This is one of many tests to determine a yarns’ content.
1.Find a small jar with a lid and add an ounce or two of domestic bleach (Clorox/ Javex).
2.Drop in a small length of yarn and replace lid.
3. Set aside overnight. Check progress sooner, if you wish or curious.
If, the yarn sample is wool or another natural fibre, it will be completely dissolved in a day or sooner. If, it is a mix of yarn fibres, the natural part will have disappeared, but the synthetic one will remain.
If, the fibre is acrylic or other man made one, it will remain the same as when it went into the potion.