Author: Camilla Barry

I'm a general science and nature teacher, with interest in many topics including history, ethnobotany, geometry and measurement. I try tying all those subjects into my lesson plans. I gave a TED talk about science teacher-training I did in Afghanistan, over a period covering 10 years and 12 trips. I have led many teacher workshops for organizations such as UC Berkeley, National Teachers of Mathematics, National Science Teachers Association, Girl Scouts of America, and others. I patented a protractor which makes life easier for students to understand angles and geometry, with lesson plans. I have a passion for learning!

Science yields clues to an ancient salt mine

Two Experiments Help Solve a Mystery

“Residents mined and traded salt” The sign offered little information, but I wanted to know more. Ruins of an ancient Anasazi settlement were huddled into a cliff above a sinkhole full of green water and leeches. “Where did they mine salt?” I asked a ranger. He directed me to nearby Camp Verde. “Look for Salt Mine Road and just keep driving. You’ll see white mounds.” So I was off.

Cliff Dwellings Montezuma Well, New Mexico

These mounds had been worked in historic times. Lumber and twisted railroad ties lay on the ground. I strode up the mound and scooped up the white powdery material, then tasted it. It wasn’t table salt as I knew it, but did have a taste of salt mixed with … something else. Dirt was liberally mixed with the salt. Was this material good for health? Was it sodium chloride (table salt) or something else? How was the dirt removed before eating? Or was it removed?

Crystal structure of sodium chloride could provide some clues. Common salt crystals are cubic. (Not in your salt shaker, as the crystals have been ground to a powder). As I continued to wander, I discovered a salt seep and water running from it. Where the water dropped over a rocky ledge, salty icicles hung. These were pure mineral so I broke off a few icicles and placed them in an empty coffee cup I was carrying. I would analyze these later. I peered closely at some crystal fragments drying in the sun. They weren’t cubic; the white crystals were slender needles. By the way, exploring can be messy. My feet sank unexpectedly into deep goo near the salt creek, leaving my shoe behind. I dug around for it; then walked back to my car with mud peeling off my legs. I washed off in what happened to be a historic irrigation ditch down the road.

Experiment: grow crystals

Here’s how to analyze those crystals and discover what they might be. You can do this experiment with many common substances: salt, epsom salts, sugar. Dissolve clean grains in pure water. Start with 1/2 cup of water and dissolve as much powder as the water will take. If you heat the water first, you will be able to dissolve more powder because hot water dissolves salts more easily. Stir until theThen pour the solution onto a cookie sheet with rims to keep it from running off. If you line the cookie sheet with black construction paper, the crystals will be more visible but that’s optional. Put the cookie sheet near a window where it will get indirect sunlight and wait for the water to evaporate. Crystals will be left behind. I learned the hard way not to put the cookie sheet under direct hot sunlight. Evaporation will proceed so rapidly that good crystals don’t have time to grow. But this could be another experiment! Put one tray in the heat of summer sun and another in bright but indirect light near a window. Compare the two.

Observe the shape of the crystals. If they’re cubic, you have sodium chloride. If it’s needles, you may have magnesium sulfate. (epsom salts).

Experiment: Clean dirty salt

If you don’t have clean crystals, you’ll have to remove the dirt first. How to do this? Dissolve the material, dirt and all, in water and pour it through a filter. I use paper towels or cloth in a colander. Then you can proceed as above. You can also try growing crystals using dirty salt/powder. How are they different from the cleaned substance?

How did the ancient Anasazi clean the salt? They had no paper towels, colanders, and possibly no cloth as we know it. Think about this. Perhaps they let the “salt” water solution sit in a pot until the dirt settled out, then poured off the liquid for evaporation. Did they have flat stones for an evaporative surface? Or did they mix the salty solution into their foods? Or eat the salt with the dirt included?

What were the effects of eating magnesium sulfate? This mineral is actually important for many cellular functions and is sometimes used as a laxative. There are rarely negative side effects from eating it, but using it in place of salt may have left a salt deficiency in Anasazi diets. Sodium chloride is vitally important for survival. If they weren’t getting it from the “salt” mine, what other sources of salt were available? Meat and blood are one source. Some desert plants contain salt.

NOTE: The term Anasazi is outdated, but I use it here because it is still widely understood. Today’s Hopi Indians are descendants of the “Anasazi” so ancestral Hopi is a better description of cliff dwellers at Montezuma’s Well.

Balance and Center of Gravity

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Vertigo: the sensation of spinning or whirling. The sensation can be associated with balance problems. A friend of mine woke up dizzy several nights ago. “I had trouble walking without feeling like I was going to fall down,” she said. Her doctor had diagnosed vertigo and given her some exercises to do. “Boring! Boring!” she complained with a chuckle.

“Maybe boring, but helpful,” said her husband who came in with his cellphone buzzing. It was an alarm to remind him when it was time for her to do her exercises. Calcium crystals in her inner ear had likely become dislodged somehow. They are critical in maintaining balance. Always ready with a joke, I shook my head rapidly back and forth: “Is this the exercise?” I asked. “Close,” her husband said. My friend demonstrated the real exercises, turning her head to the side and holding it in position for 30 seconds before turning it even further and repeating. “Just boring!” she groaned.

