Educator How-to: Learn to Draw a Celtic Triquetra

At the Houston Museum of Natural Science, we know that people are as much a part of natural science as rocks and dinosaurs. That’s why we love social studies and maintain exhibits like the John P. McGovern Hall of the Americas and the Hall of Ancient Egypt. We find the development of societies fascinating!

The historical Celts, a diverse group of tribal societies in Iron Age Europe, ranged over a large swath of land reaching as far west as Ireland and the Iberian Peninsula, east to central Anatolia, and north to Scotland. The Celts used a three-cornered symbol, known as the triquetra, to adorn everyday items and important ritual objects. Similar tri-cornered symbols are seen in the artwork of many ancient civilizations. It is speculated that the symbol illustrates the uniting of the past, present, and future or birth, life, death. As Christianity spread through Europe, the triquetra was used to help new converts to understand the concept of the Trinity.


It is really simple to draw this ancient knot-work symbol. All you need is paper, a compass, an eraser, and some markers.

First, using a compass, draw a circle of at least 3 inches in diameter in the middle of your paper. Make sure to leave room around the circle, as the resulting knot will be slightly larger than the initial circle. Make sure that you do not adjust the compass after the circle is drawn.


Next, use a pencil to make a point on the circle at the twelve o’clock position. Then, place the point of the compass on this point and use it to make marks where it crosses the circle on each side.   


Now, place the point of the compass on one of the marks made in the previous step. It doesn’t matter which one. Then, draw a semi-circle within the initial circle. It should start at the twelve o’clock point and end in the lower quarter of the circle. The arc does not need to be continued outside of the circle. Make another arc, identical to the first one. The two arcs should cross at the center point of the circle. If they don’t, check to make sure that the compass setting has not been changed.


Then, placing the compass point on the lower tailing end of one of the arcs, mark off another tic on the bottom of the circle.celtic5


Now place the point of the compass on the bottom mark and draw an additional arc from side to side within the circle.


You will now need to enlarge the diameter of the compass a bit. Place the compass point back onto the marks made in the upper half of the circle. From each point, draw another arc within the circle, and extending a little beyond its border. It is important to make sure the arcs are extend a bit outside of the circle so they’ll meet up when the arcs are all drawn.


Pick a point where one of the knot strips intersects another, and make it pass over the other, erasing the lines from the underside from within the “over” strip. The next pass for the knot strip, following the same strand, will be to go under the next intersection, so erase appropriately. At this point ,you may erase the initial circle and the arc marks.


Now your trisquetra is complete! Color it in! See designs like this and others this summer in the Medieval Madness Xplorations Summer Camp.


Educator How-To: Cross-curricular Education Gets Cheesy

As educators, we all want students to understand the world holistically, but we still tend to teach each subject independent from all other subjects. Food is an effective way to capture the attention of students and provide a useful tool for creating a more global and cross-curricular learning environment. This global approach to learning has been shown to produce deeper understanding of the concepts being taught.

Making cheese, which seems on its face to be a fun break or a supplemental activity, can be used to discover important concepts and ideas that span an entire range of subjects.  These subjects include, but are not limited to, chemistry, history, and geography. Hands-on learning activities help to create interest and to create better retention of learned material.cheese meme

In that spirit, try one of my favorite activities. I use this activity at the Houston Museum of Natural Science to make learning and discovery memorable. It is a culminating activity for my Iron Age lab. It’s simple, affordable, and the kids love it! Why not give it a try?

A Little Bite of Cheesy History

Milk has been a major source of nutrition from the earliest of times. Milk is full of protein, fat, calcium and other important vitamins and minerals. It just so happens that it’s also full of water and sugars, which have no real nutritional value and cause the milk to spoil quickly without refrigeration. With the invention of cheese, man found an ingenious way to prolong the shelf-life of milk.

Because bacteria love a moist and nutrient-rich environment, milk spoils easily. In antiquity, there was no refrigeration, so unless it was cold outside, fresh milk could not be saved from day to day. No one knows how, but our ancestors figured out the trick to preserving milk. They discovered that calves have a substance called rennet in their stomachs that separates the milk solids and fats from the water in the milk they suckle from their mothers. We know that animal stomachs were used to transport and hold liquid, so it’s possible the milk turning to curds and whey was a fortuitous accidental discovery.


Goat stomach still used to make cheese in Sardinia. Photo by Ivano Atzori.

The first cheesemakers found that if they added some rennet to fresh milk, it would soon separate into two separate parts. We call these two parts the curds (where the good stuff is) and whey (mostly made up of water and some sugars). They learned that they could extract even more moisture from the curds if they cut them up and added salt to them, which also had the benefit of adding flavor to the cheese. Heating and pressing were also used to expel additional liquid from the curds. If left to age, molds and bacteria colonized the cheese, making it even more tasty! Thus was born an easy-to-make, non-perishable, transportable food for everyone!

Tasty Science: Make Your Own Ricotta!

