- Retractable or Collapsible Brushes. If you shake-clean these types of makeup brushes, water may become trapped between the movable parts.
- Non-traditional makeup brushes. In which the hair is inserted directly into a wood or plastic handle, without a traditional ferrule. This includes Benefit Cosmetics’ free brushes that come in their Box O’ Powder product, as well as the MAC Masterclass or Artis line of brushes, or similar niche brushes.
- Bejeweled brushes. Like this gorgeous $175 set from jewelry designer Alexis Bittar. Any makeup brushes with jewels or jewel-like decorations should not be shake-cleaned in My Brush Betty, as the pretty doodads may become dislodged.
In the rare instance that you experience a problem shake-cleaning a makeup brush, please report your experience as soon as possible to firstname.lastname@example.org.
— My Brush Betty