This started me thinking about balance and some experiments. These are geared with children in mind, but adults have fun doing them, too.

Are you in balance?

Stand with feet slightly apart. Are you in balance now? How can you tell? (you feel solid and fixed in position) Now stand on one leg. Are you still balanced? Perhaps, but not immediately. How can you tell you’re not in balance? What can you do, to help become safely balanced on one leg? You need to re-center yourself so that you are standing over your center of gravity or center of balance. Sometimes it helps to throw an arm to the side. Where is your center of gravity when you’re standing on two feet? (right down the midpoint of your body). Where is it when you stand on one leg? Why can it help to hold an arm out to the side?
Now try this (good party trick, too!). Tell a friend you’ll give them a sack full of gold if they can only pick it up without falling. Put the “gold” or other treasure on the floor and demonstrate picking it up. Simple! Can you do it, if you keep your knees straight and your feet unmoving? Yes. Now position them against a wall as shown, with the treasure in front of them. Ask them to pick up the treasure without bending their knees or moving their feet – or falling. It is impossible. Why? To discover the answer, watch a person carefully as they bend to pick up an object without the constraint of staying against the wall. What do you notice? How does your body change so that you keep your balance?

I led the previous experiment with a group of giggling Afghan students in Kabul. I offered them an American penny if they could pick it up. How they tried to cheat, laughing uproariously: moving away from the wall, using their arms against the wall to stabilize themselves. I let them each have the penny afterward.

Tight Ropers

Consider how type rope walkers balance themselves. Examine these photos to see how they do it.

Struggling to place himself over his center of gravity

In the lower two photographs, professional tight ropers use bars to broaden their mass and/or to lower it. Broadening your mass (spreading it out) makes you less likely to tip or rotate off your center of balance. Lowering your mass lowers your center of gravity, which is another method stabilizing yourself. When I was learning to roller blade down hills, I found myself naturally bending my knees to keep low to the ground. Lowering my center of gravity helped stabilize me. Weights on the end of tight rope bars aid in spreading and lowering the mass of the tight rope walker.

A caterpillar and balancing butterfly

Cut two of these patterns from medium weight cardboard. Shoebox cardboard is perfect but others will work, too. From one of the butterflies, cut out the center portion and decorate it to look like a caterpillar. Find its center of gravity and balance it on your finger. Then try balancing it by placing only its nose on your finger.
Color the remaining butterfly as you wish, or use a photo to color a butterfly you’d like to study. Find its center of gravity and balance it on your finger. It should be easier to balance than the caterpillar. Why? Then try to balance the butterfly by its nose on your finger tip. Can’t do it.
Tape a penny on the underside of each wing in the position shown. Now you should be able to balance the butterfly by its nose on your fingertip…your nose…your toe…your ear…a pencil tip. Why?
NOTE: It might be easier to download the pattern directly from: https://www.thinkingfountain.org/s/symmetry/butterflypattern.gif

Your built-in balance tools

We’ve discussed how distributing weight can help tight rope walkers balance. But of course those aren’t necessary for humans to run, jump, walk, stand, or even walk on tight ropes. Our hearing, sight, sense of touch and air movements all send messages to the brain. The inner ear sends its own messages. The inner ear has three canals, lined with hairs and containing fluid and calcium crystals. As you move, the crystals brush against the hairs. Get this: (amazing, I think!) One canal senses up and down movement of your head, one senses tilt, and the other senses sideways movement. How glorious is that?

So, back to my friend with vertigo. After a day or two, the condition went away. She had done her exercises as asked. Did the exercises get her inner ear crystals in the proper condition, or did time just do its healing work? I don’t know but I’m glad she’s feeling better. Now I’ll see if I can get her to undertake tight rope lessons.

Update: African long distance runners and center of gravity

Kalenjin runners from west Kenya, tend to have tall lean bodies which may help them win marathons. Their ankles, far from their center of gravity, are thin. It has been theorized that thin ankles make it easier for them to move their legs…as opposed to stockier body types that have thicker ankles. Allen’s Rule is a scientific theory that suggests people who live in warmer climates, such as the Kalenjin, have long thin bodies. People who live in colder climates, such as Inuit, have developed stockier bodies.

Catch Your Shadow

On the recent winter solstice (Dec 20, 2020) I asked a friend to help me capture my noon shadow.

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“How would I do that?” she asked.

I unrolled a length of black felt and gave her a piece of tailor’s chalk. “Follow me outside. But be quick,” I added. “Solar noon is about to happen.”

Shadows are so much fun to have in your drawer. I used to have an entire collection of them, which I would take to elementary schools. Those have been lost during my several home moves, so I decided to start a new collection. Now I asked my friend, “How long do you think my shadow will be?” “Well, it will be short since it’s noon. Maybe you won’t even have one.” She eyed my yardage. Then we went outside. I looked at my watch: 11:59 a.m., exactly solar noon.

