A mixer is provided that is configured for attachment to a power tool for mixing a viscous material, and includes a shaft defining a shaft axis, and a plurality of paddles attached to the shaft and extending radially from the shaft. All of the paddles have generally the same axial distance to the first end of the shaft, and the paddles are configured for rotation about the shaft axis in a direction of rotation. Each of the paddles has a general “S”-shape defined between a top end and a bottom end of the paddle, and between a leading surface and a trailing surface of the paddle.