By Meredith Brustlin, CMNH Educator

I was THRILLED to find this invisible ink recipe. Many invisible ink recipes involve holding dried lemon juice messages over a candle and almost setting pieces of paper on fire. Luckily, this recipe doesn’t require any heat and is totally safe---besides the slightly strong scent of rubbing alcohol. However, with it warming up outside--this would be a great outside project!

Here’s how to make your own heat-free invisible ink:

Materials needed:

• 2 medium-size glass containers (I used Pyrex liquid measuring cups)
• Q-tips
• Paintbrushes
• Paper (white paper works best, you could also use cardstock!)
• Table covering
• Cookie sheet/craft tray
• 1 tsp powdered tumeric
• ½ cup rubbing alcohol
• 1 Tbsp baking soda
• ½ water

Directions (prep):

• Set up your experiment area, whether inside or outside, by protecting the area with some kind of covering. This could be a plastic tablecloth, trashbag, or some other non-absorbent material. 
• Place a cookie tray in the experiment area
• Gather all other materials and have them on hand. 

Directions (activity):

• Tell little ones that today you will be experimenting with invisible ink! 
• Invite them to help you mix 1 Tbsp of baking soda into ½ water in one of your glass containers
  • Mix until it is mostly dissolved and keep mixing throughout your experimenting--it doesn’t dissolve all that quickly. 
• Have little ones draw on their paper with the baking soda solution using q-tips
  • It will be hard to see what they are drawing! They can try writing words or just doing abstract doodles. Anything will be fun to find using the invisible ink decoder!
• Put aside the drawings to dry

• While they are drying, make your “decoding” solution
• Mix 1 tsp turmeric powder into ½ cup of rubbing alcohol 
  • The turmeric solution will stain hands and surfaces--so be careful while mixing and using this solution. At least it won’t set your house on fire, right?! 

• Once your papers are completely dry, place them on the cookie sheet and paint over them using the tumeric decoding solution. What happens?!?!
• Watch your paper change color more as they completely dry. 

The Science: 

(For younger scientists):

• Explain that the baking soda “ink” is changing color because it reacts or changes when it meets the turmeric solution. There is an ingredient in the turmeric that changes the baking soda to that very deep purple color when they meet! 

(For older scientists):

• Turmeric is a ph indicator. This means that it will change the color of different substances when it interacts with them to show us what their ph is. 
  • Ph tells us the acidity or basicity of items. 
  • Basically, substances go through a chemical reaction when they “meet” a ph indicator and that causes them to change color. 
  • Think about a traditional baking soda and vinegar experiment - they combine and erupt! That is because baking soda is a base and vinegar is an acid. If we tested the ph of vinegar it would be a very different color than the ph of baking soda. 
• When you paint over the baking soda papers with turmeric, we are seeing that deep purple appear because that is the color that baking soda changes when it interacts with a ph indicator.