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…)

With Soil, Make Me Wine: The Dirt on Growing Great Grapes

I like wine. And I make my own. Not huge batches, mind you. Just about 30 bottles per month in the winter months. I learned the hard way the chemistry of wine. If you let the wine get too hot while it’s fermenting, it can radically alter the taste.  I let one of my batches get above 95 degrees a few times this summer. I was making a port and the flavor was ruined. The entire batch came out tasting like welches grape juice. Flat, tasteless, 20 percent alcohol-by-volume grape juice. I only inflicted a few bottles on my friends.


Good wine is a combination of science and art. There is the botany of the grapes. The meteorology of the climate. And the pedology. What’s pedology you ask? It’s the study of soil.  And since it is the International Year of Soils, we are going to get down and dirty with the effect of soil on one of my favorite drinks.

The ground beneath us is incredibly active. There are millions of different types of bacteria, fungi, and arthropods that give dirt everywhere its characteristics. If you’ve been taking the museum’s class on gardening and landscaping, you’ll understand the importance of the health of soil for plants. To briefly sum it up, good soil makes good crops. A shocking concept. But beyond that, what effects can the soil have on wine?


The effect of soil and climate on wine is called terroir. Wine tasters with a good palates say they can discern the flavor of the soil in the wine. Scientists have begun to examine a comparison of terroir to wines in an attempt to explain this phenomenon but so far have not been able to. That doesn’t mean that the flavor of the soil isn’t in the wine; it just means more scientists will have to drink more good wines. That’s a study I want to be a part of!

Good soils will encourage the vines to produce grapes instead of growing more vine. So the best soils need to provide lots of water at just the right time and then be able to drain it away. And the soil needs to keep the right nutrients such as nitrogen and potassium available to the vine, which can help intensify the flavors in the grape.


Tasting wine is about more than just “good” or “bad.” With an entire family of varietals out there in the world, it’s about what gives the wine its identity. Fans of wine, like me, like to get closer to the wine and the wine-making process through the quality of its flavor. And, oddly enough, tasting isn’t just about the taste. Wine Folly offers a five-step process to tasting wine, and explains a few things to be aware of. Here’s the basic process outlined in their blog.

  1. Look at the color. This goes deeper than just red and white. Ask yourself how it compares to other reds or whites in color. Gauge whether you can see through it. With practice, you can gauge whether the wine is bold, rich or viscous.
  2. Smell the wine, but swirl it around first to aerate it. Put the wine on the table and move the base in little circles, then shove your nose into the glass and take a big whiff. What do you smell?
  3. Taste the wine. Get enough of the wine to coat your entire tongue and roll it around in your mouth to maximize contact with all your taste buds. Don’t just think about flavor; think about texture and body, how it feels in your mouth. Does it have an alcoholic burn? Do the flavors match the smell?
  4. Decide whether to spit or swallow. You may have to drive later, or you may have 20 wines to taste and want to stay sober enough to think about all of them. If you hate the wine, spit it out. If you don’t want to waste it, swallow it. There’s no right or wrong choice.
  5. Think about the wine and formulate your own conclusions. Wine Folly states, “Wine tasting is a head game. Confidence and bold assertion can often make someone look like a pro.”


Join us for a Periscope wine tasting with local experts, curators, and myself on Wednesday, November 18 at 3 p.m. You’ll see some live wine tasting where we’ll talk about terroir and suggest some wine pairings for Thanksgiving. And to celebrate the International Year of Soils, join us for a film screening of the Symphony of the Soil at the Wortham Giant Screen Theatre Dec. 1 at 6 p.m.

HMNS changed the way I think about Earth, time, humanity, and natural history

After 90 days working at the Houston Museum of Natural Science, here’s the verdict:

I love it here!

Through research required to compose and edit posts for this blog, I have learned about voracious snails, shark extinction, dinosaur match-ups, efforts to clean up ocean plastic pollution, Houston’s flooding cycle, a mysterious society in south China, and the inspiration for the design of costumes for Star Wars.


Look at the size of that T. rex! My love for the Houston Museum of Natural Science began with an affinity for dinosaurs.

I’ve learned about many, many other things, as well, and I could feasibly list them all here (this is a blog, after all, and electrons aren’t lazy; they’ll happily burden themselves with whatever information you require of them), but the point of this blog is to excite our readers into visiting the museum, not bore them with lists.

Coming to the museum is a grand adventure, and it’s my privilege to be here every day, poking through our collection and peering into the the crevices of history, finding the holes in what humanity knows about itself and speculating about the answer. That’s what science is all about, after all. Learning more about what you already know. Discovering that you’ve got much more left to discover.


As a writer, I identify with the oldest forms of written language, like this tablet of heiroglyphs. You can even find a replica of the Rosetta Stone in our collection!

