave, but the gist of Chapter 4 is this…
- Ramona loses a single shoe to a German Shepherd dog while taking a shortcut to school.
- Ramona’s worried her teacher, Mrs. Whatsit, is going to be a pill about the whole thing. But surprisingly, she’s not!
- Ramona fashions a new shoe out of paper towels and wears it around for the rest of the day. 1st grade ingenuity for the win!
This is where the plausibility police received a 911 call from my son. Big brown eyes dripping with skepticism, right eyebrow cocked just like Daddy’s, my son looked up thoughtfully from the book. And out came the stream of consciousness:
“No way. No one could make shoes from paper towels, Mom. They would soak up any water on the ground! This is silly. How does this work? How do you make the water in paper go where you want it to go?”
I encouraged him to experiment, like a good mom probably should. I keep samples of competitors’ TP everywhere in the house. (Doesn’t everybody?!) He obliged. And while examining one of the rolls, JB pitched this out there:
“These bumps I see. What are these? Are they like the canals of Venice?”
All the “ahas” came right then. A lesson was born. Also, where the hell-o did he pull Venice out from?? By now, I had abandoned the stove and my hopes of cooking. It ended up being an eggs and expired frozen waffles kind of night.
After some digging, we concluded JB’s hunch was right. Venice and TP do have loads in common. Our experimenting continued with more TP, then progressed to paper towels and tissues. JB devised a system of simple straw drippers, and I found Blue Fanta that would best show where the moisture was heading. We tried saturating any type of paper we could get our hands on just to see how it held up with liquid and where it absorbed. All we had to do was follow the blue sugar water trail. The bumps--those embossed ridges--seemed to do the Venetian trick. The imprinted relief diverted the liquid where we wanted it to go.
Then we took to the books and the Internet. Here’s what I found.
Medieval Venetian engineers were working with marshy landscapes when they first laid out the city some thousand years ago. Over the centuries, the Venetians designed clever ways to fortify the foundations of their sinking metropolis. The most notable is the veritable forest of tree trunk piles, driven into the mud 10 feet deep, to bolster the 100+ islands they planned to connect. Concrete was poured over this mucky foundation. The mud encased the piles and preserved them like a bog mummy. Venetians later built their iconic bridges using Roman arches to make elegant walking connectors to each ‘concreted island’. It’s not unlike our modern concrete block foundations with rebar.
But most importantly, the Venetian engineers left room for the natural flow and valleys of the water that leads out to the Adriatic. They ‘channeled’ the water, carefully planning and controlling the watery streets instead of attempting to build over them. What remains is a modern engineering marvel that is still habitable.
Papermakers use this same concept of channeling when they add embossments, or raised imprints, on their tissue paper. The embossments channel the water so that the paper absorbs liquid where you want it to do so, spreading out the saturation rate for the rest of the paper surface. The effect is that paper with embossment will not fall apart as quickly as paper without the embossment.
Companies vary on which pattern they believe best absorbs and redirects liquid. Brawny favors a criss-cross, while Viva features concentric circles. Steve spent a looong time choosing our particular ‘Fleur de Lis’ pattern--and with good reason. The swirling pattern, like the fleur, is actually one of the most effective embossment patterns for wicking moisture. The Campus School 5th graders who we piloted this lesson with came to the same conclusion.
Scientists call this technique of shared construction ideas ‘mimic engineering’ or ‘biomimicry’. The best examples are the burr seed plants that inspired VELCRO. Also, Camelbak created a backpack drinking system based upon the thorny devil’s ability to chanel dew through grooves on its spikes and right back into its mouth. Crazy, right?!
Whatever the path, finding the analogy from one project to another is a great way to create something stronger, bolder, and new!
- Stephanie Roach, Recycling Educator