Let’s get started! Here’s what you need:

  • 4 cups whole milk
  • 2 cups heavy cream
  • 1 teaspoon kosher salt
  • 3 tablespoons good white wine vinegar
  • Measuring cups
  • Measuring spoons
  • Pots
  • Hot plates (or a stove)
  • Mixing spoons
  • Large bowls
  • Sieves
  • Cheesecloth
  • Water
  • Paper towels

First, set a large sieve over a deep bowl. Dampen two layers of cheesecloth with water and line the sieve with the cheesecloth. Next, pour the milk and cream into a pot and stir in the salt.

Bring to a full boil over medium heat, stirring occasionally. Then, turn off the heat and stir in the vinegar. Allow the mixture to stand for one minute until it curdles. It will separate into thick parts (the curds) and milky parts (the whey).

Pour the mixture of curds and whey into the cheesecloth-lined sieve and allow it to drain into the bowl at room temperature for 20 to 25 minutes, occasionally discarding the liquid that collects in the bowl. The longer you let the mixture drain, the thicker the ricotta.

Transfer the ricotta to a bowl, discarding the cheesecloth and any remaining whey. Use immediately or cover with plastic wrap and refrigerate. The ricotta will keep refrigerated for four to five days.

This is a basic but tasty cheese and anyone can be successful in making it. If you decide to incorporate this activity into your classroom, please share your “cheesy” pictures with HMNS on Facebook or Instagram under the hashtag #HMNS. 

Educator How-To: Making the Moon out of Cheese (and Crackers!)

After months of renovation, the Burke Baker Planetarium at the Houston Museum of Natural Science will re-open March 11 with the best picture of the universe in the world! The Evans and Sutherland Digistar 5 digital projection system boasts the first True 8K image on the planet, with twice the resolution as an IMAX theater. The powerful digital software can zoom audiences to distant stars to see the universe from infinite perspectives, not just from the surface of the Earth. And with a tilted, seamless dome overhead and updated, comfortable seating below, the planetarium will be a must-see for Houston residents and visitors from literally anywhere.

But while it’s closed, life goes on, and without the incredible demonstration available at the planetarium to show the phases of the moon, explaining the orbit of our only satellite to kids (and keeping their attentions) can be a difficult task. So for hungry minds and bellies, we’ve got something to tide you over until the doors to the planetarium open once again.

Teach your students about the phases of the moon with this awesome Solar System snacking activity! I created this lesson plan as an alternative to the Oreo™ phases of the moon activity that we think is so clever. This science snack is a healthier alternative and will satisfy hungry students without the sugar rush. Educator How-To: Making the Moon out of Cheese (and Crackers!)

Moon worksheet


  • Ritz™ Crackers
  • American cheese slices
  • 1.5 inch round “cookie” cutter
  • Phases of the moon chart
  • Phases of the Moon worksheet
  • Markers
  • Waxed paper
  • Plastic knives

Educator How-To: Making the Moon out of Cheese (and Crackers!)

Moon phases


  1. Give each child a copy of the phases of the moon chart.  Go over the different phases, and consider using our Educator How-To: We’ll See You on the Dark (and Light and Far) Side of the Moon to demonstrate the phases in an active, hands-on fashion.
  2. Distribute one slice of American cheese to each student.
  3. Instruct students to carefully use the circular cutter to cut four circles from the cheese. With careful placement, one slice of cheese will be sufficient.
  4. Using a plastic knife, students will then cut one circle of cheese in half.
  5. The second circle will be cut using the circular “cookie” cutter.  Place the cutter carefully on the circle of cheese so that a crescent-shaped piece of cheese is cut from one side.
  6. The same procedure should be used to cut an additional crescent-shaped piece from the third circle of cheese.
  7. The fourth circle will remain whole.
  8. Now you are ready to go! Distribute the Phases of the Moon worksheets and have students place a Ritz™ cracker on each “moon.”
  9. Students will now arrange the cheese on the crackers to reflect each phase of the moon.
  10. When finished, students may eat the tasty moon snack!

Halloween How-to: Make a Spooky Skeleton Out of Recycled Milk Jugs!

Halloween requires skeletons. (And so does El Dia de los Muertos, for that matter…) If you’re on a budget but like to decorate, or you’re crazy about recycling, or you’re the crafty type who loves to add custom flair to everything, or you just want to see if you can do it, we’ve got a project for you!

Using recycled gallon and half-gallon milk jugs and some other simple materials, you can make your own reusable skeleton decoration to hang in your tree or around the house for spook season. Read through this easy procedure and watch our how-to videos for a clear example. Make one or make several, depending on how much milk your family drinks…


This homemade decoration is almost like the real thing! Photo by: Jason Schaefer


A minimum of nine plastic jugs – at least three of them gallon-sized


Hole punch

String, brads or pipe cleaners

Sharpie permanent markers or paint

Decorative bits (glitter, sequins, buttons, etc.)

