Should be fun to see the dye results. My research says 700 grams of fresh madder roots will yield 100 grams of dried roots.
To use the dried roots, it is suggested to soak the roots in water for 24 hours; then place water in a blender & gradually add a few bits of root at a time until liquified.
Use this blend of water and roots to dye your mordanted wool or silk.
100 grams of dried madder roots will dye 300 grams fibre a lighter colour or 50grams fibre a darker shade.
Some believe that adding 6 grams calcium carbonate to the water to ensure you are using hard water will improve the colour.
Heat the madder roots and water gently to 160-170 degrees and just keep the temperature warm like this. After, strain the dye liquor through a very fine sieve to remove the madder pieces, etc. return to stove to keep warm.
Add your pre mordanted wet fibre to the dye pot and leave in for at least 2 hrs or even overnight, keeping the pot warm. Letting the fibre dry before you wash it will improve the colour too.
The next time I have a couple of days off I will try a pot of madder for dyeing some wool.