When I took this job, I was a fan of dinosaurs and Earth science. I could explain the basic process of how a star is born and how the different classes of rock are formed. Igneous, metamorphic, sedimentary. Now, I can tell you which dinosaurs lived in what era and the methods paleontologists use to unearth a fossilized skeleton. I know that a deep-space telescope owes its clarity to a mirror rather than a lens, and I can identify rhodochrosite (a beautiful word as well as a fascinating mineral) in its many forms. And there are quite a few.


Rhodochrosite. My favorite mineral. Look at that deep ruby that appears to glow from within, and it takes many other shapes.

I have pitted the age of the Earth against the age of meteorites that have fallen through its atmosphere and have been humbled. The oldest things in our collection existed before our planet! How incredible to be that close to something that was flying around in space, on its own adventure across the cosmos, while Earth was still a ball of magma congealing in the vacuum of space.

Time is as infinite as the universe, and being in this museum every day reminds me of the utter ephemeralness of human life. It advises not to waste a moment, and to learn from the wisdom of rock about the things we will never touch. Time and space reduce humanity to a tiny thing, but not insignificant. Our species is small and weak, but we are intelligent and industrious. We have learned about things we don’t understand from the things we do. The answers are out there if you know where to look for them.


Everything turns to stone eventually, even this gorgeous fossilized coral.

I was a print journalist for three years, and I am studying to become a professional writer of fiction at Vermont College of Fine Arts. (Don’t worry. It’s a low-residency program. I’m not going anywhere.) I am a creator of records of the human experience, according to those two occupations, and in some ways I still feel that as the editor of this blog, but there is a difference.


This epic battle between a sperm whale and a giant squid recalls scenes out of Herman Melville.

Here, rather than individual histories — the story of one person or of a family or of a hero and a villain — I’m recording our collective experience, our history as a significant species that participates, for better or worse, in forming the shape of this world. We were born, we taught ourselves to use tools, we erected great civilizations, we fought against one another, we died, those civilizations fell. We have traced our past through fossils and layers of rock and ice, we have tested the world around us, and we have made up our minds about where we fit into the mix.

We are a fascinating and beautiful people, and through science, we can discover our stories buried in the ground, often just beneath our feet. To me, this is the real mission of our museum. To tell the story of Earth, yes, but to tell it in terms of humanity. In the Cullen Hall of Gems and Minerals, we wonder what makes certain minerals precious to us when they’re all spectacular. In the Morian Hall of Paleontology, we trace the fossil record back in time and wonder how things were and could have been had dinosaurs not gone extinct. In the Cockrell Butterfly Center, we connect with the little lives of insects, compare them to our own, and fall in love with our ecosystem all over again. In the Weiss Energy Hall, we learn how life and death create the fossil fuels that now power our society. We find both ingenuity and folly in the values of old civilizations in the Hall of Ancient Egypt and the John P. McGovern Hall of the Americas.


These chrysalises, a powerful symbol of personal growth and change, teach a lesson in natural cycles and big beauty in tiny places.

I have often wondered how we justify placing a collection of anthropological and archaeological artifacts under the heading “natural science.” Why don’t we consider our institution more representative of “natural history?” In my first 90 days, I think I’ve found the answer. It’s not just about the story of humanity; it’s about the story of the science we have used to learn what we know.


The Houston Museum of Natural Science, including the Cockrell Butterfly Center, is truly one of a kind.

Our goal at HMNS is to inform and educate. To challenge your assumptions with evidence and bring the worlds and minds of scientists to students and the general public. It’s a grand endeavor, one that can enrich our society and improve it if we pay attention.

A ticket to the museum isn’t just a tour through marvels, it’s a glance in pieces at the story of becoming human. After 90 days here, by sifting through the past, I feel more involved in the creation of our future than I have ever been.

And that feels pretty great.

Ice cream science: Make a cool treat to beat the summer heat

It’s getting to that time of year when it’s so hot and yucky outside that everything cold is better.

It’s also a time for telling kids about how, when you were their age, if you wanted ice cream you had to turn a crank until your arms fell off (presumably while walking uphill to school both ways and fighting off bears…).


Here in the Houston Museum of Natural Science education department, we have tried making ice cream in a variety of ways to see what is easiest for kids, and not all ways are equal. (Pro tip: Those special ice cream-making balls they sell for kids freeze shut, and then kids are sad. Not recommended.) Our favorite way, at the end of this post, is fairly cheap and easy and fun for kids, but before we get to the instructions, let’s talk about some science.

To make ice cream, you will of course need ice. The ice is simply to lower the temperature of the cream to the freezing point, but if you just used ice alone and let it sit, you’d end up with a solid block of cream – more like an ice cube – and it would take longer to freeze. What makes ice cream special is salt and stirring.