I unrolled the fabric and stood so that my shadow fell on it. My friend began tracing it with the chalk. She had to move quickly because the shadow began shifting away from her tracing. Luckily, it was noon, when the shadow moves slowest. If we’d been working at sunset, she wouldn’t have been able to keep up. When I had caught sunset shadows for my previous collection, two of my children would trace frantically to beat the sun as it advanced and my shadow slid out from under me. “Oh, Mom,” they would complain. “Why do we have to do this?” I had interrupted their computer game.

This isn’t my real shadow; it’s a piece of felt fabric

On winter solstice, the sun carves its lowest arc across the sky. A low angle meant shadows would be longer than on any other day of the year. I’d purchased 3 yards of felt at the fabric store the previous night and even that wouldn’t be long enough to capture my shadow. I had to cut off a piece of fabric from the excess folded part and use it to extend the fabric. Even I was surprised at the length of my shadow: it was approximately 10 feet!

Now my friend’s husband Mike joined us. “What is the angle of the sun now?” he wondered. “Can you measure it from your shadow?” Yes, you could. My vertical body and the length of the shadow created a right triangle. The angle of the solar height could be computed from this. The angle cast by a stick and its shadow on a summer solstice several thousand years ago is the means used by Eratosthenes to calculate earth’s circumference. That will eventually be another lesson plan!

Mike took out his cellphone and used an app to find true north and we marked its line directly on the shadow for reference. I was surprised, but shouldn’t have been, to find that my shadow was pointing due north, directly toward the north pole. At noon in the northern hemisphere, shadows will always point true north, which is why taking noon sightings were so important for mariners in the days before geo-positioning satellites. (You can have fun confounding people by asking them if they can make their shadow reverse direction, pointing in the opposite direction. Often, they will try repositioning their body before they realize it’s impossible and then they will ask why it’s impossible. We all know that shadows move as the day goes on. Why can’t you get it to point south? North of the tropic of Cancer the sun is always to our south, meaning that shadows will always point northward)

Think of all the ways shadows can be used! Really, the list is endless. Sundials, moondials, Marsdials. Shadows give you an idea of the quality of light in pictures and are used to create realism in cartoons and paintings. As above, shadows can give direction and help determine latitude. Shadows have helped astronomers identify craters on the moon. Over 2000 years ago, Eratosthenes used a noon shadow at summer solstice to determine the circumference of the earth.

What is “solar noon?” That’s when the sun is at its highest point in the sky. It would be easy to say, “when the sun is directly overhead” but that’s not true on most parts of the earth. Where I live at latitude 38 degrees north, the sun will never be directly overhead. And, solar noon is rarely at 12:00 on our watches. Time zones have put our watches out of sync with the sun. To find the “watch time” that corresponds to solar noon, you can look at the NOAA website or merely google solar noon on the date in which you are interested. It was a coincidence of factors that made solar noon nearly the same as clock noon on this latest solstice 11:59 p.m.

What is “true north”? That is the line that runs directly to the north pole, or to the north star at night. It is not the same as magnetic north. because the magnetic north pole is to the east of the true north pole. True north is the one used for navigation. The difference between true north and magnetic north varies from place to place and is computed as an angle. At latitude 38 north, the difference is a whopping 15 degrees. Before cellphone apps, you could use a compass to find magnetic north, look up the angular difference on a table; then use a protractor to redraw the line. Of course, you can still do this. Pay attention to the direction of the angle! Since magnetic north is to the east, the true north line will be rotated to your left.

The best time to take standardized shadows is on the solstices and equinoxes, but any time is fun. Best to take each shadow at solar noon for accurate comparison among them. So much fun! Use felt because it doesn’t ravel when cut. I like to decorate my shadows with embroidery.

Teachers in Ghazni, Afghanistan learn about shadows in a workshop led by Camilla Barry

Make Litmus Solution

Here is a familiar science lesson. I include it here because it correlates nicely with a previous lesson about using alkali to process corn. An alkali is a caustic or corrosive substance such as lye or powdered lime that is added to soil. As a caustic substance, it can help break down the coatings on corn. As lime, it helps lower or neutralize the acid in some soils. Thus, two important uses of alkalies are to break down difficult material, or to react with acids.

A gentle alkali is baking soda. A dangerous alkali is lye. The difference between the two is their position on the pH scale. The pH scale rates the acidity or alkalinity of a material. High pH can burn your skin and mucous membranes. Low pH can be used in baking. But how do you know the pH of a substance? Litmus paper, purchased at lab supply stores or some garden centers, will give you a reading. However, you can make your own litmus solution. This lesson shows you how.

Commercial litmus paper is soaked in a solution of water and lichen species. When you dip the paper into a liquid to be tested, the paper changes color. Match the color with the key that comes with the litmus paper and you’ll discover the pH value, ranging from 0 to 14. Low numbers are for acids, high numbers are alkali, 7 is neutral. The more extreme the number, the higher the acidity or alkalinity. Different litmus papers have different color values, but the numbers are standard.

Here is a simple pH scale:

Make Your Own Litmus Solution or Paper

Chop or tear leaves of purple cabbage. Put into a large pot and cover with water. (Note: the water source could make a difference. Tap water is generally neutral, which is what you want. Well water may start off being alkaline or acidic, which will affect the results of your homemade pH test.) Bring the water to a boil; then allow it to cool. Strain out the cabbage leaves and discard. Keep the water, which will be blue. This is your litmus solution.

