Page 37 - Curriculum Visions Dynamic Book

 A traditionally dyed cotton rug from Afghanistan.
dye: a coloured substance that will stick to another substance, so that both appear coloured.
gelatinous: a term meaning made with water. Because
a gelatinous precipitate is mostly water, it is of a similar density to water and will float or lie suspended in the liquid.
mordant: any chemical that allows dyes to stick to other substances.
suspension: tiny particles suspended in a liquid.
Mordants for dyeing
Dyes will not easily stick to some natural fabrics such as cotton. So the fabric has to be
treated with a special chemical that attracts the fabric and also the dye.
Alum is a mordant, a material that will mix with water in a solution to produce a precipitate that sticks fast to cotton
fabric dipped in it.
 The precipitate, with dye stuck to the surfaces of the particles,
has completely settled, leaving only a colourless liquid above,
clearly showing that the aluminium hydroxide
formed from the alum is an effective mordant.
 A suspension
of freshly precipitated aluminium hydroxide
is added to the dye and thoroughly shaken.
Also...
Modern “fibre-active” dyes actually bond
to the fabric. For this reason they have a wider application than the traditional mordant, especially in the dyeing of synthetics, where mordants will not work.
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