Round brushes may have cores made from all of the following EXCEPT which material?

• A. Leather
• B. Nylon
• C. Ceramic
• D. Aluminum

Answer: (A)

Round brush cores are the internal material that gives the tool its shape, durability, and how heat is distributed during styling. The core needs to be sturdy enough to hold the barrel’s round form and, if you’re using a dryer, to conduct or distribute heat so you can smooth or set a curl efficiently. Leather isn’t suitable for this role because it can’t withstand high heat, would absorb moisture, wear poorly over time, and wouldn’t maintain a consistent barrel shape. In contrast, aluminum cores are lightweight and excellent at conducting heat, ceramic cores help distribute heat evenly for smoother results, and nylon can provide a durable, lightweight structure that still tolerates styling heat. So the material that doesn’t fit as a round brush core is leather.