Holiday How-to: Chocolate Leaves

My mom was a chemistry and home-ec teacher, so I grew up in a home where ingredients were carefully measured and food items were attractively arranged. While I got to help out in the kitchen as much as I wanted, I always liked being in the kitchen around the holidays. There were always new tricks or special touches added to dishes and along with these came short science lessons on why we were doing things that particular way.

One of my favorite things to help with in the kitchen were chocolate leaves. When done correctly, these are perfect little molds of the living leaf, just like the perfect molds and casts in the Morian Hall of Paleontology.

A chocolate leaf is made by smearing melted chocolate onto a leaf and putting it into the fridge to harden. Sounds easy, right? It is pretty easy. Read on!


Activity: Chocolate Leaves


Leaves (*See note in step 1.)

Chocolate candy melts

Parchment or wax paper

A cookie sheet or plate for your leaves to rest on as they cool


1. Pick your leaves. I like to use slightly waxy leaves so you don’t have to worry about fuzzy bits in your chocolate. NOTE: Learn about the plant you are picking leaves from before you decide to use them. Many household plants are decorative but poisonous.  Oleander is a great example of a plant that is pretty but poisonous. If you hate botany or don’t know about the Internet, getting pre-packaged basil or mint from the grocery store is a safe way to go. These leaves will be a little less firm, so you will need to be more careful with them.

2. Don’t pick leaves from poisonous plants. Seriously.

3. Wash your leaves with soap and water, rinse them thoroughly and then dry them completely. The chocolate won’t stick to wet leaves, so don’t rush this step. You will only be frustrated.

4. Put wax or parchment paper on a cookie sheet or plate. You want this to be something that will fit in the fridge with no problems.

5. Get out your candy melts. The melts come in a hundred colors. We are using chocolate colored ones in this tutorial. There will be instructions on the package on how to melt the specific brand of melts you purchased. In general, you will put the melts in a microwave safe bowl and microwave them a few seconds at a time stirring as you go. Don’t overheat the melts. They get gross and there is no coming back from that.

6. When you have everything melted and creamy, hold the leaf by its stem. I like pinching it between my thumb and index finger and then using my middle and ring finger to support the leaf. Do what feels comfortable to you.

7. Dip your stirring spoon into the chocolate. Use the BACK of the spoon to spread the chocolate on the leaf. Make sure the chocolate is thick enough that it won’t break when you try to peel it. Place the leaves on the parchment as you work, and don’t let them touch.


8. The side of the leaf you use is up to you. If you are using mint and you put the chocolate on the back of the leaf, you will have some crazy patterns.  If you want something more subtle, use the front of the leaf. Coat the leaf almost to the edges. If you go too far, you will get ugly edges that are hard to peel. But don’t worry! Those leaves are the best to eat.

9. Put the tray of leaves in the fridge and wait a few minutes.


10. When the chocolate is set, peel the leave off the chocolate. You should have a perfect little mold of your original leaf. This may take a little practice. Work quickly as you have something designed to melt with heat in your hot little hands.

11. Done! You can store the leaves in the fridge until you are ready to use them. If the leaves got soft when you were working with them, put them back in the fridge to firm them up. Once they are firm, you can toss them in a plastic container.


Okay! So what’s the science here?

The word “chocolate” comes from the Nahuatl word Xocolatl for “bitter water,” referring to its original incarnation as a hot, spiced beverage in the Mayan and Aztec traditions. Traditionally, chocolate is a mixture of cacao powder, cocoa butter, and a sweetener. To make chocolate palatable and stable, we now mix milk solids, added flavors, modifiers, and preservatives.

Those candy melts? NOT CHOCOLATE! In this example, they are sort of chocolate colored, so they have that going for them, but they also come in a bunch of colors that are not known to nature so… not chocolate. They are mostly made of sugar and vegetable fats – not cocoa butter – and depending on the brand, they may throw in a little wax for better melting. Mmmmm… wax.

The advantage to the melts over the regular chocolate is that they do have the wax and the vegetable oil in them, which makes melting easier since the chocolate doesn’t need to be tempered. It hardens pretty quickly and sticks to whatever you dip in it, so it makes a great coating for cake pops or whatever crazy things show up on Pinterest this month.

Want to get super nerdy about your chocolate?  (I assume you do…) MIT has these tidbits available.

What’s in typical chocolate?

  • 10-20% cacao
  • 8-16% milk solids
  • 32-60% sugar
  • 10-20% cocoa butter
  • 2% theobromine and polyphenols

Cocoa Butter Chemistry

Fats and oils are organic molecules made up of three fatty acids chemically linked by an ester bond to glycerol. Fats are solid at room temperature, while oils are liquid.

Cocoa butter fats are made up predominantly by three major fatty acid molecules: Palmitic Acid, Stearic acid, and Oleic acid.

