For objects where the aesthetic properties of the object are more important it is possible to hide the recycling symbol until it is necessary to recycle the object. Two approaches were demonstrated here.
First, a drill bit handle was printed in ABS, with no visible recycling symbol on the exterior (such handles are popular in the 3-D printing community to ream out holes in RepRap part prints). The recycling symbol is in the center of the handle so that for about 50 layers only the symbol and the wall of the handle are present. Thus, when the handle is ready to be recycled it can be cracked open (as shown in Fig. 4) and the recycling symbol becomes clearly visible on the inside regardless of the location of the crack. This type of recycling symbol embedding—where the recycling symbol can become an integral (and potentially mechanically necessary) component of the part is difficult to impossible with traditional subtractive manufacturing techniques.