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Mixing Your Own Marshmallows: Finding the Right Ratio of Sugar to Corn Syrup

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Whether you are sitting around a campfire, or drinking hot chocolate after a day in the snow, nothing says fun quite like a marshmallow! Even its name is soft and spongy! In this cooking and food science fair project, you will make your own marshmallows several different ways, and discover the three special ingredients that give marshmallows their unique texture. You will also find out why they melt so quickly. Explore the science of these sticky, spongy sweets!


Areas of Science
Time Required
Short (2-5 days)
Material Availability
Readily available
Very Low (under $20)
Be careful when heating syrup in the saucepan. Adult supervision is required.

Kristin Strong, Science Buddies

Teisha Rowland, PhD, Science Buddies


Determine the ratio of sugar to corn syrup that produces the best-tasting and best-textured marshmallow.


What is your favorite way to eat a marshmallow? Melted in hot chocolate after a long day of sledding? Or roasted and squished between a slab of chocolate and graham crackers while you are sitting around a campfire? However you like them, marshmallows are an unusual type of sweet treat—spongy, sticky, and a little bit chewy, with a melting point that is just a bit above body temperature, so that they start to change from a solid to more liquid state as soon as they reach the warmth of your mouth, or the warmth of your hot chocolate or campfire! They are also an ancient creation, originally coming from a tall marshmallow plant (Althaea officinalis) that grows in swampy fields and has a soft, spongy root. The root contains mucilage, a thick, gluey substance produced by some plants and microscopic animals to help with water and food storage, and seed germination. Some cultures used the marshmallow plant to make candy, while others used it to make medicine. The ancient Egyptians, for example, dried the root and mixed it with honey to make marshmallow treats, but the early French thought the root looked like lung tissue, and experimented with making medicine out of its gummy juice to soothe sore throats.

A s'more

Figure 1. This photo shows a yummy marshmallow treat (called a s'more). (Larry D. Moore, 2006.)

Today's modern marshmallows contain no parts of the marshmallow plant though, because the plant is considered a medicinal herb. Instead, modern marshmallows are primarily a mix of three ingredients: sugar, corn syrup, and gelatin, with the gelatin replacing the thick, gluey substance from the marshmallow plant. The sugar and corn syrup are heated together with a little water to make a solution. The solution is warmed and brought to a boil, turning it into syrup. Because of the sugar in the solution, the boiling point of the solution becomes higher than the boiling point of pure liquid water (212°F). The greater the concentration of sugar in a solution, the higher its boiling point. As the solution boils, water evaporates, and the solution becomes even more concentrated with sugar, and the boiling point gets pushed even higher. For example, an 85 percent sugar solution has a boiling point about 28°F higher than the boiling point of pure water.

The final concentration of sugar in the syrup determines the structure of the candy that forms when the syrup cools. Think about the difference between the texture of caramels and lollipops—the caramel is softer and chewier, while the lollipop is hard and cracks when it is bitten. The syrup used to make caramels is cooked until it reaches 240–250°F, at which point it has an 87 percent concentration of sugar in solution and enters the firm ball stage (see the Exploratorium link in the Bibliography for more information about this). The syrup used to make lollipops, though, is cooked until it reaches a 99 percent concentration of sugar in solution (at a temperature of 300–310°F), which makes drops of the syrup turn into hard, brittle, easy-to-break threads when placed in cold water. When making marshmallows, the syrup is cooked until it reaches 235–240°F, or 85 percent concentration of sugar in solution, and corn syrup is added to the solution to help prevent crystals from forming in the cooled syrup. Nobody likes crunchy marshmallows!

So, where does the gelatin come in, and just what is gelatin anyway? Gelatin is that wiggly, jiggly food that seems almost magical as it suspends fruits, forms shapes and sculptures, and transforms from a solid to a liquid as soon as it hits the warmth of your mouth. It is not magic, but special gelatin molecules are responsible for these food tricks. Gelatin comes from collagen, the main protein in connective tissue, which is a specialized, fibrous tissue in animals that connects other tissues together, like tendons connect muscles to bone. The special quality of gelatin is that it is a protein that can coagulate (or come together) when it is beaten or whipped. So, to make marshmallows, hot concentrated syrup is beaten into gelatin with a mixer. The beating process forms bubbles in the syrup and protein mixture, and the gelatin coagulates at the point where the air in the bubble and the syrup-protein mixture meet, stabilizing the bubble walls so they don't collapse.