Oleic acid is unsaturated (has a double bond on its carbon chain), making it kinked and unable to pack well with other molecules. Because of this, a greater portion of oleic acid in the fat results in a lower melting temperature for the cocoa butter.

Chocolate makers can adjust the amounts of each fatty acid to produce a chocolate that melts only in the mouth, giving it a superior quality.

Tempering chocolate

The cocoa butter in chocolate can have several different crystal structures (three-dimensional patterns in which the fat molecules pack). There are six known chocolate crystal forms, or polymorphs. You can obtain each form by varying the fatty acid ratios and the temperature at which the chocolate is tempered (cooled).

Only a few of the polymorphs are considered good for gourmet chocolate because they give the right blend of snap (when you bite into the chocolate) and melting (when it warms up in your mouth). Melting is especially important because it controls how well the chocolate disperses and releases flavor onto your tongue.

Whether you will be constructing culinary masterpieces this fall or sitting back and enjoying the kitchen creations of others, we hope you have a happy holiday with you and yours!  (And when you’ve had a little too much togetherness, we will be open on Friday…)

Thank an archaeologist for human history on International Archaeology Day!

On Oct. 17, we celebrate International Archaeology Day. Last year, the Houston Museum of Natural Science participated on a large scale for the first time in a long time. This year, we will have our “Second Annual” version of the same. So what is archaeology and who are these characters that practice the art of archaeology anyway?

Ask anyone and they will answer “Indiana Jones!” when asked to name a famous archaeologist. Hollywood and the media in general tend to gravitate to this entertaining, but totally off the mark, representation of what it is to be an archaeologist.


Archaeologists are people who study the past. They do so with one goal in mind: reconstructing what our ancestors were up to. In the end, while we might find broken pottery, stone tools, or more sophisticated or larger artifacts, what really counts is the answer to questions like these: Who made this? Why? How? How long ago was this?

It takes a special person to be an archaeologist. Patience truly is a virtue. Doggedness comes to mind as well. It won’t hurt to be lucky, but having knowledge will guide you to that breakthrough you’ve been looking for. You’ll need willingness to continue learning, going hand-in-hand with the admission that you really don’t know all that much. All of these are good traits to have.

Luck is part of all this, but the insights archaeologists come up with and share with all of us can be a whole lot more interesting and head-scratching than any Indiana Jones movie. In that regard, archaeologists are like time travelers, our contemporaries who bring ancient cultures back to life, sometimes so much so that you can almost feel it and smell it.

Recently, I’ve been reading up on the presence of early humans in what is now called the Amazon rainforest. My perception of the prehistory of this huge area is changing quickly. Yes, there were early settlers in this part of the world. Paleoindians did reach Brazil, Bolivia, Peru, Ecuador and the Guyanas. Our knowledge of these early immigrants in this part of the world is so small compared to what we know of North American Paleoindians. But… all that is changing, thanks to the determined efforts of a handful of archaeologists, the very same people whose work and insights we celebrate on Oct. 17.

Take Dr. Anna Roosevelt, for example. A professor at the University of Illinois in Chicago and a curator at the Field Museum in the same city, Dr. Roosevelt has been investigating early human presence in the Amazon for decades now. The information she and her team have uncovered now point to an Amazon region that was very different thousands of years ago — well before the arrival of the Europeans. It was so different that these Amazonian Paleoindians would have a hard time recognizing the current landscape, just as much as we have a hard time coming to grips with the existence of large, densely populated settlements in many portions of the Amazon.

Marajo Island - location (2)

Map of Brazil, with the location of Marajó Island.

To get to this point, Dr. Roosevelt and her colleagues worked for years in the Amazon, in places like Marajó Island as well as rivers further inland. Marajó, an island the size of Switzerland located at the mouth of the Amazon River, yielded evidence of densely-populated settlements, occupied for centuries. This research took years to complete in circumstances where creature comfort was sometimes a distant notion. It took perseverance as well, as the new data and new interpretations ran counter to older, more established explanations of the prehistory of the region. Research in the interior relied on the willingness of non-archaeologists to share news of interesting finds on private properties. Sadly such willingness is not always forthcoming, resulting in the loss of an unknown quantity of materials all over the world.

Building trust among the locals and upholding that reputation is not easy. One has to be determined, focused and dogged in the pursuit of knowledge. Dr. Roosevelt’s team checked off all these boxes, and came up with cool finds, some on land, some underwater.

Diving in the Xingu River, 2001

Archaeologist Dr. Anna Roosevelt diving in the Xingu River, 2001.

