Mordanting - period by period - and method.

The earliest European evidence of mordanting date back to Bronze Age finds, and was exclusively done with alum. The German Halberstadt finds are from a mining community where alum was present. We know that both Greeks and Turks mordanted with alum, ferrosulphate and copper sulphate, but there is no evidence that this knowledge reached furter north until later.

Wool - both raw wool, spun yarn, and fabrics - can be mordanted with 15 to 20% alum. It will not harm either dyer or yarn, and residue is removed when washing the finished product.

Later, in Roman Iron age and early viking finds, there is evidence of the use of sodium dichromate, potassium bitartrate, oxalic acid, copper sulphate, and tin salt. Presumably, trade routes south and east brought both the knowledge and the materials here.

The first evidence of imported dyestuffs rather than finished cloth came with the Viking trade routes along the great Russian rivers south. It is known that Swedish Vikings were hired as palace guards both in the Kiev court, and at the Imperial court in Constantinople (present-day Istanbul), and that merchants brought home both cochineal, indigo, and the knowledge of using them.

In southern Europe, there was wide-spread trade across the Mediterranean, and especially Spanish and Italian dyers were famous for producing varieties of colour that were otherwise unobtainable.

By 1400, all of the mordanting agents known today were widely used, and available to purchase even outside the dyer's guilds. Thus, even those who could not afford dyer's cloth could produce a wide range of fairly permanent colours themselves.

Many blends of chemicals were used - varying from dyer to dyer - to produce different colours from differing agents. I have listed the most common below, as well as their general influence on colours.

Note: sodium dichromate, which is essential in producing some browns, is both toxic and carcinogenic. If you choose to use it, ALL LIQUID WASTE must be disposed of safely at a toxic waste facility, and rubber gloves and face mask must be worn all through the process.

The percentages listed are percentage of DRY WEIGHT of material to be dyed! and only applies to wool. Instructions for linen and silk will follow.

The pot for mordanting must be either enamel, stainless steel, or clay to avoid contamination with unwanted metal ions. Until the first enamel pots arrived around 1600, glazed clay vessels were used, both by professional dyers and 'serious amateurs'.

Amounts - can be taken as a 'rule of thumb'. These are well proven!

For yellows:
1) 15 - 20% alum
2) 15% alum + 10% copper sulphate + 5% potassium bitartrate

For clear yellows and greenish colours:
3) 18% alum + 1-2% tin salt

For reds and oranges:
4) 18% alum + 9% potassium bitartrate
5) 15% alum + 5 - 10% oxalic acid

For yellow-browns:
6) 5% sodium dichromate + 10% potassium bitartrate

For dark browns:
7) 5% sodium dichromate

Method:

Weigh your material. Yarn hanks must be loosely tied in 3 - 4 places, raw wool placed in mesh bag, fabric unfolded. All must be freshly washed in pure soap and well rinsed.

Place material in lukewarm water to soak for 30 minutes.

Meanwhile, measure out your mordanting agent and dissolve in small amount of water in pot. Fill up with enough water to float and cover yarn/fabric.

Add yarn/fabric, and heat slowly to 90 degrees centigrade. While the bath is heating, keep material in constant, light motion to avoid uneven distribution of mordant in material. Keep bath at 90 degrees for an hour, ocasionally turning material over.
Remove from heat, and allow to cool overnight.
If you hae the possibility, it is preferable to let material remain in mordant bath until the dye bath is ready. I prefer to transfer yarn to buckets with lids, covering with mordant liquid, and let stand. Fabrics should be removed from pot the next day, shaken out, and dried.

If you mordant yarn for later use, let it stand for 24 hours, then shake it out, wring lightly, and dry in the shade. Store in clearly marked bags - it may be stored for up to 6 months before using.

Material mordanted with sodium dichromate will be ruined by daylight (permanent yellowish stains). While processing it must be kept UNDER the surface of liquid, and covered by lid - after mordanting, it must be dried in a dark place and stored in black plastic bags until used.

Be careful with measuring, washing and heating. Sloppy work with the mordanting will give you blotchy yarn/fabric, and less colourfast dyes!

Pre-mordanted yarn should be either rinsed or washed immediately before dyeing. For clear, light colours, washing is recommended - for darker colours, careful rinsing/soaking in clean water is sufficient.