A dual spring includes a pair of conically-shaped spring sections, which are joined at a common fulcrum. CHME esters are particularly suited to thickening or structuring a water-immiscible liquid, for example, a phase in a cosmetic formulation, such as antiperspirant or deodorant formulations, eg water in oil emulsions and especially translucent ones. Thus, it is possible to reduce reliably wear and damage of the pen tip 2 which results from engraving a hard workpiece, and to prolong the useful life of the pen tip 2, so that the durability and the reliability of the apparatus are improved. The lip is substantially normal to the shelf surface and the shelf surface is at an angle relative to the back wall.