In order for hematein to attach itself to the nuclear components within a cell, a mordant must be present. A mordant is a chemical that serves as a link between the dye and the substrate. The result is an insoluble compound that helps adhere the dye to the cells.
The most useful mordants for hematoxylin are salts of aluminum, iron, tungsten, and occasionally lead. These are classified respectively as :
- Alum hematoxylins
- Iron hematoxylins
- Tungsten hematoxylins
- Lead hematoxylins
The type of mordant used influences the type of tissue components stained and the final color.
Most mordants are combined into the staining solution, although a pre-treatment with the mordant is required with some hematoxylin stains.