Sunday, 18 March 2012
Dyeing wool in the woods by Gillian Willis
Tomorrow 19th March 2012 will be a very exciting day in the woods indeed.
Helen, Lauren and I will be working together to introduce the children to the process of dyeing using natural materials.
We will be dressed as witches(good, friendly witches)who make magic potions to help people.
The reason behind this lesson is to show pupils that the fire can be used for a variety of reasons not just for cooking and keeping warm. They will also learn that everyday items found in the natural environment can be used as dyeing agents to produce beautiful colours.
We will ask leading questions to incourage thinking about fabrics that they are wearing and how the colours came about.
We will show the children how to dye wool using ewe bark, onion skins, blackberries and oak galls.They will predict what colours will be produced by each one and at the end they will see if they were correct.
Fingers crossed that they will all enjoy it!!!
Pics to follow!
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Gillian, you are going to hate me for this! How exactly does dyeing work? I noticed you mentioned iron salts in your blog entry about ink making, and I saw that you used iron salts or aluminium salts as "mordants" when you dyed in the woods - but can you help us understand the dyeing process by telling us some (simple?!) chemistry? Thanks!
ReplyDeleteDuncan...you are so right!! However, I will do my best to research this topic and get back to you!
ReplyDeleteA quick update for anyone wanting to know about our day in the woods with the children.....it was fantastic!! According to one young man 'The bestest day in the whole wide world'!
The children had a lovely time listening to us witches telling them all about what we do everyday in the woods. They were very eager to help us to create a 'magic potion' to change the colour of the wool.
The really enjoyed using the mortar and pestles to crush the tough oak galls and blackberries and seemed genuinely surprised to see the lovely colours produced in the end. All in all, it was a good day!
The dyeing process involves three factors: fabric, dye bath and mordant. Some natural dyes have a chemical make-up that will not allow them to bind with various fabrics and require the application of a mordant (the metal salt) solution to the fibres at some point in the dyeing process. This forms a bridge between the dye and the fibre. The metal ions adhere to the wool and serve as points of attachment for the dye molecules.
ReplyDeleteMordant comes from the French "mordre" to bite, it therefore cause the colour to 'bite' into the fabric. Mordants are metallic salts that fix a dye to a fabric by basically acting on the dye molecules, breaking apart existing links and forming new ones that will bind with the fabric. . It is basically the chemical link that fixes the dye to a substrate by combining with the dye pigment to form an insoluble compound. In the woods we used Potassium aluminium sulphate and Iron (ferrous sulphate) as our mordants.
The most commonly used mordant dyes have hydroxyl and carboxyl groups and are negatively charged, i.e. anionic. Some other mordant dyes may possess amino groups, and are cationic overall. Despite this, they must still have hydroxyl or carboxyl groups, since lake formation requires it. (The dye lake is an insoluble molecule formed when the complex of dye and mordant are combined, which then attaches to the wool.) Mordants increase the fastness of the dye since the larger molecule is now bonded to the fibre.
Wool is highly receptive toward mordants. Due to its amphoteric nature wool can absorb acids and bases equally effectively. When wool is treated with a metallic salt it hydrolyses the salt into an acidic and basic component. The basic component is absorbed at –COOH group and the acidic component is removed during washing
Wool is a protein, a naturally occurring polymer made up of amino acid repeating units. Many of the amino acid units have acidic or basic side chains that are ionized (charged).The presence of many charged groups in the structure of wool provides excellent binding sites for dye molecules, most of which are also charged.
Revise A2 Chemistry for Salters (OCR A Level Chemistry B)
Salters (OCR) Revise A2 Chemistry
If you find the above a bit puzzling, think of it this way, the mordant is a chemical that basically allows the dye to be fixed onto the wool, so that it does not wash off.
ReplyDeleteGillian
Please see my new post about How Dyeing Works!
ReplyDeleteThere is a thesis written by Charity Goetz, all about Textile dyes, very intersting if you want to find out more about the whole dyeing- mordant process, you can find it at:
ReplyDeletedigitalcommons.liberty.edu
Apart from the 2 books listed above, here is a list of websites used to inform this dye blog:
www.sewanee.edu
http://scioto.dublin.k12.oh.us
dictionary.reference.com
www.canadiantapestry.ca
www.earthues.com/aboutmordants.html
www.jagson.com/mordantdyes
en.wikipedia.org
www.answers.com