Collecting bits of cloth and the clues they hold

Cloth holds many clues. What it is made of and where it came from are just the start. What is stuck to it tells a great deal more to add to the total picture.

To the right is a magnified photograph of a piece of cloth. What is the stain? I know because I photographed it. It is apricot nectar with traces of chicken and packet French Onion soup.

The knitted jumper has a very fine hair on it which was barely visible to the naked eye. Again, I know exactly who it came from. She's a very small dog named Epsilon-pi.

A commonly used method to lift fibres and debris from cloth is quite simple. Apply a piece of sticky tape to the cloth surface and see what comes off. This is done in a systematic process to make sure every part of the cloth or garment is covered.

Fibres from both within the cloth, and those attached to it, are then tested, such as by applying a burn test. The fibre or yarn is held with metal tweezers or tongs. It is then moved slowly towards the flame. It is observed carefully as it approaches the flame because some fibres will shrink away from the flame before entering it, while others will melt as they approach. If it does neither of those, the fibre is closely observed as it burns. There are  many clues as to exactly what fibre it is including:

* how it burns.
* if it continues burning when it has been removed from the flame.
* if it produces smoke. If so what colour and texture is the smoke?
* if it produces any odour. If so, what does it smell like?
* if it forms a soft ash or a hard glassy bead after burning?
* if it is thermoplastic.

Fibres that shrink as they reach the heat of the flame, melt before they burn and then leave a small hard bead after they have burnt, are known as thermoplastic. Natural fibres are not thermoplastic. Many synthetic fibres are.

Non-thermoplastic fibres include cellulose, protein and some synthetics.

1. Optional: Explore these results by trying the burning tests on a range of samples of cloth and yarn.

Please only do this task with teacher or parent permission!

If you do decide to do this task, you need to be systematic, not just burn everything in a bonfire on the desk! Take each fibre and record the result for each of the 6 points above.

Then take a second sample of one of your materials and have someone else burn it. Can they identify it using your table of results?

2. Identify the piece of orange cloth in the two photographs.

It was found at a crime science, torn from something the criminal was wearing or carrying. It is common around all homes.

What is it?

Note that there are hairs, probably from the criminal, attached. Look closely at items in your bedroom and bathroom. How many have hairs attached?
Use a magnifying glass to have  a close look at the material of the clothes you are wearing. In particular, look at a jacket or other item which could be left at a crime scene. Search for any signs of food, dogs, dirt, oil, dandruff ... anything on the clothes which may give clues as to the owner.

3. Study the cloth you are wearing with a magnifying glass. Use sticky tape to lift fibres and other material from your clothes.

Can you see things stuck to it like the fine dog hair on the knitted jumper? What are they? What does it tell about you?

Include your sticky tape samples with your response.