In this cooking and food science fair project, you will make your own gooey marshmallows, using different amounts of sugar and corn syrup to find out which ratio of sugar to corn syrup, makes the best-tasting and best-textured treat.

Terms and Concepts



Materials and Equipment

Experimental Procedure

Preparing to Cook

  1. Wash your hands.
  2. Get out all cooking tools and ingredients, and set them out so they are ready to go and easy to access.
  3. Identify the 240°F mark (116°C) on your candy thermometer. This is the traditional temperature used to make marshmallows.

Preparing Your Cake Pans

  1. Label the bottoms of three cake pans with masking tape pieces, numbered from 1 to 3. Pan 1 will contain recipe 1, pan 2 will contain recipe 2, and pan 3 will contain recipe 3. Each recipe contains a different ratio of sugar to corn syrup.
  2. Pour a small amount of vegetable oil on a paper towel and lightly oil the three cake pans.
  3. Pour a small amount of powdered (confectioner's) sugar in the strainer and dust the inside of the cake pans.
    1. If you get too much powdered sugar in the pan, hold the pan upside-down over a sink, and gently tap out the excess.

Preparing Your Gelatin

  1. Pour 1/6 cup of cold water into the large mixing bowl
    1. To get 1/6 cup, just fill the 1/3 measuring cup up halfway with water.
  2. Sprinkle one ¼-ounce (oz) envelope of plain, unflavored gelatin over the cold water.
  3. Mix the gelatin and water together for about 5 seconds (sec.) with a fork and set the bowl aside. This will give the gelatin time to "soften" or "bloom," as shown in Figure 2 below.

Gelatin with small bubbles

Figure 2. This photo shows the gelatin "blooming" in a small amount of water.

Preparing Your Syrup

  1. Add ¼ cup of cold water to the saucepan.
  2. Using Table 1 below as a guide, add granulated sugar and corn syrup to the water in the saucepan, according to which recipe you are currently making. This step is shown in Figure 3 below.

Ingredients Recipe 1 Recipe 2 Recipe 3
Sugar 1/2 cup 2/3 cup 3/4 cup
Corn syrup 1/3 cup 1/4 cup 1/6 cup
Ratio of sugar to corn syrup 1/2:1/3 2/3:1/4 3/4:1/6
Ratio, written as a decimal 1.5 2.7 4.5

Table 1. To the saucepan, add the amount of sugar and corn syrup shown in this table based on the recipe you are currently making.

Small saucepan containing water, sugar, and corn syrup

Figure 3. This photo shows the small saucepan containing water, sugar, and corn syrup, ready to be warmed on the stove to form a syrup.

  1. Put the lid on the saucepan. An adult should closely supervise all work from this point on.
  2. Turn on the stove to medium-high heat.
  3. Lift the lid and check the solution in the saucepan about every 30 sec. until it just comes to a boil.
  4. Remove the lid and set it aside.
  5. Begin to measure the temperature of the syrup in the saucepan using the candy thermometer.
    1. When using the thermometer, do not let the tip of the thermometer touch the bottom or sides of the pan. Instead, try to put the tip below the surface, closer to the middle of the pan.
  6. Continue heating your syrup solution until the temperature reaches 240°F (116°C).
    1. WARNING: The syrup will be very hot, so use extreme caution when working around the pan.
    2. Observe how the temperature rises. Does it go up quickly at first? What happens as the solution becomes more concentrated? Record your observations in your lab notebook.
  7. When the temperature reaches 240°F (116°C), immediately turn off the stove and move to the next section, Making Your Marshmallows.

Making Your Marshmallows

  1. Turn the mixer on low, and carefully pour the hot syrup solution into the gelatin and water in the large mixing bowl, as shown in Figure 4 below.
    1. Note: Some syrup solution will likely solidify on the saucepan as the syrup cools. However, if you pour too slowly, or wait too long and do not immediately pour the syrup into the bowl after turning off the stove, you may end up with a lot of syrup solidified on the saucepan, which may affect your results.

