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Make String from Algae

20 reviews


Active Time
2-3 hours
Total Project Time
3 or more days
Key Concepts
Polymers, chemical reactions, biomaterials, fiber arts


Did you know that the seaweed you've seen in the ocean or even eaten as a snack is inspiring innovators to imagine new materials? Large brown algae, like kelp, contains polymers—long chains of molecules—that are more environmentally friendly than the ones in most plastics. These natural polymers (alginates) could eventually be used to create sustainable everyday objects. Try your hand at using a bit of chemistry to turn biodegradable polymers from algae into your own custom string! Educators, a lesson plan is also available for this topic.

This activity is not recommended for use as a science fair project. Good science fair projects have a stronger focus on controlling variables, taking accurate measurements, and analyzing data. To find a science fair project that is just right for you, browse our library of over 1,200 Science Fair Project Ideas or use the Topic Selection Wizard to get a personalized project recommendation.

Design Challenge

Make your own colorful string using polymers that come from algae. Then craft fun creations with your algae string!


You will need two special ingredients, sodium alginate (algae polymer) and calcium chloride. These are the chemistry superstars that react together to form a new material! You'll also need some basic kitchen equipment and supplies to customize your string. We have included our favorite suggestions below to get you started, but use whatever you have on hand—be creative!

Science Buddies' Spherification Kit contains the sodium alginate and calcium chloride needed to do this experiment. The Tech is not associated with Science Buddies' kits.

Do not eat the resulting algae string; this activity was not designed with consumption in mind.
Table listing categories and details of Gel Preparation supplies

To prepare the gel, you will need the following items. One mixing container such as a squeezable bottole, jar, cup, plastic baggie, bowl, or food storage container, A teaspoon of sodium alginate; found online, or at specialty grocery stores and pharmacies. One-half cup of water; bottled or filtered tap water is strongly recommended, if you have it. One to three tablespoons of a texture ingredient like honey, corn syrup, pancake syrup, aloe vera, or vegetable glycerin. Up to one teaspoon of a color ingredient like food coloring, powdered drink mix, natural pigments like tumeric, or juice from fruits and vegetables like red cabbage or berries.

Note: Some Mixing Containers will need a utensil to stir. Some can double as a Dispensing Tool. (View a larger version of the Gel Preparation Supplies.)

Table listing categories and details for String Making Supplies

To make the string, you will need the following items. One bath container such as a bowl, food storage container, pan, or baking dish. Two cups of water; any type, including tap water, will work. Two teaspoons of calcium chloride; found online or at brewing supply stores. One or more dispensing tools such as a squeezable bottle, jar or cup, plastic baggie, piping bag, or a syringe without a needle.

Note: Bath Container should be large enough to reach into and make a bath that is at least one inch deep. (View a larger version of the String Making Supplies.)

  • Why filtered water? Many homes have hard water, which has minerals like calcium. Since calcium is used in the chemical reaction, your algae gel could solidify too soon!
  • Why texture ingredients? These sticky substances help keep your string from becoming stiff and breakable.
  • Why a dispensing tool? This handy tool will help you shape your gel before you transform it into a solid string. Remember some mixing containers can also be used as dispensers.


Prepare gel 1 hr-1 day
Make string 30 min
Create 30 min-4 hours

Part 1: Prepare your algae gel (1 hr-1 day)

The basis of your string will be algae gel, a gooey combination of ingredients you mix to your own specifications. Watch how your adjustments to the color and texture affect your string later!

  1. Choose the texture and color ingredient(s) you want to use to customize your algae string. Add them to a mixing container with water and mix to combine.

    1/2 cup Water (filtered or bottled recommended)
    1-3 tbsp Texture Ingredient(s) (honey, etc.)
    Up to 1 tsp Color Ingredient(s) (food coloring, etc.)

    Tip: Make more batches to experiment with different combinations or multiple ingredients!

  2. Add in the sodium alginate powder. Mix until a thick gel begins to form (about 5 min).

    1 tsp Sodium Alginate Powder
  3. Your algae gel will be ready to use when there are no more powder clumps.

    Excited to make string right away? Mix by hand. Tired of mixing? Let it sit overnight.
    • Continue to actively mix your gel until all clumps have broken up and dissolved.
    • This will take some effort and time (30 min or more), but can be a fun challenge!
    • The air bubbles trapped in your gel won't have time to escape, which may weaken your string.
    • Clumps will finish dissolving by themselves as your gel rests.
    • Seal or cover your container to stop your gel from drying out while it sits.
    • This extra time also allows air bubbles to escape, which can strengthen your string.
Learn More
  • Video: What's the Chemistry?  Zoom in for a peek at the chemistry that turns your gel into a solid string.
  • Algae String Essential Questions Such as... will this clog my sink?

Part 2: Make your algae string (30 min)

It's time to use chemistry to change your gooey gel into a solid string. The chemical reaction will start when the alginate in your algae gel meets the calcium in your calcium bath.

  1. Combine water and calcium chloride in your bath container and mix to make the calcium bath. (You can reuse your bath for several batches of string.)

    2 cups Water (any type)
    2 tsp Calcium Chloride
  2. Transfer your algae gel into a dispensing tool of your choice.
  3. Use your dispensing tool to add your algae gel to the calcium bath.
    • Depending on the tool used, pour your gel from above or push it through a small opening, like squeezing toothpaste from a tube!
    • To avoid clogs, keep your dispensing tool from touching the bath.
    Piping Tube squeezes algae gel into cup of liquid labeled calcium bath
  4. Let your string sit in the calcium bath for a few minutes before removing.
    • Give it a test squeeze. If it isn't as solid as you want, put it back in to soak longer.
Activity Tips
  • Video: How Dried String Changes:  Fresh string is squishy—what happens as it dries?
  • Algae String Tool Chest Learn how tools affect your gel and string.

Part 3: Create some custom algae string creations! (30 min-4 hours)

See what you can make with your algae string! Can you tie it into a bow? Or use knots to make a bracelet? Try using it to knit or weave an awesome creation!

Series of three images, crocheting with algae string, key chain lanyard tied with algae string, red and white algae string bracelet
Like your wet string? Start creating! Want something more stable? Let your string dry.
  • Use it to make fun creations, but proceed with caution: Fresh string is fragile!
  • Your creations will change as the string dries out.
  • Drying can take a few hours or more, but stretching out your strings and using a fan can speed things up.
  • Dried string creations stay the same for months!

Note: You can dispose of leftover algae gel and unwanted string in the trash. Pour your calcium bath down the drain.

Explore More

  • Customize! Make multiple batches of string that are different colors, shapes, or thicknesses. How about a more stiff or flexible string?
  • All strung out? Make a 2D creation! Trace your algae gel into a pattern on a plate, then gently pour your calcium bath around it until it's completely covered. What other creations can you make?
  • New tools. Use materials from around your house to build a new type of dispensing tool. What kind of string does it make?
Get Inspired!

Additional Resources

 SEPA (Science Education Partnership Award) Logo
This activity was developed by The Tech Interactive with funding from a Science Education Partnership Award (SEPA) from the National Institute of General Medical Sciences (NIGMS) at the National Institutes of Health (NIH).
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