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SCIENCE / DESIGN & TECHNOLOGY

COMPARING NATURAL AND SYNTHETIC DYES

Objectives

  • To extract natural dyes.
  • To observe the effect of natural and synthetic dyes on a range of fabric types.

Curriculum links

English National Curriculum:
Science 3: 2a, 2b
Design Technology: 4a

Gateway story

Both natural and synthetic dyes are used today - synthetic ones being more commonly used. The same dye (whether natural or synthetic) used on a range of fabric types will result in different colours.

Gateway elements

  • Animation
  • Piece of dyed multifibre
  • Fabric being dyed in industry
  • Fabric being dyed traditionally
  • Children dressing up in a range of brightly dyed clothing.

Animation: The chameleon dyes all his clothes, as he is wearing them, to fit into the 'yellow' world. When he looks at the washing on the line, they all different shades of yellow, even though they were all dyed in the same dye-bath. Note: The animation can be paused to emphasise discussion points.

Dyed multifibre: Multifibre, as its name suggests, is made up of several types of fibre or fabric. These are (from left to right) acetate, cotton, nylon, polyester, acrylic and wool. This piece of multifibre has been dyed with turmeric.

Gateway discussion

Whilst looking at the gateway, ask the children some of the following questions:

  • What is a natural dye?
  • What is a synthetic dye?
  • What do you think multifibre is (are there any clues in the picture and the name?)?
  • What is the chameleon doing? What has happened to all of his clothes after jumping in the dye? Why?


Approximate time required: 2 hours

Resources needed

Per class of 30 children:

Dyeing naturally sheet
Optional display of plants, vegetables and flowers used for natural dyes (see lists below)
30g red cabbage (1 leaf)
30g onion skins (5-6 onions)
5g turmeric or 30g chamomile flowers
Measuring jug (about 500 ml)
Cooker hob
Old pan
Old spoon for stirring
Rubber gloves
Fine sieve
2m strip of Multi-fibre strip (see List of Suppliers )
3 packets of synthetic dye (blue, yellow and brown) - from hardware/department stores
Fixative (to be bought with cold water dyes only)
Kitchen salt (a minimum of 15 tablespoons, to 'fix' natural dyes to the fabric)
Washing line and pegs - optional
Commercial dye colour chart -from hardware/department stores

Note: Turmeric produces a vibrant shade of yellow but requires about 30 minutes settling time after boiling in the dyebath. Chamomile (available as tea bags from health food shops) also produces a yellow dye and can be strained in seconds.

SAFETY NOTE

Extracting and using the dyes should be carried out with adult supervision and any part of the activity using boiling water must be carried out by the teacher. Rubber gloves should be worn whenever the dyes are handled.

Organisation

Initial class discussion followed by group work.

Advance preparation

The strip of multi-fibre should be cut into 10 x 10 cm squares. The 'acetate' end of each square should be marked in some way, e.g. indelible ink. Otherwise, it is hard to identify the fibre once the identification label has been removed.

If a lack of time, supervision or equipment does not permit the children to extract dyes, these can be prepared before the lesson and displayed in transparent, sealed containers alongside their sources.

Carrying out the activity

A display of plants, vegetables and flowers, whose colours are used in dyes, makes an attractive starting point for this activity and provides a useful focus for discussion of natural dyes. For ideas on which plants to include, go to the Background Information below and Sources for Natural Dyestuffs.
The children extract the natural dyes following the recipe given and dye pieces of multi-fibre strip using natural and synthetic dyes. Each group uses the same colour of natural and synthetic dye, in order to make comparisons. So, in a class of 30 children divided into groups of five, two groups would use each colour.

Recipe for a natural dye

The leaves/flowers, etc. used to obtain the colour are referred to as the dyestuff.

Ingredients: 30g dyestuff (5g if using turmeric)
250 ml water
1 tablespoon kitchen salt

1. Pour the water in an old pan and add the dyestuff.
2. Bring the mixture to the boil and boil for 15 minutes, topping up the water when necessary to maintain a constant volume.
3. Strain the dyebath and reserve for use with the fabric.

Dyeing the fabric with a natural dye

  1. Add hot or cold water to the dyebath to obtain a warm temperature to improve the take up of the dye .
  2. Add 15g fabric, which has been pre-soaked in warm water, to the dyebath.
  3. Bring the dyebath to the boil and simmer for 45 minutes. Even if the colour is quickly transmitted, leave for the required time so it becomes fast and even.
  4. Cool the dyebath naturally and rinse the fabric in cool water.
  5. Dry the fabric on a washing line across the room or on a radiator.

Dyeing the fabric with a synthetic dye

Instructions for use are given in the packet. A packet of fixative and kitchen salt (4 tablespoons per packet) are required when using cold water dyes. The fabric is steeped in the dyebath for an hour, stirring for the first 10 minutes. The fabric is rinsed in cold water (as for the natural dyes), rather than washed in soapy water.

Comparing the dyes

Once the fabric is dyed and dried, the groups cut and attach strips of the fabric to their Dyeing naturally record sheet, to make a visual comparison. Children also use the sheet to record their observations about the colours produced by the two dyes on the different fabric types.

A colourful collective display can be made of the results of the investigations, showing the colours and how they were obtained.

Background information

Plants or flowers giving a colour-fast dye are called substantive and those needing a fixative are called fugitive. A classroom display of dyestuffs could be divided into these two categories.

Substantive dyes

coffee (used coffee grains)
henna (powder or leaf)
avocado (skins)
seaweed (bladder-wrack)
blackberries
mustard
acorns
grass
onion skins
saffron red
cabbage
beetroot

Fugitive dyes

elder (leaves and berries)
bracken
chamomile flowers
dahlia
cochineal
daffodil flowers
turmeric

There are many other plants, barks and flowers that can be used. Flowers offer interesting dyestuffs, as the majority give shades of yellow or green; even though the flowers themselves may naturally be bright and vivid!

Natural dyes have been used for thousands of years. The first commercial synthetic dye was discovered in 1856 in the UK by William Henry Perkin. It was a purple dye, often referred to as Perkin's Purple. Until this dye was discovered, a dress dyed purple could start fading in a few hours! The book 'Mauve' by Simon Garfield tells the story (pub. Faber) ISBN 0-571-20197-0.

Synthetic dyes give bright and vivid colours, many natural dyes do not. A greater range of colours and shades is available from synthetic rather than natural dyes. Comparing the colours produced with a commercial colour chart emphasizes this point.

The same dye has quite different effects on different fabrics. For example, some synthetic dyes are made specifically to dye cotton or others to dye acrylic, and will not colour other fabrics or will not produce the desired colour on other fabrics.

The multi-fibre fabric used in this activity is produced for the colour industry for testing dyes.

It has a very high specification for each fabric and industry uses it to test the quality and effectiveness of dyes. In this way, they can ensure that the high standards required of their dyes are met.

Extensions / links

Science

Quality testing of dyes
has been written to follow this activity. Children test each dye's resistance to sunlight, detergents and friction.