This page describes how to knap an arrowhead out of a beer bottle bottom. This includes breaking a bottle and working with extremely sharp broken glass. The best part of the bottle to use is the bottom, because the glass tends to be thicker than the sides of the bottle, and much less curved. So when picking your bottle, pay special attention to the bottom.
Colored glass is better than clear glass .
Its very difficult to see what you are working on when you work clear glass. Wine bottles with big kick-ups are not good for knapping. Most bottles have some curvature to the bottom - its best to avoid noticeable concave bottomed bottles in favour of flatter bottoms. These lumps and bumps can be tricky to get rid of. Begin with a smaller beer bottle before you try a larger flat bottomed wine bottle .