The Science Of Acids Part 3

Acidic Art
There is an artist called Gustav Metzger (hyperlink to MOMA and Spacex) who uses science to make art and to make statements about the world we live in. In one of his works, called "Acid on Glass", he sprays a strong acid called hydrochloric acid onto some nylon and the acid burns holes into it. (photo of Gustav and acid art) He calls this "Autodestructive Art". You can do your own safe version at home to create pieces of art or even to send secret messages, here's how..
Dr. Bunhead says you need these!
  • some paper to write on
  • lemon juice (bottled or freshly squeezed)
  • a fountain pen or cotton bud
Dr. Bunhead says try this!
Dip the pen or cotton bud into the lemon juice. Write over your sheet of paper with fairly thick strokes for the best results. As you write the 'invisible ink' will dry and vanish before your eyes. You can make your picture reappear by warming the sheet.

Dr. Bunhead says,


You must get an adult to do this bit. Warm the sheet, written side down, over an electric cooker element, candle flame or a stove. Alternatively, iron it on medium heat setting.

As the writing warms up it gradually becomes brown and visible again. This is where the acids in the lemon juice are being heated up and 'burn' through the paper. If you heat it long enough the lemon juice will completely eat through the paper to leave holes in the shape of whatever you drew. This is how you can make your own autodestructive art picture. You are destroying something (the paper) to make something else (the image left by the burnt away paper).
Did you know?
Many years ago, before the age of electronics, secret messages were passed using special inks to stop other people reading them. You can use the above recipe as 'invisible ink'. When you use this ink you can see what you write; but as soon as it has dried the writing becomes invisible. You can send secret messages to friends, but don't write their address in invisible ink! They can then read them by warming up the paper.
Edible Acid Machine
Let's take a last look at acids and make an edible acid machine.
Dr. Bunhead says you need these!
  • 2 teaspoons of citric acid crystals. You can buy this from a chemist's shop.
  • 1 teaspoon of bicarbonate of soda
  • 6 teaspoons of icing sugar
Dr. Bunhead says try this!

CAUTION Normally you would not put any chemicals in your mouth but the ones in this experiment are all safe to eat.

Mix up all the ingredients. Put some of the mixture in your mouth. What happens?

You feel a tingly, fizzy sensation.

In this experiment the citric acid and bicarbonate of soda are being destroyed. As they are destroyed carbon dioxide gas is created. You are making something by destroying something else. The carbon dioxide that is made is an acid so it tastes sour on your tongue. The icing sugar makes it also taste sweet and so it's enjoyable to eat. Well done... you've just made autodestructive edible acid machine! Try the experiment again but this time leave out the sugar.

You will notice that it still fizzes, because the carbon dioxide gas is still made which is what makes it fizz. However, now there is no sweetness from the sugar so it just tastes sour...yuck! Now you can see why they add sugar.

Did you know?

Citric acid is one of the acids found in lemons, oranges and limes. That is why they are called 'citric fruit'. The other acid in lemons and other citric fruit is called ascorbic acid. This is more usually called vitamin C. Potatoes also have vitamin C in them.

Vitamin C is a very important acid. Human beings are one of the few animals (along with guinea pigs) that can't make their own vitamin C in their bodies. So we have to get it by eating it. If we don't get enough we get a disease called 'Scurvy'. In the old days sailors on long voyages used to get this. It made their skin go purple and blotchy, their gums would bleed and their teeth fell out. Eventually they would die from it.

After many sailors had died the British Navy started giving sailors limes as they were found to prevent scurvy. Because of this British sailors were called 'Limeys'. Scientists knew that an acid in the limes (and other citric fruit) stopped the scurvy and so they named it 'ascorbic acid' from the Greek word for 'no scurvy'. Later they discovered this acid also had a special chemical part in it called an 'amine'. They knew it was a vital chemical for our bodies so it was called a 'vital amine' which is where the word 'vitamin' comes from. It was called vitamin C because two other vitamins had already been discovered. These were called vitamin A and vitamin B.


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