Invisible Ink: A Citrus Painting Experiment

It’s summer and we’ve been doing a lot of citrus juicing in our home. Between my 4-year old expert juice squeezer and my almost 2-year old juice taster,  our simple and inexpensive juicer has been hard at work.

invisible ink science activity kids

While little Rainbow napped, Nutmeg and I gathered materials and set up the project. We talked about how we’d have to reveal the ink (lime juice) with the high heat of an iron or hair dryer, and she couldn’t wait to get started. She loves dangerous tools.

invisible ink citrus kids

We gathered our ingredients.

Here’s the full recipe:

Invisible Ink: A Citrus Painting Experiment


Prep time: 

Making time: 

Total time: 

Lemon juice is acidic, and acid weakens paper. When paper is heated, the acid burns and turns brown before the paper does.
  • Lemon or Lime Juice
  • Paper
  • Paint brush or Q-tip
  • Iron
  1. Squeeze lemon or lime into a bowl.
  2. Paint the juice onto your paper with a paint brush or Q-tip.
  3. Wait for the paper to dry.
  4. Heat the paper with an iron, hair dryer, light bulb, or other heat source. Be careful that you don't hold it there to long, as it could burn the paper.
Experiment with other liquids: milk, orange juice, white wine, vinegar, and apple juice are good bets.


invisible ink citrus lemon lime kids

Just as we were getting started, baby R woke up to join us. She’s 22 months old now, and enjoyed the sensory experience of squeezing the limes with her bare hands, and then licking her fingers. According to my mom I used to eat lemons right off our tree, so this wasn’t too much of a surprise.

invisible ink lemon lime juice

The girls experimented with different colored papers and brushes. Afterwards I realized that Q-tips would have been perfect for this project, but we enjoyed the challenge of small watercolor brushes.

invisible ink citrus lemon lime kids

The papers dried pretty quickly on this warm day and we were able to get right to the fun part of burning the acid with heat. N’s grandma blows her hair dry every day, and N is obsessed with this tool. Obsessed. We ran the heat on the paper for about a minute with little success. I never blow dry my hair and have a cheap blow dryer for projects like this, and maybe that’s why? In any case, we decided to move on to the iron.

invisible ink citrus lemon lime kids

I folded a thick towel, placed the art on top of it, and she ironed away. In most cases an ironing board would have been better, but ours pulls awkwardly out of the wall and it’s too tricky to get the three of us around it safely. This worked perfectly and only took a few seconds to show its results.

invisible ink citrus lemon lime kids

N’s picture of her and her dad (he’s above her head, slightly visible in all his heated lime acid glory).

invisible ink citrus lemon lime kids

I really like how the abstracted images turned out and wished I had joined them once I saw how cool these looked. I usually join in when we’re creating and somehow forgot to on this round.

How about you? Do you find yourself doing projects with your kids, or are you in more of the facilitator mode? And what do you think about the new recipe card tool and header?


  1. says

    This looks great Rachelle! I don’t have a printer at the moment, but I love to be able to print a clean recipe from the internet without advertisements and other miscellaneous text and images on the page. I usually print onto a standard sheet of paper and use the bottom portion for notes and use the recipe folded in half in the kitchen. I don’t have a recipe card holder or book, but an organization system idea to go with your recipes might be good. I’m a sucker for pictures too, so I love it when the recipe comes with one.

    • rachelle says

      Thanks for taking time to give me your thoughts, Amber. It’s helpful to hear how you use printed recipes. I usually add notes to mine as well, but not so thoughtfully! I like the idea of turning this into a whole system — you’re giving me lots to think about.

    • rachelle says

      Thanks Krissy. This is the first one I drafted as a recipe card, but I think I’ll go back and reformat some old posts, as well as use this going forward.

  2. says

    love the recipe card… what did you use to embed that??
    This looks like a super fun idea… when it comes to art activities I often get involved with my kids because I love mucking around with paint just as much as they do!

  3. danielle says

    You are a tinkerer and your header changes every once in a while and i love seeing what you’ve created and they are all fabulous. Keep tinkering.
    And i am definately going to do this project!!!!

    • rachelle says

      Thanks for saying that, dan 🙂 I often worry that I’m too impulsive and should just sit tight with something if it’s working. Simone will enjoy this one. Get the iron ready!

  4. Megan S. says

    Awesome! I was already going to do invisisible inks to start next years science classes (K-3) but I love the idea of trying different heating methods. I hadn’t thought of that. Thank you

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