Synthetic dye decided which colours ordinary people could wear

Colour used to be grown, dug or collected

Before the middle of the nineteenth century, every dye came from a plant, an insect, a mollusc or a mineral. Madder root gave reds, woad and indigo gave blues, weld and various barks gave yellows, and a scale insect gave the brilliant crimson known as cochineal.

Each of these had to be cultivated or harvested, transported, and processed, and the yields were often poor. A dyer needed skill and equipment, and the results varied between batches in ways no amount of care fully eliminated.

Because of that, colour was priced like any other agricultural commodity. Some shades were cheap and local. Others were expensive imports, and a few were extraordinarily costly, which is why sumptuary laws in various periods restricted certain colours to certain ranks. The restriction was partly social and partly a reflection of what things actually cost.

Fastness was the real limitation

The bigger problem was not obtaining a colour but keeping it. Many natural dyes bind weakly and fade quickly in sunlight or wash out, and the standard remedy was a mordant — a metallic salt applied to the fibre that forms a bridge between the dye molecule and the material.

Mordanting is chemistry that was practised long before it was understood, and the choice of mordant changes the resulting colour as well as its durability, so the same dyestuff could yield several shades depending on the process.

Indigo is the famous exception, because it works by a different route: it is insoluble, so it has to be chemically reduced into a soluble form, absorbed by the fibre, and then oxidised back to a pigment trapped in place. That is why an indigo vat is a living, managed thing and why the cloth turns blue in the air as it is lifted out.

A laboratory accident in 1856

The first synthetic dye was produced by accident. A young chemistry student in London, attempting to synthesise quinine from coal tar derivatives, obtained instead a purple substance that dyed silk brilliantly and resisted washing and light better than the natural purples available.

The commercial significance was immediate. Coal tar was a waste product of the gas industry, abundant and cheap, and here was a colour derived from it that had previously been among the most expensive available.

What followed was a rapid expansion of synthetic dye chemistry across Europe, and a whole industry grew from it. Within a few decades the major natural dyes had synthetic equivalents, including alizarin, the colouring principle of madder, and eventually indigo itself.

What that did to agriculture and to wardrobes

The effect on the countries growing dye crops was severe. Madder cultivation and indigo plantation agriculture had been substantial industries, and synthetic replacements undercut them in a way that reorganised regional economies and labour patterns.

The effect on clothing was equally large and considerably more cheerful. Bright, fast colour became affordable, consistent between batches, and available in shades that had no natural equivalent at all. The visual character of ordinary clothing changed within a generation.

It also made industrial-scale garment production practical in a way it had not been. A factory can only make identical garments if it can obtain identical cloth, and reproducible colour is part of that.

New fibres needed new dyes

The story did not end there, because synthetic fibres created a fresh problem. Polyester is hydrophobic and dense, and the water-based dyes that work on cotton and wool simply cannot get into it.

The answer was disperse dyes, which are applied as a fine suspension and driven into the fibre under heat and pressure. That is why polyester holds colour so tenaciously against washing, and why it cannot practically be dyed at home.

It is also why blended fabrics have to be dyed in two stages with two chemistries, and why the components can end up slightly out of step. A cotton and polyester shirt that has faded unevenly is showing you two dye systems ageing at different rates.

Reading the palette of old clothing

One consequence of all this is that colour dates a garment. Certain shades were unavailable, unaffordable or unstable before particular points, and the arrival of each new dye class shows up in what people wore shortly afterwards.

The muted quality that vintage textiles often have is partly the dyes themselves and partly a century of light doing its work. Faded is not the same as originally soft, and it is easy to mistake one for the other when looking at old cloth.

And the older restrictions have left traces in language and convention. Colours once associated with expense or with specific ranks retain some of that association long after the cost disappeared, which is a reasonably typical outcome for anything in clothing: the practical cause vanishes and the meaning stays behind.