Distribute the solution among several clear glasses. Keep one for comparison. This will be your “neutral”, unchanged solution and it represents #7 on the pH scale. Add a small amount of a substance you wish to test, into each of the other cups and stir. The color will change due to the acidity or alkalinity of each substance. Pink to deep red are acid; green to yellow are alkaline, also known as “basic.” Arrange the cups in order of color on each side of the neutral cup and you have your own litmus color scale. Be sure to label each cup.

From left: vinegar, orange juice, neutral, hardwood ash, calcium hydroxide, lye

Make litmus paper

Soak paper towel strips in the solution and allow them to dry. The color changes are not as dramatic as the litmus solution. You can drop liquids onto the paper, or dip the paper into liquids you want to test. If you want to test a powder, or soil, mix it with water first. Again, make sure your water is neutral.

Standardizing your tests

It is impossible to be completely accurate with the cabbage juice indicator, but you can approximate the standard pH test. Test the items on the standard test (graphic above) and note the color you get with the cabbage juice indicator. Either take a photo of your solution and then write the pH number on the photograph, or try to match the color with crayons/colored pencils. Keep these for future reference.

Don’t be limited by the items on the standard pH scale! Try all sorts of powders and liquids you find around your house. So much fun!

An experiment that didn’t turn out the way we anticipated (but we learned something important):

I taught this subject to a group of Kabul university chemistry students. The class was held in a hotel conference center. I instructed students to get a large pot of boiling water from the hotel kitchen. The hotel kitchen had just finished serving lunch to students and staff. Students were delighted to learn they could make their own litmus solution because litmus paper was difficult to come by, but purple cabbage was readily available from street vendors. The indicator solution was rapidly made, but the test colors kept coming out wrong. Everything was testing too alkaline. I decided the human dishwashers in the kitchen hadn’t rinsed the pot sufficiently after washing. It still had soap residue in it, which is alkaline. I was somewhat insulting of their care in rinsing pots and thought ruefully of the lunch we had just eaten, cooked in those same pots. Then it occurred to me that the well water serving the kitchen – and all of Kabul – might be alkaline itself. I checked this with local geologists who told me that the famously good Kabul water came from wells sunk deep into limestone layers. The limestone filters the water but adds alkali to it. Then I asked a physician whether this could be a cause of kidney stones that many residents had. “Yes,” he said. “Alkaline water can cause them.”

Copper Doorknobs and Your Health

I was so excited by something I learned yesterday that I stayed up long into the night on my motel internet reading about it.

Here’s the back story. I’m traveling cross country looking for a new home and exploring along the way. In Arizona I stopped at Jerome, a once-ghost-town that is now an artist colony. Jerome was a copper mining town perched high on a mountain slope. Because the town began slipping down the slope, and for other reasons, a company town Clarkdale was built in the Verde valley below. Had to visit that! A sweet little town full of Craftsman homes built around a square…and a great copper museum inside the old high school!

The display that caught my attention was about copper’s ability to destroy microbes. Who’d a thunk? Maybe everyone else knew this. The museum curator told me that many metals disrupt microbes but that copper is possibly the best. A scholarly article I read explained that copper releases electrically charged particles (ions) when a microbe lands on its surface. A microbe includes viruses and bacteria. The ions punch holes in the surface of the virus and destroy the rna and dna inside, so it can’t reproduce. (See my earlier article about hand washing and the corona virus).

This is one reason some hospitals use copper doorknobs. The old high school itself had copper door knobs. Copper reduces infections. Why don’t more health centers use copper? It is expensive.

This article doesn’t yet include photos or citations because I’m using my iPad and I haven’t figured out how to paste them. I also can’t do experiments while traveling but here is an idea for an activity:

Moisten some bread and allow it to sit in a bowl for a few days until it is moldy. Then place some pure copper wire across part of it and see what happens. Is mold considered a microbe? I’m not sure. A piece of copper pipe or sheet of copper would be better. Why not use a penny?

Two similar recipes; vastly different health effects

My Dad, Clavis Hinshaw, also known as CJ

My dad, known as CJ, grew up on a poor farm in central Indiana. His ancestors had lived in North Carolina and he still thought of himself as a southerner. He spoke often of the food he ate as a child, no doubt carried along with his ancestors when they migrated from North Carolina to Indiana in what is known as “the great migration.” A staple in his childhood diet was cornmeal mush, or simply mush. Here is a recipe for it, adapted from the website All Recipes:

Cornmeal Mush:

1 1/2 cups Cornmeal, 2 1/2 cups water, 1 teaspoon salt. Put all three ingredients in a heavy pan and bring to a boil, stirring constantly to prevent burning. When the water has been absorbed and the meal all incorporated, remove from heat. Serve as a sweet cereal with cream and maple syrup or as a savory dish.

