Cheryl Kolander, Master Natural Dyer, Aurora Silk, c 2002
Chrome mordant can be a wonderful tool for the home or art dyer. Lately there has been a lot of controversy about its use. Let us look at the science of Chrome mordant, so that we can each make an informed decision about personal use.
Chrome is not a “Heavy Metal” that crosses the blood-brain barrier, accumulates in the body and acts as a long term poison. Rather, Chrome is a “trace mineral”, that the body actually needs for health. For all trace minerals, the body has mechanisms for disposing of excess so they do not accumulate and cause long term health problems.
The oxidation state or valance of the Chrome changes as it is used. Using Chrome mordant (Potassium or Sodium bi-chromate) changes it from the hexavalent form, which is metabolized in small amounts by the body, into the trivalent form, which is easily metabolized by the body.(1)
Too much of any metal is toxic. A strong solution of Chrome mordant is sufficiently oxidative, it can cause chemical burns. Normal concentrations of Chrome mordant are not a hazard. However, weighing out Chrome mordent should be done with extra care, wearing gloves. A spill of the concentrated crystals onto damp skin could result in a burn. First aid is continuous rinsing in running water for 15 minutes, followed by St. John’s Wort (Hypericum) oil or salve.
Standard Laboratory Procedure should always be followed. At a minimum:
- Wear protective clothing: rubber gloves when working with any dye or mordant, and glasses to protect eyes from splatter.
- The workplace must be well ventilated. At least two windows need to be open at all times. An outward facing fan should be placed in one of them.
- Wipe up any spills. Spills dry and become dust that can be breathed into the lungs.
In the environment, pollution from chrome comes from many industrial and occult sources. The amount that a home/art dyer generates in waste is miniscule. Even this small amount can be minimized to almost nothing, through the economical methods of mordant re-use: The simplest way is to always mordant approximately the same weight of fibre each time. Figure that 25% (one quarter) of what was in the mordant bath to begin with is still there, after the mordanting process is complete. Wring out the fibre well into the used bath, then store the bath covered. It will last indefinitely. Re-charge by adding only 75% (three quarters) of the usual amount. Following these procedures, the home/art dyer only loses what goes out in the rinsing.
Chrome mordant is a useful tool for the home dyer. It produces the fastest richest tones from the gathered and growable dyes such as flowers, weeds, leaves and barks. For the art dyer it is indispensable for strong browns, jet black and unusual, extra fast hues with cochineal, madder and brazilwood. It is a mordant that can be used carefully and responsibly by the home/art dyer.
(1) Passwater, Richard, S., 1992, “Chromium Picolinate”. Keats Publishing: New Canaan, CT, USA
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