14 Things You Should Know Before Getting a Perm

Each head of hair reacts differently. According to Joico guest artist Drea Lecher, timing depends on the client's hair texture, if they had any previous color services and the kind of wave they want. Processing times can go from as little as three minutes up to 20. To prevent hair from processing too far, Lecher says it's important that strands are tested every three to five minutes, especially if hair was previously colored.

Rizzo agrees and says timing also varies depending on how porous hair is. "When hair is porous, it absorbs faster, meaning your hair follicles are open [to] taking in products faster than if your hair wasn't porous," she says. 

Image via @rachelgoodwinmakeup