Simple! Now compare that recipe to a recipe called sofki, traditionally developed by native Muscogee Indians in the southern United States and eaten perhaps for centuries before encountering Europeans. This recipe is adapted from the website https://mvskokecountry.online/2018/01/21/osafke-safke/

Sofki:

Place about three pounds flint corn in a bucket of water and let stand until kernels are soft. Drain the kernels and pound in a mortar while still wet. Remove any large or hard chunks. Put the ground grains into a kettle with three times the amount of water. (1 part grains to 3 parts water). Bring to a boil, watching carefully to avoid burning and stirring as necessary. When the mixture comes to a hard boil, add kvpe-cvfke, a drop at a time until the corn turns a slight yellow. Continue to boil, stirring often, until the liquid thickens and the corn is soft. Serve as a sweet cereal or as a savory dish.

Both recipes use ground corn and boiled water to create a mushy dish. Can you spot the difference in ingredients? One recipe led to a widespread disease in the American south, and the other prevented it. The difference is kvpe-cvfke, the Muscogee word for hardwood ash water. The disease it prevented was pellagra.

Hardwood ash water is created by dripping and straining well water through a bucket of hardwood ashes. That water then has an alkali in it, sometimes known as lye. Adding lye water to the corn as it cooked unlocked a vital nutrient: niacin. You encounter corn treated with lye if you buy hominy or hominy grits in the modern supermarket. Regular corn meal has not been treated this way. That’s not a problem if you eat a balanced diet, but poor white southerners often relied on corn as a staple in their diets and may not have supplemented it with enough fresh vegetables or meat. Lack of niacin in their diets resulted in pellagra, a disease that could cause the “four D’s”: diarrhea, dermatitis, dementia, and death.

It is interesting to note that Spanish explorers encountered corn being prepared this way by Native Americans. Spaniards introduced corn and corn meal to Europeans and European Americans but left out the important alkali process, also known as nixtamalization. Indiana, where my dad grew up, was rich in the tradition of eating cornmeal products. Corn was easy to grow in the farmlands created by cutting down vast forests. Grist mills were common on the creeks and rivers, and were a source of income for mill owners. It was easy and relatively inexpensive to take corn left over from feeding the hogs, to the mill for human consumption.

The discovery of the benefits of niacin and the prevention of pellagra makes for interesting reading. During the early decades of the twentieth century, the source of pellagra was at first thought to be germs. But the germ couldn’t be found and infection didn’t pass from one person to another. Still, the germ theory held on. A researcher Joseph Goldberger discovered that a balanced diet prevented and cured pellagra, but searched in vain for the reason. His suspicions of diet-caused pellagra were scoffed at. In one set of experiments, he fed dogs a diet rich in cornmeal such as the diet pellagra sufferers ate. The dogs weren’t interested in the food, so he added brewers yeast to stimulate their appetite. Dogs who ate cornmeal supplemented with brewers yeast did not get pellagra; other dogs did. It turns out that brewers yeast is rich in niacin. The missing element had been found.

How did scientists learn that adding lye to corn releases niacin? That calls for more research on my part.

You can try both recipes above to explore taste differences, or you can buy hominy grits from the supermarket and compare it to regular cornmeal grits (often known as polenta). For a more authentic Hoosier recipe, buy coarse ground cornmeal from an operating gristmill. Polenta is an excellent and tasty dish and I certainly prefer the name to cornmeal mush. Just don’t eat it exclusively.

Do It Yourself

I drove to a local Mexican grocery store over Christmas and perused their goods. Many Mexican chefs cook up tamales for the holiday and they do it from scratch. This calls for corn which has undergone the nixtmalization process. I bought a bag of corn and a container of “Cal” displayed alongside. Cal is calcium hydroxide, used in place of wood ashes or lye, to treat the corn. Online information says that Cal is less caustic than lye and gives the corn a better flavor. In a sign of the times, none of the store clerks knew how to use these ingredients. The butcher, a man who spoke only Spanish, was able to confirm that I had the right ingredients, via an interpreter who was mystified by the entire exchange. I heard a customer laughing about the difficulty of buying canned hominy at groceries that didn’t cater specifically to Mexicans. She was buying a can, so I asked her if she knew anything about using cal to create your own. She laughed, “Oh, you’re asking the wrong person! I didn’t even know you could do it yourself. Good luck!”

Naturally, I wondered how Cal compared with hardwood ash and lye as a caustic agent. I bought lye from a grocery store (near enough: drain opener containing sodium hydroxide), Cal from the Mexican grocery, and (hardwood) walnut ash from my fireplace. Then I used the cabbage juice indicator test to find out which was the most caustic. See my lesson on that subject! NOTE: lye/sodium hydroxide is EXTREMELY POISONOUS AND CAUSTIC TO SKIN.

I followed the recipe (below) for treating the corn from the website “My humble kitchen.” It confirmed what the grocery store butcher had told me. (https://www.myhumblekitchen.com/2009/12/nixtamal-preparing-corn-for-tortillas/)

Nixtamal

Ingredients:

2 quarts organic field corn
5 tbls Lime/Cal
4 quarts filtered water

Method:

Rinse corn and remove any chaff. Drain through a colander.
In a non-reactive pot, mix water and lime over high heat until lime is dissolved.
Add the corn and bring to a boil for 15 – 20 minutes.
Remove pot from heat, cover, and let soak overnight.
The next day, drain the corn through a colander and rinse. If making hominy for posole, remove hulls at this time. The hulls are the little brown tips which can be rubbed or picked off.
Place corn in a bowl and cover with water. Allow to soak for 5 – 10 minutes moving the corn kernels with your fingers and then rinse again. Repeat this process one more time. This will ensure all traces of lime are washed away.
Drain the corn through a colander and you’re done. Homemade nixtamal!

