I love little tricks that feel like small, domestic miracles: a message that appears and vanishes, an ink that fades like a ghost. Disappearing ink effects are perfect for that — they’re cheap, safe (when done sensibly) and wonderfully theatrical. In this piece I’ll show you how to make a disappearing ink using common household materials, explain the science behind it, and give ideas for playful projects you can try right away.
What is “disappearing ink” and how does it work?
At its simplest, disappearing ink is a liquid that leaves a visible mark that later becomes invisible or nearly invisible. There are a few different mechanisms for achieving this: chemical reactions that change the molecule’s colour, dilution of an indicator, or inks that become colourless when exposed to air, light or heat. The method I’ll walk you through uses a pH-sensitive dye (an indicator) combined with a mild acid or base so that the writing shows up and then fades as the pH shifts.
Why I like this method
I chose the pH indicator method because it’s:
- Safe: Ingredients are food-grade (vinegar, baking soda, lemon juice, commercial pH indicators like red cabbage extract) or household items.
- Accessible: You can source everything at the supermarket or reuse things from the kitchen.
- Playful: The timing can be controlled so the message fades slowly (perfect for a reveal) or quickly (a quick vanish).
Materials you’ll need
Here’s a simple shopping list. I often adapt quantities depending on how much writing I want to do.
- Red cabbage (or store-bought pH indicator like phenolphthalein — I prefer natural extracts)
- White vinegar (acetic acid) and/or lemon juice
- Baking soda (sodium bicarbonate)
- Water (filtered or tap is fine)
- Paper (plain printer paper works; you can experiment with heavier papers)
- Fine-tipped brush, pipette, or fountain pen (a dip pen or even a cotton bud works)
- Small saucepan, strainer, glass jars
- Optional: rubbing alcohol, eyedropper bottles for dispensing, pH strips for testing
Making the indicator: red cabbage extract
Red cabbage is a brilliant, dramatic indicator — it shifts through purple, blue, green and yellow depending on acidity. Here’s how I extract it:
- Chop roughly half a small red cabbage.
- Place the pieces in a saucepan, cover with boiling water and simmer for 10–15 minutes until the water deepens to a rich purple.
- Strain the liquid into a jar and let it cool. This is your indicator.
Tip: You can concentrate the colour by reducing gently over low heat, but don’t let it burn. I store leftover extract in the fridge for up to a week.
Preparing disappearing ink variations
There are two simple approaches you can try depending on whether you want the message to appear first and then disappear, or be invisible initially and become visible then vanish.
- Visible then fades: Mix cabbage extract with a small amount of baking soda solution (dissolve 1/4 tsp baking soda in 1 tablespoon water). The indicator turns bluish-green in alkaline. Use a fine brush or pen to write. Over time, exposure to air and carbon dioxide will neutralize the alkalinity and the colour will drift back toward purple and then pale, making the text fade.
- Invisible then appears briefly and disappears: Write with plain baking soda solution (invisible once dry). When you want the message to appear, brush or spray gently with cabbage extract — the baking soda makes the indicator change colour. The playful part is that if you then apply a little vinegar, the colour can shift again or become less visible as the pH changes your indicator’s hue.
Step-by-step basic recipe: write, reveal, vanish
This recipe gives a clear writing that fades within minutes to hours depending on conditions.
- Prepare a 1:4 mix of red cabbage extract to water. Add 1–2 drops of baking soda solution until the colour shifts toward teal/green.
- Load a fine brush or dip pen and write on paper. The mark should be visible immediately as a green-blue.
- Leave the paper exposed to air. Over time (from a few minutes to a couple hours) the colour will slowly return toward purple and then become much paler — your writing will “disappear”.
Control the timing by adjusting how alkaline you make the ink: stronger alkalinity tends to take longer to neutralise.
Tools and tweaks for better results
Small adjustments can make the effect more reliable:
- Paper choice: Smooth, less absorbent papers hold colour longer. Cartridge paper or Bristol board are nice. Very porous paper will make the ink vanish quicker.
- Concentration: More concentrated cabbage extract gives stronger colour; more baking soda increases alkalinity and persistence.
- Droppers and pens: Eyedropper bottles or refillable fountain pens give better control than cotton swabs.
- Sealing: If you want to delay fading, store the paper in an airtight bag. The carbon dioxide in air is what neutralises alkalinity over time, so limiting exposure preserves the colour.
Safety and practical notes
This is a low-risk project, but a few sensible precautions:
- Work on a protected surface to avoid staining fabrics or wood — cabbage extract can dye surfaces temporarily.
- Avoid ingestion of concentrated chemicals; food-grade ingredients like vinegar and baking soda are safe in small kitchen quantities but aren’t for tasting in this context.
- If you try store-bought indicators (like phenolphthalein), read the safety instructions — some lab indicators are not food-safe.
Troubleshooting
Here are issues I ran into early on and how I fixed them:
- Ink too faint: Use more concentrated cabbage extract or reduce water. Try a less absorbent paper.
- Disappears immediately: Your paper may be too porous or the environment too humid. Use thicker paper and increase alkalinity a touch.
- Colour shifts oddly: Indicators move through a range; take a few practice strokes to learn the palette. pH strips help if you want precise control.
Creative ways to use this trick
Once you have the basics, the possibilities feel endless. A few ideas from my sketchbook:
- Secret notes: a note that fades after being read makes for playful reminders or ephemeral messages to leave for friends.
- Interactive prints: print a faint pattern with baking soda solution and reveal with cabbage spray during a workshop demo.
- Story prompts: in a zine, reveal and hide clues as part of a mini mystery.
- Educational demos: this is a lovely way to teach kids about acids, bases and indicators — and about experimentation itself.
Variations to explore
Once you’re comfortable, try these experiments:
- Use turmeric (it reacts with bases and changes colour) for a warmer palette.
- Swap natural indicators for commercial ones: phenolphthalein gives dramatic pinks in base, while methyl orange offers bright shifts in acid.
- Combine with heat-sensitive or UV-reactive inks for layered magic.
This little trick is as much about process as it is about the final vanish. I find the best results come from playful tinkering: keep a notebook of ratios, papers and timings. If you try it, tell me what you made — and if a faded note sparks a tiny smile, then the experiment did its job.
