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One free scan finds every outdated or missing driver and matches the right update for your exact hardware.Free scan · exact hardware matchYou can make a working cipher wheel, reveal a lemon-juice message, or build a periscope with ordinary craft materials. These seven spy-inspired projects focus on codes, optics, signaling, and creative play—not covert surveillance. Most use supplies you may already have; thermochromic paint is the specialty material in the group.
Choose a project by what you want to explore
| Project | What it explores | Key materials | Reuse |
|---|---|---|---|
| Cipher wheel | Letter substitution and code keys | Paper or cardstock, scissors, pencil or paper clip | Reusable; rotate the wheel to change the mapping |
| Invisible ink | Hidden writing and revealing methods | Paper, lemon juice, water, cotton swab or brush, lamp | Make a fresh message for each attempt |
| Periscope | Reflection and light paths | Carton or box, two small mirrors, paper, scissors, tape, marker | Reusable if kept intact |
| Chroma cipher | Temperature-sensitive color change | Thermochromic paint and a message template | Depends on the paint and template; the activity page does not state how many uses to expect |
| Spy alarm | Simple mechanisms and cause-and-effect | Use the materials specified in the Spy Museum activity | Not stated by the activity listing |
| Signaling device | Communication through signals | Use the materials specified in the Spy Museum worksheet | Not stated by the activity listing |
| Camera obscura | Light, image formation, and optics | Foil, baking paper or a cereal-box bag, cardboard tubes, scissors, sticky tape | Reusable if the construction stays intact |
The table describes project topics and materials reported by the linked institutions, not measured rankings of time or difficulty. The Spy Museum activity listings do not give complete material lists for the alarm and signaling projects, so check their instructions before gathering supplies.
1. Make a cipher wheel
A cipher wheel lets two people encode and decode messages using a shared letter key. KID Museum’s activity uses paper or cardstock, scissors, and a pencil or paper clip; cardboard or a paper-towel tube can be optional additions. Cut and assemble the wheel according to the activity, then agree with the recipient on a starting letter or key. Rotate the wheel to change the letter mapping, and make sure the receiver knows which key to use.
For a fresh puzzle, send the encoded message and the agreed key separately. Keep the code playful and use it for games rather than concealing anything that could put someone at risk. KID Museum’s Make It! Spy KIDS activities include the wheel and other spy-themed builds; the International Spy Museum also has code and decoder-wheel activities.
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2. Write an invisible-ink message
For the lemon-juice version demonstrated by PBS, gather paper, lemon juice, water, a cotton swab or brush, and a lamp. Write with the juice, let the paper dry, then warm it near a bulb until the writing appears. The demonstration uses a lamp; do not substitute a flame. Use adult supervision when warming paper, and keep it at a safe distance from the bulb.
Invisible ink can also introduce the idea that different materials reveal writing in different ways. The Spy Museum lists activities using heat, UV light, or other reactions, but follow the method and safety directions for the specific materials you choose. See PBS’s lemon-juice invisible-ink activity and the Spy Museum youth activities.
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3. Build a two-mirror periscope
A periscope is an optics project, not just a spy prop: two mirrors redirect light from the top opening down toward the eyepiece. MIT-hosted instructions list a carton or box, two small mirrors, paper, scissors, tape, and a marker. Cut openings as directed, place the mirrors at the specified angles, and secure them so the image from the top opening reflects toward the viewer. The exact cuts and positioning matter, so use the illustrated instructions rather than guessing.
The International Spy Museum also provides a template-based periscope activity. Compare its template with the MIT-hosted homemade periscope instructions before cutting; both approaches use mirrors to make an image visible from a different position.
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4. Try a color-changing chroma cipher
This project hides a message with thermochromic paint, which changes color when heated. The International Spy Museum describes a chroma cipher activity using that effect. Apply the paint to a message template as the activity directs, then use the specified warming method to reveal the hidden part. Because the source identifies thermochromic paint as the key material but does not specify a particular product or its handling limits, follow the paint’s own label and the activity’s safety instructions.
This is the one project here that depends on a specialty material rather than only basic household supplies. Find the activity through the International Spy Museum’s youth activities.
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5. Make a simple spy alarm
The Spy Museum’s educator resources include a spy-alarm build. Treat it as a hands-on demonstration of how a simple trigger can produce a signal, not as a security device to rely on. The activity listing does not specify a complete materials list, so open the museum’s instructions and check what they require before starting. Adapt the build only in ways that preserve the activity’s safety guidance.
See the Spy Museum educator activities for its alarm-related resource.
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6. Build a signaling device
A signaling activity offers a way to practice communicating with an agreed code rather than hiding or intercepting messages. The Spy Museum lists a signaling-device worksheet and a separate telegraph lesson built around a simple circuit and switch. Follow the worksheet for the device you choose; its activity listing does not provide a full materials list here.
Keep the exercise to a controlled game with a partner who knows what the signals mean. The museum’s signaling-device resources include the activity and telegraph lesson.
7. Make a camera obscura
A camera obscura is another way to explore optics with simple materials. The National Gallery of Ireland lists foil, baking paper or a cereal-box bag, cardboard tubes, scissors, and sticky tape for its activity. Follow its instructions to assemble the viewing device and observe how light forms an image. The University of Cambridge Museums describes its camera-obscura project as suitable for children aged six and older; adult help with scissors is sensible.
See the National Gallery of Ireland camera-obscura activity and the University of Cambridge Museums activity.
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Make a spy kit to keep the projects together
Turn a lunchbox, backpack, or cardboard container into a project kit with simple compartments. KID Museum suggests adding a homemade cipher wheel, notebook, pencils, sunglasses or a hat, and a magnifying glass. Label pockets for code-making, drawing, and supplies so the kit supports pretend missions without suggesting real surveillance.
Use the container to store the reusable wheel and periscope; keep the materials for single-use message experiments separate and follow their safety directions. KID Museum’s spy-kit activity offers a starting point for customizing the container.
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