Further resources:

Here is an excellent website about niacin, vitamin B3; it’s uses, etc.

https://www.healthline.com/nutrition/niacin-benefits#TOC_TITLE_HDR_5

And here is a recipe for substituting nixtamalized corn meal (pre-made, masa-harina) in a cornbread recipe:

https://www.thepioneerwoman.com/food-cooking/recipes/a99048/masa-harina-cornbread/

Take This Tarantula Field Trip Northern California

My husband David first read about the Mt. Diablo tarantulas in the San Francisco Examiner Sunday edition. With his characteristic vigor he exclaimed, “Got to go see them!” and within the hour we left with our three kids. It was October and that’s when male tarantulas go wandering to find mates. The day was hot, the folding hills of Mt. Diablo golden. “Look there!” David exclaimed as we drove up Northgate Rd. He had spotted our first tarantula casually crossing the pavement.

We crouched down on the centerline to admire it; then picked it up with cupped hands. Our youngest son Clive held his arm out so the spider could walk up it. We held hands underneath to catch the spider should it fall. We knew that tarantulas are not poisonous to humans and were highly unlikely to bite. Perhaps we shouldn’t have picked it up but we were careful and soon enough we set it on its way unharmed.

Clive, Jill and Nick had previous experiences with tarantulas. This one was in Costa Rica.

This is what I hoped would happen on my trip to Mt. Diablo yesterday. The hills were still golden in the autumn light, just as they had been before. An added delight was that the elevation was high enough that I was above the smoke line from the California wildfires. I did not see any tarantulas, although I did see a female tarantula nest. The silk surrounding the hole indicated that she was still inside. The silk makes it easier for her to slide inside and out. Had she already mated? I don’t know. I’d read that she puts a web of silk over her hole when she’s ready to mate. The male taps on this webbing to announce his presence.

I spoke to two park personnel about where I might see tarantulas. One told me “They are everywhere!” but the gentleman at the visitor center said he’d seen only one this year. “I think there are fewer tarantulas than there used to be. And now they seem to come out more in August and September than in October.” He added, “And they don’t like direct sunlight, so you’re more likely to see them in the evening or morning.”

I hiked several trails and stayed until after sunset, even briefly considering sleeping in my car overnight (outside the park entrance) to see if I found any early next morning. I hadn’t paid for camping, although I will next time. The campground was open and there were several vacant spots.

I would highly recommend this field trip, even though I didn’t see tarantulas. The park is lovelier than I remembered: vast acreage of beautiful oak covered hills and tremendous views from the peak. There are other reasons to go, too. I will talk about them on another post. Next year I will go in September and camp.

Capture Bugs with a home-made pooter

Bringing the forest to the classroom: exploring old logs with a pooter

I first read about pooters in a book by the famed English naturalist Gerald Durrell. A pooter is a tool for sucking insects into a vial where they can be observed. “Got to have one!” I said to myself. Plus, who wouldn’t love to say they’d gone pooting. A more scientific name for the device is aspirator.

Most supplies can be purchased at Tap Plastics or a brewing supply store
6 inch length of 1-inch diameter hard plastic tubing
8 inch length of flexible plastic tubing, cut into two pieces of 4 inch each
two rubber stoppers (with holes) to fit snugly into each end
small square of cheesecloth or window screen
Note: you can buy a length of hard plastic tubing and cut it on a table saw to 6 inches

Insert flexible tubing into the holes in the stoppers. Wrap the cheesecloth around the inside of one of the stoppers before shoving it into the tubing so bugs can’t get in your mouth. Put one end of the tubing over the bug you wish to observe and suck on the other end.

Pill bugs are excellent for observation, since they move fairly slowly and are easy to capture. Bring an old rotting log into the classroom and let children discover all the bugs hiding there. Bugs never seem to be injured in the process. They can be observed directly in the pooter or moved to another larger environment.

I have used pooters in many classroom and on field trips. Before I realized the importance of the cheesecloth, I swallowed at least one pill bug! However, during medieval times, people would swallow pillbugs intentionally, believing them to be medicinal; so I knew I would be fine.

A pooter similar to the one Gerald Durrell would have used

Chocolate Chip Levers

OK, the title is click-bait. You don’t need to use chocolate chips in this lesson but they sure are fun. I have used pennies or even beans. You simply need small objects that are consistent in weight and don’t roll.

Age level: PreK – third grade
Science Standards: for space considerations, these are addressed at the end
Materials Needed: 12-inch or cm rulers, tape, chocolate chips (or lentils, pennies, metal nuts, beans)

Levers are simple machines. That means they use few or no moving parts and can be the basis of more complex machines. Levers have been used since antiquity to lift or balance objects. In this lesson we will study teeter-totters and their kin to understand how they can be used to lift heavy objects with little effort.