Optional – High-temperature glue gun for punching holes


Three notes before you get started:

  • If you are making a second skeleton, you can probably use your jugs more efficiently than listed here and therefore need less.  If you are making this skeleton for the first time, I have asked you to provide 9 jugs (at least three of them being gallon-sized) so that you don’t have to work quite so hard to get a completed product.
  • The high-temperature glue gun works FABULOUSLY for punching the holes in the milk carton plastic, but I don’t recommend this method if you are a) working with younger children or are b) me because I absolutely burned myself. If you can get a volunteer in, they can sit and make the holes for the students pretty quickly.
  • If you are nervous about what you are doing, you can always sketch out your pieces with a Sharpie. Once you have them the way you want them, use rubbing alcohol to remove the Sharpie lines.
  1. Lay your hand or a template of a hand over the handle of one milk jug and trace.  Reverse the template or use your other hand for the second milk jug. Carefully cut the hands out. Save the extra bits.
  2. Repeat step one for the feet.
  3. Using a fifth and sixth jug, cut an extended oval out of jug around the handle, being as generous as you can with the oval. You can always trim it later! These will be the shoulder bones or scapulae. If you are clever, you can use the leftover bits to make your rib cage in step 9 as well.
  4. At this point, you should have two hands, two feet and two shoulder bones and a pile of left over bits.

    Where on the family tree would you place this skeleton? Photo by: Jason Schaefer

  5. Punch holes near the wrist portion of the hands and the ankle portion of the feet. Punch a hole in each end of the shoulder pieces.
  6. Using the leftover bits of your first six jugs, sketch out some bones. These should be basic stick shapes with lumps at each end. You will eventually need eight bones (four longer pieces for leg bones – two for each leg – and four shorter pieces for arms – two for each arm). Make them as long as possible. Once again, you can always trim them! In the example, my long leg bones crossed the jug diagonally to give them some extra length. With careful placement, I cut two long leg bones (and two knee caps) out of one of the leftover jugs.
  7. On a seventh jug, sketch out a skull (should consist of two large round eye sockets, an upside down heart or triangle for a nose and squares or ovals all lined up and touching for teeth). Use the two surfaces opposite the handle, and the jug should be upside-down. The neck of the jug will end up being the neck of your skull as well. You can add details as you see fit. It is also optional to cut the face out.
  8. Punch a hole in each side of the “neck” of your skull jug.
  9. Use your eighth jug to make a rib cage. You need to leave the neck of the jug as this will be the attachment point between the “hips” and the “ribs.”  That being said, cut out the handle of your jug so that there is a pretty big hole on one side of the jug.  This will be the front side of the rib cage. The neck and opposite side will represent the spine.
  10. To make the rib cage vaguely more accurate, cut some mostly horizontal strips out of the sides of the jug to leave the impression of ribs. The strips you cut out will become the empty spaces between the ribs. You will have to imagine that you are leaving a two inch vertical strip from the neck of the jug up the back to the bottom and down the front to the hole. This will act like the spine and the sternum. The horizontal strips you cut out should leave the two inch vertical strip intact.
  11. To make connection spots for the ribcage portion, cut two slits in the bottom of the jug on each side of the center. Then punch a hole on either side of each slit (for four holes total). Then punch two holes in the neck of the jug. If you are looking into the hole you created when you removed the handle, you will punch the one hole on the left of the neck and one hole on the right of the neck.
  12. To make hips, cut off the bottom of a ninth jug about two or three inches up. The example has a reinforced ring of plastic around the bottom and that was used to approximate the cuts. Round the corners of the jug and make the sides dip closer to the bottom of the jug.
  13. Punch holes in two opposite corners of the “hips.” 
  14. Cut a slit in the bottom of the “hip” piece and then punch two holes on either side of each slit (for four holes total). This is where you will attach your rib cage.
  15. Cut out two rounded corner squares from whatever leftover bits you have. These will be the kneecaps of your skeleton. Punch two holes in each that are opposite of each other.
  16. After you have everything cut out, you can make the parts interesting by drawing designs on all the bones in glow in the dark paint or Sharpie. Feel free to decorate your skeleton in either traditional Halloween or in the lighter and more decorative Dia de Los Muertos calacas style.
  17. Using a flat surface, align all the parts, making sure that you have the right connection holes punched out. Then connect all the parts together using the string, yarn or wire. Poke two holes in the top of the head and tie a loop that you can hang your skeleton from. From the top down, you should connect the pieces as such:
    • One shoulder piece to each side of the skull jug neck. Make sure they are facing the same way.
    • Tucking the ribs under the shoulder pieces so they stick out a bit, use the same skull jug neck holes to attach the rib cage. You will use the holes you created in the bottom of the rib cage jug to do this.
    • Connect your arm bones to each other and then to the shoulder.
    • Connect your hand to the end of the arm. Make sure they are facing the correct direction.
    • Connect the hip jug (bottom only) to the neck of the rib cage jug. You will use the four holes in the hip jug to connect to the two holes in the neck of the rib cage jug.
    • Connect the upper leg bones to the knee caps. 
    • Connect the knee caps to the lower leg bones.
    • Making sure they match, connect the legs to the holes in the side of the hip jug.
    • Connect the feet to the lower leg bones. Make sure they are facing the correct direction.