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How Mordants Work – I think

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I’ve been doing some research trying to understand mordants a little better and how they react with everything on the base level. I don’t really understand it all and Chem 101 seems like ages ago and I’m pretty sure did not include this!

Here’s what I found:

Mordant from the Latin word “mordere” – to bite.

Mordants form a coordination complex with your dye substance and the fabric. This attaches the dye to the fabric so that it won’t wash right out.

A coordination complex occurs when iron atoms are bound to silk molecules and plant molecules forming this lovely little chemistry diagram.

From what I understand the iron and rust atoms that are forming this mordant coordination complex attach themselves to the molecules of both the silk and the plant material making these into ligands.

The ligands are the silk or plant molecules bound to iron atoms by coordinate covalent bonds {sharing of pairs of electrons between atoms – in this case one lone pair being shared with the iron or rusty atoms} forming the first coordination sphere.

The first coordination sphere is the ligand directly attached to the metal base atom.

So when you dye, iron and rust molecules grab lone electron pairs from both your solvent dye substance and your fabric and bond them together. Hopefully permanently.

I think :)

What I want to know is:

How does tannin in leaves effect this bonding process?

I’ve read that tannins in a leaf will react with the iron in the water to form better prints.


If anybody has any information on the chemical composition of the dye process I would love to hear from you. And please correct my chemistry if it needs it. This is a learning process and I really do want to know.

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