Ancient Assyrians lift a stone colossus using a lever

Introduction

Identify the parts of the lever: lever arms and fulcrum. The position of the fulcrum is crucial. In the following drawing, the fulcrum is in the middle and two children of equal size balance each other. But what if one child is much larger than the other one? Or, a child wants to teeter-totter with her mother who weighs quite a bit more? In those cases, the small child might not be able to lift the larger person and the teeter-totter wouldn’t work. Think: How can this problem be solved? As students provide thoughts, ask them to draw their solutions on the board. Think about this question as you proceed through the lesson. Either the fulcrum must be moved, or the position of the people on the teeter arms must change (effectively changing the fulcrum) The teacher may or may not want to share the correct solution at this point.

Capturing student interest

Show photos of extraordinary levers at work, or levers that went awry. Or provide a discordant event (see “Fun with Students”, below)

The Activity

In this lesson, we will create a teeter-totter from a ruler; then use it to lift objects of unequal weights.

Step 1: Tape a 6-sided pencil firmly to a table.

Step 2: Balance a ruler atop the pencil. You have created a potential lever. Where are the lever arms? Where is the fulcrum? The ruler is 12 inches long. Where should you place the ruler so it is balanced on the pencil?

The ruler is balanced on a pencil fulcrum

Step 3: Only after the pencil is balanced (both ends off the table), give the students two chocolate chips. Place one chip on each end of the ruler-lever and rebalance it. Make sure the two ends are off the table. Ask students to note the length of each lever arm (6 inches and 6 inches)

Step 4: Only after the two chips are balanced, give the children an extra chip. Ask them how they can change things so that a single chip can balance (or lift) two chips. Tell them they must keep the chips on the end of the ruler (because you want to emphasize the position of the fulcrum and lengths of lever arms). The single chip should be on the “zero” end of the ruler for easier computation. Students should note the lengths of each lever arm.

Step 5: After students have discovered they can change the lengths of the lever arms, give them 3 more chips and ask them to balance a single chip against 5 chips. Remember to leave the single chip on the zero end and keep all chips as close as possible to the end of the rulers.

Assessment and Thinking

What did you do, to enable a single chip to lift 5 chips? (made that side longer). Point out that longer levers do more work than shorter levers. Another way of thinking: Pushing on the end of a lever provides more strength than pushing midway on the arm. Some manufactured levers are designed to remind you where to push.

Who can draw a teeter-totter correctly to enable Jane and her mom to use it?

How could you correct the situation of the poor donkey and his cart (above?) Lengthen the cart arms and put the donkey at the head.

Could an ant conceivably lift an elephant on a teeter-totter? How would you do it and why would it work?

Fun with students via a discordant event

Rigging the game. Before asking students to start the lesson, I make one of two rigged rulers:

Rulers painted unevenly, difference magnified for clarity

Use red and black poster paint to paint one ruler in two equal 6-inch segments. Paint a second ruler in the same colors but make one end longer – hopefully, not enough for students to notice on casual inspection. The line separating the two colors will be put on the fulcrum. Use the first ruler to demonstrate how to balance one chip against the other. Switch out the second ruler while distracting them. Then use a “super chip” from a special jar to lift more than one chip. Ask students to explain.
Use a regular ruler to balance two chips. Then switch that ruler with an identical one that has a penny taped to the bottom. In one case, a chip balances another chip. In the second case, with everything apparently the same, one chip will simply not balance the other chip. Ask students to figure it out. Note that unscrupulous merchants have rigged scales this way in the past. With modern laws and computerized scales this normally wouldn’t be a problem today.

Preschool children share a laugh at rigged ruler

Credits:
Etching of Assyrians and levers; Nineveh and Babylon – a narrative of a second expedition to Assyria during the years 1849, 1850, and 1851 by Sir Austen Henry Layard 1874

Donkey cart in Kabul; photographer known, google photos

Nail Clipper: Amazon.om

All other photos and drawings are owned and copyrighted by Camilla Barry, 2020

This lesson addresses many Next Generation core standards that carry through grade levels PreK – 12. Examples are (but not limited to):
Look for pattern and order in observations
Compare attributes of objects through measurement
Reason abstractly and quantitatively
Model with mathematics, Compare numbers
Use materials and tools to solve a specific problem
Analyze Data
Plan and Conduct an Experiment
Recall and gather information to answer a question
A problem can be solved through engineering
Multiple solutions to a problem are possible and should be compared/analyzed

Learn about spiders

October is a great time to observe spiders and their webs. Some of the best spider activity happens now, before the cold weather arrives. This lesson is suitable for PreK and K students, addressing many science standards; but adults should find it interesting, too. See the end of the article for science standards. Plus, spooky spider webs are part of Halloween lore.

Spiders are not the only insects to make silk (what other ones can you think of?) but they are the only insects that use silk to capture prey. Some spiders capture prey without proper webs, but this lesson is geared toward web-building spiders.

Spiders spin silk from a spinneret on their backside. A spinneret can make many types of silk ranging from strong foundation lines to elastic drop lines to sticky bug-catching threads. https://en.wikipedia.org/wiki/Spinneret

An orb web contains all these types of silk and is probably the most beautiful web. Here are the steps used in making this web. A teacher should draw these steps on a white board.