On International Archaeology Day, we pay homage to the work done by people like Dr. Roosevelt. Local archaeologists, professional and avocational, physical anthropologists, and artists who work on facial reconstructions will all be at HMNS. Museum docents will share their insights and enthusiasm about archaeology with hands-on experiences, pointing to the various halls in the museum where archaeology is covered. These include the John P. McGovern Hall of the Americas, the Hall of Ancient Egypt and the section of human evolution in the Morian Hall of Paleontology. The event starts at 10 a.m. and ends at 4 p.m. Dig it!

Spider Crimes: the Worst Halloween Decorations on the Shelf, Scientifically Speaking

by Melissa Hudnall

September comes and I am shaken to the core with fear. I know what’s coming. No, I don’t mean winter, I mean another year of dismembered bodies and deformed figures. Can I handle the pain in their hurt eyes? Then it happens; I see the first hint of a hairy leg. My trepidation is high as I round the corner to see…



Kill… mmeeee…

I am infamous among my coworkers for getting just as upset as I am excited to see Halloween decorations going up. I adore Halloween, but I also love spiders, and this is where my conflict lies. Halloween does not love spiders. I have used my own tarantula so you can compare real treat to the tricks sitting on the shelves.

Let’s go over some spider basics so you too can feel my pain.


Pay attention to the pedipalps and chelicerae; you may not see them again. Pedipalps are for mating and holding food, and chelicerae house the venom and end in fangs, so these are important body parts. Going without these four appendages is like missing your arms, jaws and teeth.


First off, spiders have eight legs. Count the green circles. Only those are legs. Everything else, not legs.


So basically, I ate this cookie to remove this abomination from the world.

Secondly, they have two body segments — not one, not three. The legs are also attached to the front segment, not the back! The front is the cephalothorax, meaning “head thorax” and the back is the abdomen. Attaching the legs to the back is the same as having a leg growing out of your stomach.


I’m going to assume that these were not meant to be spiders with three segments, but rather very clever spider-mimicking ants. If you can have ant mimicking spiders, then surely it must work the other way around.


These look like ladybugs hitching rides on top of spiders.


And come on, people. Even dogs have standards. This chew toy is sub-par.

Lastly, have you ever tried your hardest and just barely missed your goal? I feel like this next spider embodies that moment. He has the correct number of legs, segments, pedipalps, chelicerae, and they’re all attached in the right places! However, SPIDERS DO NOT HAVE BONES!


*Drops the mic.*

Editor’s Note: Melissa Hudnall is a Programs Facilitator for the Youth Education department at the Houston Museum of Natural Science.


Skulls, Horseshoes, Parrots and Robots: Fall Teacher Tuesdays offer awesome classroom ideas

It’s officially fall, and I’d like to say the weather is cooling down and the leaves are turning bright and beautiful colors, but we live in Houston. So… no.

Instead, I can tell you that we’ve been hard at work this summer developing fun, fast and hands-on activities for this year’s ExxonMobil Teacher Tuesdays. For adults only, Teacher Tuesdays offer fun and interactive professional development opportunities for ideas to kick your lessons up a notch. We’re pretty excited about the line-up this fall, and we’re dying to give you a sneak peak of what to expect.


Our first ExxonMobil Teacher Tuesday has us focusing on one of our favorite topics: Day of the Dead! With all-new crafts, this workshop is sure to be a crowd-pleaser. Check out the photo above for a hint at the items we’ll be making in class. For those of you who have been to a Day of the Dead workshop before, you’ll be pleased to know that the sparkle box is back!


In October, you can join us for an in depth look at the rock cycle with James Washington, Lead Concierge here at HMNS. James, who leads tours for the museum, has his very own collection of specimens he’s willing to share with the world. Anyone who has participated in what I refer to as “The James Washington Experience” leaves with a much better understanding of how all sciences are connected.


You also have the opportunity to visit the new Hamman Hall of Coastal Ecology on Oct. 27 to discover the critters in and around the ocean. You’ll even get the chance to get up close and personal with a horseshoe crab. (Fun fact: horseshoe crabs keep you healthy in ways you probably don’t even know about but will learn in this mind-blowing workshop.)


For November, pop down to the rainforest as you learn about the Amazon in the Out of the Amazon workshop. As part of the workshop, you will be treated to a rainforest wildlife presentation as well as a tour of the new exhibit Out of the Amazon. Dover and Frankie, our resident green-cheeked conures, might even make an appearance and will within minutes have entire room full of adults trained to do tricks.teacher7Join us in December for a viewing of Robots 3D in the Wortham Giant Screen Theatre. HMNS’s own Kathleen Havens wrote the curriculum for this National Geographic feature, so you know it’ll be hands-on, fun and engaging for students while covering STEM objectives and careers. If you’d like to discover some reasonable engineering challenges you can do at school for your elementary and middle school students that don’t require a $3000 grant, this workshop is for you!


And that just takes us through December! The spring semester is just as exciting, covering everything from blood splatter to brain-based learning. Check out our complete schedule, and we’ll see you at HMNS!