Contents of a pot whisked into gelatin

Figure 4. This photo shows the hot syrup slowly being poured into the gelatin while the mixer is operating on low.

  1. Set the timer for 11 minutes and start it.
  2. Gradually increase the speed of the mixer until it is operating at full (high) speed, as shown in Figure 5 below.

Bubbles forming while gelatin is mixed at high speeds

Figure 5. This photo shows how the mixture will look as you begin to operate the mixer at high speed.

  1. Continue to beat for approximately 11 minutes, or until the mixture starts to become very thick, glossy, and lukewarm.
  2. Add ½ teaspoon of vanilla, as shown in Figure 6 below, and beat for another minute.
    1. Write down the total time that you beat the recipe in your lab notebook.
    2. Try to beat each recipe for approximately the same amount of time.

Foamy gelatin mixture

Figure 6. This photo gives an example of how the mixture will look at the end of 11 minutes after you have added the vanilla, and before you beat for the final minute.

  1. Pour a thin layer of vegetable oil on a spatula and scoop out the marshmallow mixture from the mixing bowl and into the prepared cake pan with the masking tape piece that matches the recipe number.
  2. Use the spatula to gently smooth down the top of the marshmallow, so that it is pretty flat.
    1. If the top of the marshmallow mixture naturally smoothes itself down when you put it in the pan, or if the mixture is so sticky that it is very difficult to smooth it down with the oiled spatula, skip this step.
  3. Wash and dry all cooking utensils.
  4. Repeat the sections Preparing Your Gelatin, Preparing Your Syrup, and Making Your Marshmallows two more times with clean materials, until all three recipes have been prepared, as shown in Figure 7 below.
    1. To have the best controll over all the variables you should make all three recipes on the same day. Otherwise, uncontrollable variables (like the humidity on that day) may affect your results.
  5. Repeat the entire Experimental Procedure (up to this point) two more times so that you have a total of three trials (pans) for each recipe. Repeating the recipes makes sure that your test results are accurate and repeatable.
    1. You can do this step on a different day if you would like.

Three pies covered in marshmallow spread

Figure 7. This photo shows the three finished recipes cooling and becoming more firm.

  1. Allow the three marshmallow "pies" to sit out, uncovered, on a counter for at least 4 hours, or up to overnight, so that they can become firm.

Preparing Your Marshmallows for Testing

  1. Once the marshmallow pies have become firm, after at least 4 hours or overnight, turn the pans over, one at a time, onto a cutting board.
    1. If the marshmallow sticks to the bottom of the pan, push on the bottom of the pan a bit, or use a spatula to help lift it out.
  2. Roll a pizza cutter in some powdered sugar, and then use it to cut up your marshmallow into pieces that are about 3 centimeters (cm) by 3 cm. Use a ruler to help measure where to cut.
    1. An alternative to the pizza wheel is to use a small cookie cutter to cut out shapes.
  3. Dust the marshmallows on all sides with a little powdered sugar, using the strainer.
  4. Place the marshmallows in the air-tight container or plastic bag, being sure to label the container or bag with the recipe number and the trial number (remember, you will be performing three trials) from the masking tape pieces, so that you know which recipe was used for each bag or container. The marshmallows will keep in an airtight container for up to a week, so you have around six days in which to make and test all the trials.

Testing Your Marshmallows

Perform the following three tests to investigate the melting temperature, the toughness, and the taste of the marshmallows you made from each recipe. Perform each test one trial set at a time.

