Musings on Natural Dye Mordants

There are a lot of misconceptions being published on the internet when it comes to dyeing fabric, more specifically when using natural dyes or botanical dye printing.

Often when dyeing with natural dyes fabric needs to be mordanted for the dyes to adhere to the fabric better and create a richer, longer lasting color.  

A mordant is a fixative that allows dye molecules to bind to fiber. From the Latin word mordere, meaning to bite, a mordant is a chemical compound that can brighten a dye color, darken it, or make it colorfast. 

Mordants include tannic acid, alum, chrome alum, and certain salts of aluminum, chromium, copper, iron, iodine, potassium, sodium, tungsten and tin.  The most commonly and safest mordant used is alum, either aluminum sulfate or aluminum acetate.  

When botanical dye printing (aka ecodye) iron and copper are mostly used by rolling your bundle on an iron or copper pipe or using iron water.  Tannin plays a big part in this method when using leaves to dye print with.

A true mordant bonds with the fabric and the dye molecules.  

There are factors other than mordants that can help affect dye properties. These are called binders, assists, or modifiers.  These modifiers change the PH of the dye bath to accommodate the type of fiber used or they create a surface bond for the dye to affix to such as soy milk.  These are not true mordants.

I am seeing so many websites on the internet where people are giving recipes and information for mordanting and dyeing fibers/fabric.  However, it seems the definition of a mordant has changed from what I was taught by leading dye experts.  I see articles titled “How to Mordant with Soy Milk”, “Soda Ash as a Mordant”.  Technically those additives are not true mordants but assists or modifiers.  It seems that the terminology of a mordant has morphed into meaning “anything that helps set or changes the color of fiber/fabric dye”.  

I have brought this to the attention of some of the people who published those articles and the response is “We don’t really care about the science of it, just the results”.  I wonder if this will be the way of teaching in the future?   What does the term mordant mean to you?

I have taken extensive natural dye classes in the past with Michelle Wipplinger and Karen Cassleman.  This is written from my knowledge of what I remember learning from them.

Lorri Scott

lasfibers@yahoo.com