Science Smarts: Secret messages

By PATTY ROOKS on November 19, 2021.

I know as the cold weather is more and more frequent, many of us are looking for some fun activities to keep on hand for those young scientists to do inside. Not to mention, I think I may have the “Holiday bug” – I see decorations, lights and gift ideas everywhere!

With that being said, I have been stocking up on all things holiday. One thing that I may have gone a bit crazy with are the cranberries… I had better use some up before someone notices!

Let’s get started.

Remember to ask an adult before doing this experiment.

Materials

• Stove

• Adult helper

• Small pot

• Cranberries

• Cranberry juice

• White paper

• Baking soda

• paintbrushes

• Water

• Measuring spoons

• Measuring cups

• Stirring spoon

• Strainer

• Hot water

• Clear jar

• Spray bottle

Procedure

• Measure 250 mL (one cup) of fresh cranberries in a small pot. Add 125 mL (1/2 cup) of cranberry juice. Mash the cranberries into the juice as it cooks. Be careful you do not splash and burn yourself.

• Have the adult helper place this over medium heat, allowing it to come to a boil, stirring frequently. Allow this to gently boil for five minutes.

• Set aside to cool.

• Once cool, strain this mixture into the spray bottle.

• In a clear jar, measure 60 mL (1/4 cup of hot water). Add 60 mL (four tablespoons) of baking soda. Mix well and set aside.

• Take a piece of paper and paintbrush.

• Use the baking soda mixture to write your secret message onto the paper.

• Allow this piece of paper to dry.

• Once dry, and if you want to read the message, gently mist the cranberry mixture to reveal the message.

What is going on?

This may seem like “magic” but as I have mentioned before it is SCIENCE!

Cranberries are not only delicious, but are also a great ingredient in science experiments. This is because they contain a substance called anthocyanin. Anthocyanins are the pigments that give cranberries their vibrant red colour.

Two more things are going on here. When you made the baking soda solution, you created a “base” solution. This means it has a pH of more than than seven. The cranberry solution is actually acidic with a pH of about 2.5.

The invisible ink you used to write your secret message with, the baking soda mixture is a base. Once it was dry, you could no longer see it, this is why I called it a “secret message.” To get it to reappear, you need to gently spray the message with the cranberry solution which will start out red and once in contact with the base, it should turn a greenish colour revealing what you wrote!

Patty Rooks, Senior Scientific Consultant PRAXIS, “Connecting Science To The Community”. Contact Praxis at praxis@praxismh.ca, http://www.praxismh.ca, Tweet or follow us @PraxisMedHat, or friend us on Facebook. We are located at #12 826 11 Street S. E., Medicine Hat, Alberta, T1A 1T7 Phone: 403.527.5365, email: praxis@praxismh.ca.

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