  1. Melting tests: Drop three marshmallow pieces (one from each recipe) in a pan of hot water and see which piece melts first.
    1. Because of slight variations in marshmallow sizes, pick three pieces that are of the same size and shape.
    2. Start a timer and see which one melts first, second, and last. Record your results in a data table in your lab notebook.
    3. Repeat the test at least three times per trial set to make sure your results are repeatable and accurate.
  2. Cutting tests: See which marshmallow is the toughest using a cheese cutter, like the test described in the Science Buddies cooking and food science fair Project Idea Tough Beans (in the Procedure section titled "Testing Your Cooked Beans"). Alternatively, you can try an easier but less quantitative method using a small disposable cup, like a Dixie cup.
    1. If you use the disposable cup method, do the following:
      1. Put a marshmallow piece from one of the recipes on a cutting board.
      2. Arrange a small cookie cutter so that it can sit on top of the marshmallow. (You will need the cookie cutter to be thinner than the marshmallow pieces to do this.)
      3. On top of the cookie cutter, balance the small disposable cup.
      4. Put 20 pennies in the cup, one at a time.
      5. Remove the cup and cookie cutter from the marshmallow piece and inspect the marshmallow. Did the cookie cutter leave a noticeable impression? Use a camera to take a picture of the marshmallow piece.
      6. Repeat this process with marshmallow pieces from the other recipes. Eventually you will want to have repeated the test at least three times per trial set. Record your results in a data table in your lab notebook.
  3. Taste tests: Gather your family and friends and give them three samples of marshmallows, one from each recipe in a trial set. Have them evaluate the samples for taste and texture.
    1. Which recipe do they think made the best-tasting samples? Which recipe do they think made the best-textured samples? Record your results in a data table in your lab notebook.
    2. Read this Science Buddies article about sample size to determine how many volunteers you will need.

Analyzing Your Results

  1. For melting tests, average the results of your time tests from the three trials, and plot the decimal ratio of sugar to corn syrup on the x-axis, and the melting time on the y-axis.
    1. Do you see a correlation between the melting time and the ratio of sugar to corn syrup used? If so, why do you think this is? Hint: Re-read the Introduction.
  2. For cutting tests, if you used the protocol from the science project Tough Beans, average your coin counts from the three trials (to get a measure of the force required to cut through the marshmallow), and plot the decimal ratio of sugar to corn syrup on the x-axis, and coin counts (or cutting force) on the y-axis.
    1. If you used the small disposable cup method, print out the pictures you took and put them on your science project display board.
    2. Do you see a correlation between how tough the marshmallow pieces were and the ratio of sugar to corn syrup used? If so, why do you think this is?
  3. For taste tests, make a bar chart showing the ratio of sugar to corn syrup on the x-axis, and the number of people who thought it had the best taste on the y-axis. Make a second bar chart showing the decimal ratio of sugar to corn syrup on the x-axis, and the number of people who thought it had the best texture on the y-axis.
    1. Why do you think some people preferred marshmallows made using one recipe compared to marshmallows made using another recipe? Were some pieces too sweet or too hard for your taste testers, or not sweet enough or too soft?
icon scientific method

Ask an Expert

Do you have specific questions about your science project? Our team of volunteer scientists can help. Our Experts won't do the work for you, but they will make suggestions, offer guidance, and help you troubleshoot.


  • Develop other ways to test your marshmallows. For example, measure the density of the marshmallows from each recipe, using a scale, graduated cylinder, and Archimedes' principle. Plot the ratio of the sugar to corn syrup on the x-axis and the density on the y-axis.
  • Choose the recipe that has a decimal ratio of 2.7 for the sugar to corn syrup. Vary the final cooking temperature (deviate from the traditional 240°F) to see how that affects the taste, texture, melting time, toughness, and/or density. Be sure to conduct repeat trials at each temperature you test.
  • Break up your taste-testing volunteers into male and female, or by age, to see if there are gender or age differences in marshmallow taste or texture preferences.


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MLA Style

Science Buddies Staff. "Mixing Your Own Marshmallows: Finding the Right Ratio of Sugar to Corn Syrup." Science Buddies, 20 Nov. 2020, https://www.sciencebuddies.org/science-fair-projects/project-ideas/FoodSci_p065/cooking-food-science/making-marshmallows?from=Blog. Accessed 2 Dec. 2023.

APA Style

Science Buddies Staff. (2020, November 20). Mixing Your Own Marshmallows: Finding the Right Ratio of Sugar to Corn Syrup. Retrieved from https://www.sciencebuddies.org/science-fair-projects/project-ideas/FoodSci_p065/cooking-food-science/making-marshmallows?from=Blog

Last edit date: 2020-11-20
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