Water freezes at 32° F, but sprinkling salt on the ice lowers the freezing/melting point of water. How, you say? In order for liquid water to freeze to solid ice, all of the water molecules have to slow down enough to connect to each other and form solid crystals. When this happens, the water loses kinetic energy due to the decrease in movement of those molecules. Because temperature is a measurement of kinetic energy, this results in a lower temperature.

The presence of salt interferes with this process. The water molecules can’t attract each other as easily because they are also attracted to the sodium and chloride ions from the salt. Mixing the salt, ice, and water together results in a temperature below the freezing point of water, which helps the cream freeze faster. The shaking or stirring helps cool the cream evenly and efficiently. In ice cream, this lower freezing point turns the fats into solids, but the water content to be almost frozen.


What about the milk, then? It is much easier to make ice cream with creamer, heavy whipping cream, or half-and-half than to use skim milk because of the higher fat content in cream. You can make ice cream with skim milk, but it is really, really, really hard to do by hand, AND you have already committed to making ice cream, so I feel like you have acknowledged the inherent risk of fat consumption that comes with making a frozen confectionery delight. Just use the full-fat stuff, and let’s all move on.

What does the fat do, anyway? Primarily the higher fat content allows for a richer, creamier texture and a more delicious flavor in your finished product. The reason for this is that when you are cooling and mixing the cream, you are also introducing air molecules to the liquid. The bits of fat in the cream add a little structure to the ice cream and trap these air molecules in the solution as it forms. This, plus the lower freezing temperature, enables you to be able to scoop the ice cream fairly easily because it allows for there to be a bit of unfrozen water in the ice cream, which stops the ice cream from becoming a solid block of ice.


If you have ever had ice cream that has grown ice crystals and gotten a bit of freezer burn, those ice crystals appeared because the unfrozen water in the ice cream had a chance to migrate a little bit when the ice cream was warmed slightly on the ride home or when it was left on a counter a little too long and then frozen again. There are things called stabilizers added to your ice cream to prevent this from happening. Most ice creams today have one of five stabilizers added to them: carob bean gum* (a type of bean from Africa), carrageenan (a type of algae), guar gum (a type of legume from India), sodium alginate (made from seaweed) or carboxymethyl cellulose (sounds scary but it’s plant-based). Often, if you read the label, you will see more than one of these in your ice cream to keep it smooth and delicious.


* Carob beans, or locust beans, are cool. They are from exotic African trees and each bean is so similar that at one point they were used as a unit of measurement for gold and silver. We still use this measurement today, but the name has changed over time to Karat.

So now that you have had a little lecture about the science of ice cream, let’s get to the delicious lab work.


Activity: ICE CREAM!!!!


Individual serving containers of coffee creamer


Small waterproof container or quality sealable plastic sack big enough for about two or three cups of chipped ice

Salt, any variety

A dish towel to insulate your hands

Optional: Inexhaustible energy of small child-based labor



  1. Find some liquid coffee creamers in individual pots.
  2. Put ice in your water proof container, filling it about a third of the way. Smaller chunks of ice work better because there is more surface area, but any ice will do.
  3. Layer your salt on your ice. Several solid sprinkles will do, but if you are nervous about the quantity, add some extra just in case. It won’t hurt anything.
  4. Put your sealed creamer cup(s) in your container and then put more ice in, filling it about 2/3 of the way.
  5. Layer on more salt.
  6. Finish filling the container with ice.
  7. Start shaking your container. Make sure it is well sealed and that you have a firm grip on it. No one wants to be injured in an ice cream-related accident. There is no way to spin that so it sounds cool. Also, this is an excellent job for kids to help with. Put on a nice, long song or two and let them wiggle till they drop. About ten minutes will do it, but you will know when you are getting close because a frost will form on the outside of your container. If you don’t feel frost forming after a couple of minutes, add more salt. To speed this process up, start with creamer pods that have been stored in the fridge. This way, your creamer will start at about 50° F, and you won’t have to work so hard.
  8. After about 10 minutes of shake, shake, shaking your ice cream, dig your creamer cup out of the ice and wipe it off.
  9. Ta dah! You are done. Unless you want to make this tablespoon of delicious homemade ice cream into a sundae and add chocolate and banana or some jelly for more flavor.


Note: If you are thinking to yourself, “That seems like a lot of work for a tablespoon of ice cream,” well… it is. But it’s also science. So there.

If you get the liquid creamer that comes in a larger container at the grocery store, you can increase the volume of your creamer and make MORE ice cream. If you choose to do this, you will need to find a small waterproof (and I would suggest plastic) container to pour the creamer into and then a slightly larger waterproof container for all the ice and the salt. It’s the same procedure, just with a larger amount of the ingredients!