Hands-on engineering challenges can provide engineering activities for kids, but sometimes it’s harder to teach circuits and electrical engineering for kids as part of creative STEM activities for kids.
But with this rainbow salt circuit engineering activity, kids will have a blast learning about how electricity works!
Keep reading to learn how to make a rainbow salt circuit!
How to Make a Rainbow Salt Circuit
Follow along with these directions to learn how to power a circuit using salt and water!
But first, learn a bit about how salt circuits work and what supplies you’ll need for this rainbow STEM activity!
You’ll also want to check out these other rainbow STEM activities for kids.
How a Salt Water Circuit Works
Salt and water are conductive for electricity.
The water inside the glue helps carry the electrical charge from the battery pack along the salt path.
This current travels from salt molecule to salt molecule, but it needs the water to be successful. Dry salt won’t carry the current effectively.
The fun watercolors help keep the glue and salt wet enough, and it is fun to watch the colors spread and mix in the salt lines as well!
The wetter your salt line (as long as you don’t completely dissolve it), the better your current will travel and the more easily you will get your light to shine.
Salt Circuit Engineering Tips
This project can be a bit frustrating because things have to be *just* so to make it work.
The positive side of the LED light has to connect to the positive side of the salt circuit. The long end of the LED wire and the red side of the battery pack must be connected.
If things aren’t held in place securely, the LED light cannot turn on. You may have to spend a few minutes adjusting the placement of the battery pack paddles and the LED wires to get things working.
Adding a bit more liquid watercolors to the salt line if it gets dry will also help.
If it’s bright where you are and you are not sure if the LED light is shining, you can connect something that will make a sound instead, like we did in our demonstration video.
What You Need to Make a Rainbow Salt Circuit
For this salt circuit project you will need:
We also like to keep these STEM supplies on hand:
The Mason Jar Scientist: 30 Jarring STEAM-Based ProjectsBall Regular Mouth Mason Jars with Lids and Bands, 16-Ounces (4-Pack)Crisco Pure Vegetable Oil, 32 OunceBarbasol Soothing Aloe Thick & Rich Shaving Cream 10 Oz (2 Pack)Alka-Seltzer PFY BXAS50 80659297 Antacid and Pain Relief Medicine, Two-Pack (Pack of 50)Kadaon 10X Handheld Magnifier Antique Mahogany Handle Magnifier Reading Magnifying Glass for Reading Book, Inspection, Coins, Insects, Rocks, Map, Crossword PuzzleBORAX 20 Mule Team Laundry Booster, Powder, 4 PoundsFine Ground Celtic Sea Salt – (1) 16 Ounce Resealable Bag of Nutritious, Classic Sea Salt, Great for Cooking, Baking, Pickling, Finishing and More, Pantry-Friendly, Gluten-FreeMcCormick Assorted Food Color, 1 Fl Oz (Pack of 1)Food Coloring – 12 Color Vibrant Cake Food Coloring Set for Baking, Decorating, Fondant and Cooking – Upgraded Liquid Concentrated Icing Food Color Dye for Slime Making, DIY Crafts – .25 fl. oz. Each30% Pure Vinegar – Home&Garden (1 Gallon)Arm & Hammer Pure Baking Soda, 5 lbArgo Corn Starch 16 oz. Box (Pack of 4)
Find worksheets and the complete lesson plan for this project and a complete summer STEM program in the Summer STEAM Camp book!
How to Do the the Rainbow Salt Circuit Activity
Follow along with these instructions on how to make your own rainbow salt circuit to learn about electricity and currents in a kid-safe way!
You can also watch this video to see how we did our version.
First, lay out your two pieces of paper next to each other.
Plan where the battery pack will connect to the paper with play dough and where the LED light wires will connect through the glue path.
Mark these spots on your paper.
Spread the glue out in a curving path.
Add play dough dabs in the spot marked.
Sprinkle salt over the glue lines.
Use the pipette to pick up liquid watercolors and drop the color onto the salt lines. Use blue and yellow on one side and yellow and red on the other.
Where the colors meet, they will combine to make secondary colors and complete the rainbow.
Connect the long side of the LED light wire to the same circuit that is attached to the red paddle for the battery pack.
Connect the short wire and the black side on the other glue line.
Turn on the battery pack and watch the light glow!
If it doesn’t work, read the troubleshooting section below:
Salt Circuit Troubleshooting
If the light doesn’t come on, check the following things:
- Are the correct sides of the LED wires and battery pack aligned?
- Is the salt wet enough?
- Does the battery pack have batteries?
- Are the LED wires touching the salt?
- Is the playdough touching the glue lines?
- Are the paddles fully inserted into the play dough globs?
- Is the LED light burned out?
Addressing these issues should resolve any problems you have with this salt circuit project.