Please view the Cleaning Cautions section before proceeding. Remember this information is a suggestion and you proceed at your own risk.
Nutshells are not made of wood, but are the hard outer covering of a nut that protects the kernel, or edible part, of certain wood species. The nutshell needs to be durable enough to be made into a button like like Brazil, black walnut, filberts, hazelnut, walnut, and coconut shells. Avocado pits and Corozo or Tunga nuts (Vegetable Ivory) are actually the hard core of the seed and not a nutshell; see appropriate Guide.
While similar in texture to wood, nutshells are biodegradable so extra care is needed. Just like gourd and wooden buttons they can be decorated with dyes, especially the coconut shell, which are being sold under certain button brands. Most brands state on the button card if they are safe for washing or not.
Colorfast Test before Cleaning
Gently dab a small inconspicuous area of the button with a damp cloth to check if any of the finishes will bleed. If it does, be extremely cautious using water even for tough stains.