A spider atop a twig tosses a line into the wind, again and again if necessary, till it snags another suitable twig. (for an interesting folk tale regarding this, see https://anasebrahem.wordpress.com/2013/11/15/robert-the-bruce-and-the-spider-inspiring-story-never-give-up/ This is the first foundation line.
The spider walks across the foundation line, spinning a second thread.
She comes back to the middle of that thread and drops to the ground, taking it with her and anchoring it so there is a Y-shape.
The spider constructs a series of additional foundation lines and then radii from a central point. None of these are sticky silk.
Finally, the spider spins sticky silk around and crossing the radii. Here is a picture that might be helpful: https://commons.wikimedia.org/wiki/File:Orb-web_building_steps-01.svg If you stare at this picture long enough, you will begin to wonder about the missing steps. “Wait, ” you will say. “How exactly did the spider get from steps 4, 5, and 6? I don’t get it.” You are not alone. For a scholarly article see: https://www.researchgate.net/publication/256375822_Early_stages_of_orb_web_construction_in_Araneus_diadematus_Clerck

Now, read the delightful book A Very Busy Spider by Eric Carle. Pay attention to each step of the web-building process as the plot unwinds.

Activity #1: Make your own drag line. Cut a length of cotton string about 3 feet long and tie it through the loop in a safety pin. Pin the drag line to the back of your clothing at the waist line and drop it over your shoulder to keep it from tangling if you are with other student spiderlings. Tip for very young children: have them do it in steps: 1) extend string out on floor. 2) Pick up one end and put it through the small loop, keeping the string on the floor. 3) Have them cross one end of the string over, to make a loose loop. 4) Children or teacher finish the knot, or children help each other.

Even Young Children can contruct a drag line

Activity #2: Ballooning with the drag line. If there is a group of children, have them gather close together in a ball. Imagine they are about to be hatched from a silken egg sac created by their mother, all crowded together. They chew their way through the silk. Their immediate task is to get away safely from the other spiderlings which might be tempted to eat them. So they fling themselves into the air, dragging their line behind them. It sails out through the wind, carrying them far away to a landing spot. Children love running and throwing their drag line behind them. Author’s note: October 2019 I was kayaking on the Rogue River, Oregon, when we were surrounded by diaphanous silk from hundreds of ballooning spiderlings carried by the wind. It was glorious!

Spiderling Child “ballooning” across playground

Activity #3: Using a drop line. Some spiders use this method to escape predators. Pretend you are a spider gripping the center of your orb web. You are attached to the web with a springy drop line. If a predator (say, a bird) comes near, you let go your perch and drop to the vegetation surrounding your web where you will be hidden until the predator leaves in frustration. Then you give a small yank to your elastic thread and it bounces you back into your web. Children love doing this, especially if the teacher acts like a bird ready to catch them.

Activity #4: Go on a web walk. Before doing this, look at pictures of various types of webs spiders build. They aren’t all orbs. Some are triangle webs, tangle webs, funnel webs, sheet webs. Each one has its advantages based on location and type of prey. Look at shrubbery, around windows, under eaves and tables, near outside lighting. What types of webs do you see? Why are they built in that special location? http://ffden-2.phys.uaf.edu/webproj/212_spring_2019/Rose_Peters/rose_peters/spiderwebs.html

Activity #5: Capture a spider web to keep. This is a good activity for older children and adults. It requires patience and the willingness to try multiple times (see the folk tale about Robert the Bruce, above, about patience!). Sprinkle baby powder lightly on all parts of the web. Visually inspect the web carefully to find the foundation lines of the web. These are strong and your actions must break these lines without destroying the web while capturing it. Hold a stiff piece of black paper, larger than the web, close to the web. Position it carefully, then push the black paper firmly and quickly against the web, snapping the foundation lines while you do so. If you are successful, a beautiful web will be stuck against the paper, highlighted by the powder. You can store these webs between two sheets of photo protection, as from a scrapbook. Note: Try to take a web without a spider. Orb webs are often abandoned by spiders when they try a new location. Orb builders can build a new web in approximately an hour and collecting a web will not change their ability to do so.

Activity #6: Draw and write. Draw one of the spider webs you observed, with its surroundings. Include the prey that might be captured and the spider if you saw it. If you can’t go on a web walk, use what you learned from this lesson to draw a picture. Label the spider, the type of web, where you found it, and the prey. Date the picture. By dating your drawings, you will become more aware of when to look for spider webs.

California Science Standards Addressed (PreK and K):

K-LS1 Use observations to describe patterns of what plants and animals need to survive.

K-LS1-1 Use observations to describe patterns in the natural world to answer scientific questions.

K-LS1-1 All animals need food in order to live and grow. They obtain their food from plants or from other animals.

K-LS1-1 Scientists look for patterns and order when making observations about the world.

K-ESS2-2 Construct an argument supported by evidence for how plants and animals (including humans) can change the environment to meet their needs.

K-ESS2-2 Use a combination of drawing, dictating, and writing to compose informative/explanatory texts in which they name what they are writing about and supply some information about the topic.

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