Hard Water and Natural Dyes: What Your Tap Does to the Shade

Two dyers can follow the same notes with bark from the same bag and get different colors. When that happens the difference is usually the water. It is the largest ingredient in the pot and the one nobody weighs.

What hard water is

Hardness is dissolved calcium and magnesium, picked up as water passes through limestone and chalk. The U.S. Geological Survey sorts it into four bands, measured as calcium carbonate:

Your water supplier publishes the figure in its annual water quality report, and limescale in the kettle is a fair sign without one.

What it does to a bark bath

• It raises the pH. Hard water is usually alkaline, and alkali moves this color away from rose and plum. Using pH to steer the shade shows how far a small shift goes.
• The minerals bind with tannin. Some of the color that should reach the fiber is tied up in the water instead, so the result is paler and flatter.
• Iron saddens it. Well water and old pipes can carry iron, and even a trace turns a tannin dye toward grey. Useful when you mean it, unwelcome when you do not.
• Chlorine dulls some shades. City water is chlorinated. Filling the pot the night before and leaving it uncovered lets most of it escape.

How to check your own water

Dip a pH test strip in a glass of cold tap water. A reading near 7 is neutral and fine to use as it comes. A reading of 8 or more means the water will push the bath alkaline. For iron, look at the sink and the toilet cistern: orange-brown staining means it is there.

What to do about it

• Use rainwater or distilled water for the dye bath. Rain is naturally soft and slightly acidic, which suits this bark well. The dye bath is the pot that matters most; scouring and rinsing can stay on tap water.
• Or correct the tap water. Add white vinegar or citric acid a teaspoon at a time, stirring and testing, until the bath reads about pH 5 or 6. Do this before the bark goes in.
• Keep iron out. Use a stainless steel or unchipped enamel pot, and stainless or wooden tools. A cast iron or rusty pot acts as an iron modifier whether you want one or not.
• Rinse in the water you dyed in, if you can. A hard-water rinse can shift a finished color slightly.

Keep a note of it

Write the water down with everything else: tap, rain or distilled, and the pH if you measured it. It is the detail most often missing when a color cannot be repeated. Testing a dye before you commit a fleece covers the rest of the sampling routine, and the state pages carry tap water notes for many states.