Not every fiber or fabric can be dyed with natural dyes. Synthetic fibers are not suitable for dyes because the fibers do not absorb the dyes. Likewise fabrics made from synthetic fibers cannot be dyed. Thus look for fibers and fabrics that are derived from nature.
Fibers from animal origine such as silk and wool are suitable for dyeing since the fibers can be opened up enough to allow dyes to penetrate into it. Also the fabrics that are made out of these fibers are suitable for dyeing. For instance Chiffon-silk or felt are perfect and beginner friendly fabrics to dye.
Fibers made from plant fibers are also suitable for dyeing with natural colours. Cotton, Linen, Flax and other so called cellulose based fibers take up colour.
If you stick to animal and plan based fibers and fabrics you can easily expand your dyables arsenal.
The most obvious base colour of your fibers and fabrics is natural. Wool, cotton, linen and flax products often come naturally in light beige colours which are perfect for your dyeing needs.
These materials sometimes also come in darker colours, such as grey wool or more darker plant fibers. These can still be dyed and will give you interesting mottled or muted colours.
If you dye silk or wool white colours will give the brightest colours. Be aware though that some wools or silks are bleached which will affect the effect your dyes have.
It is hard or in most cases impossible to colour over existing dyed materials because natural dyes are so subtle.
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