Alum
Alum mordant that is used for mordanting textiles when dyeing with natural dyes, is generally potassium alum (see below) but potassium alum is only one of very many different types of alum. Most of these are not suitable for use as mordants. Alums are double sulfates of sodium, potassium, ammonium and several other cations with a metal ion such as aluminium, iron and many others. For further information see the Wikipedia article on alums.
Calcium carbonate
Calcium carbonate is a common substance found in rock all over the world, and is the main component of shells of marine organisms, pearls, snails and in eggshells. It is found in aragonite, calcite, chalk, limestone and marble and its chemical formula is CaCO3. Calcium carbonate is the active ingredient in agricultural lime and is the principal cause of hard water. It is commonly used as a calcium supplement or as an antacid.
Chalk
Chalk is often used as a synonym for calcium carbonate but be careful when buying chalk for dyeing as the name may also be used for several other substances which are not effective for dyeing. The chalk sold in outdoor shops for rock climbing (magnesium carbonate) is not suitable and neither is school board chalk (calcium sulphate) or agricultural lime (calcium hydroxide).
Cream of tartar
Cream of tartar, or potassium bitartrate, is a white crystalline powder (also known as potassium hydrogen tartrate, potassium acid tartrate, and monopotassium tartrate) and has the formula KC4H5O6. It is a by-product of winemaking and is the potassium acid salt of tartaric acid. Don’t buy cream of tartar sold for baking unless it is clearly labelled potassium bitartrate, as it is often a cream of tartar substitute that is not effective in dyeing (often sodium pyrophosphate).
Potassium alum
Potassium alum or alum mordant (also called potash alum or potassium aluminium sulfate) is the potassium double sulfate of aluminium. Its chemical formula is KAl(SO4)2 and it is commonly found in its dodecahydrate form as KAl(SO4)2·12(H2O). It is commonly used in water purification, leather tanning, fireproofing textiles and in baking powder as well as a mordant for dyeing textiles.
Sulphate is the British spelling of sulfate. They are the same thing…
|
