Design Practice 2: Invisible inks

1.

Lemon Juice

Lemon juice is a great example of a ‘heat-fixed’ invisible ink. An invisible lemon juice message, scrawled onto a piece of paper, can be developed by exposure to any heat source such as a radiator, an iron or a 100W light bulb.

Many acidic household liquids (Coca Cola, wine, apple, orange and onion juice included) behave in quite the same way, as do a number of bodily fluids. During the Nazi occupation of Poland, people frequently sent postcards containing hidden messages written in saliva and even urine.

Equipment & ingredients: you’ll find them in most local grocers

Suitable for: anyone

Ease of use: really easy

http://www.cartridgesave.co.uk/news/7-amazing-types-of-invisible-ink-how-you-can-use-them/

Invisible Ink with Lemon Juice

Making invisible ink is a lot of fun, you can pretend you are a secret agent as you keep all your secret codes and messages hidden from others. All you need is some basic household objects and the hidden power of lemon juice.

What you'll need: Half a lemon Water Spoon Bowl Cotton bud White paper Lamp or other light bulb Instructions: Squeeze some lemon juice into the bowl and add a few drops of water. Mix the water and lemon juice with the spoon. Dip the cotton bud into the mixture and write a message onto the white paper. Wait for the juice to dry so it becomes completely invisible. When you are ready to read your secret message or show it to someone else, heat the paper by holding it close to a light bulb. What's happening? Lemon juice is an organic substance that oxidizes and turns brown when heated. Diluting the lemon juice in water makes it very hard to notice when you apply it the paper, no one will be aware of its presence until it is heated and the secret message is revealed. Other substances which work in the same way include orange juice, honey, milk, onion juice, vinegar and wine. Invisible ink can also be made using chemical reactions or by viewing certain liquids under ultraviolet (UV) light. http://www.sciencekids.co.nz/experiments/invisibleink.html Due to the ink I found that developed in the light possibly not working due to it developing as it dried I looked at other alternatives. Lemon juice can be used as an invisible ink that can be seen when lifted to the light. This doesn't develop into an image but does kind of represent the idea of negatives being seen in the light.