Name: azkhan

Message: I want to know whether copper sulphate, ferric chloride, and potassium permagnate can be used as mordants or not? If yes, then kindly provide some information about them. Can you compare natural and synthetic dyes?

Potassium permanganate is not used as a mordant for hand dyeing. It is used industrially to discharge (bleach out) indigo denim, but it is not recommended for this use at home because it is very toxic. It is also a serious explosion hazard if you allow a solution of potassium permanganate to dry up. See this discussion on the Dye Forum for more information: "Discharge Indigo with Potassium Permanganate".

You may be thinking of a very different potassium compound which has, ill-advisedly, been used as a mordant with natural dyes. Potassium dichromate is a known human carcinogen. Chromium is commonly available in two forms, the trivalent form and the hexavalent form. Potassium dichromate is in the hexavalent form. Hexavalent chromium has been responsible for many serious injuries and deaths due to industrial exposure. You should not bring this substance into your home, though you could use it in a properly equipped laboratory. It is very possibly illegal in your community for you to dispose of it in your trash or as wastewater. In contrast, chrome-complexed premetallized dyes such as some of the Lanaset dyes contain the much less dangerous trivalent form of chromium, and at much lower concentrations. (See "What does it mean when a dye is premetalized with chromium or some other heavy metal? What are the risks of exposure from using a dye that is premetalized with chromium?".)

Copper sulfate is also known as blue vitriol. It is used with logwood in dyeing blue, and with cutch, improving lightfastness while imparting a greenish tinge. Copper sulfate is poisonous and can be deadly when swallowed, and can also be hazardous to the environment, so use it with care and dispose of it correctly. Here is a link to a good article on the toxicity of copper sulfate.


Ferric chloride can be used as a mordant almost interchangeably with ferrous sulfate, but is considered superior for mordanting silk. Iron works to dull down colors; iron contamination in alum will ruin bright reds. Iron and tannins combined with logwood makes a good black. Ferric chloride  is less toxic than copper sulfate, but  can be deadly when swallowed, so, as with all mordants and most dyes, you must take appropriate safety precautions, and keep it well away from children. The Label Hazard Warning required for ferric chloride is as follows: "DANGER! CORROSIVE. CAUSES BURNS TO ANY AREA OF CONTACT. HARMFUL IF SWALLOWED OR INHALED. AFFECTS THE LIVER." Here is a link to an MSDS for ferric chloride. 

The only really safe mordants for natural dyes are alum and tannin. Of course they are not safe to swallow, but they are not deadly. Beginning dyers should not use copper sulfate or ferric chloride unless they have been trained in the safe use of toxic chemicals; even experienced dyers should not use potassium dichromate in their homes, where inadvertent exposures may contaminate living areas.

For more discussion comparing natural with synthetic dyes, see the following pages:

• "About Natural Dyes"

• "Aren't natural dyes safer than synthetic dyes?"

• "Natural Dyes Are Not Superior to Synthetic Dyes"

• "Fixing natural dyes from walnuts, goldenrod, sassafras and poke weed in
cotton - do I use urea or soda ash?"

• "A Science Fair Project on Artificial Dyes Versus Natural Dyes "

• "What's the difference between mordants and other chemical assistants used in dyeing?"

• "Natural Dyes", on the Dye Forum

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