Why do I have a white core in the fiber after dyeing?
What is happening when hand dyeing and the core is remaining white? Over the last 33 years that I have been in this business it is the most asked question about dyeing and the most easily solved. The first assumption is that there is something wrong with the wool-that there is a synthetic fiber in it that is resistant to the dye.
Every time we have been able to solve the problem by slowing down the dye process by starting the water at room temperature instead of hot. It is possible that you have been successful when starting the water at a hot temperature many times but a slight change in the acidity of the water or fabric can cause “striking” (when the core is not penetrated).
Remember, of course, to have your wool properly soaked before dyeing.