Field marking dusts, or chalks, are generally created using ground calcium products. These limestone-based materials are located in deposits all over the continent but were formed differently depending on location. In the mountainous regions along the east and west coasts, the limestone deposits were subjected to tremendous heat and pressure during formation. The result is a metamorphosed limestone commonly known as marble. Limestone deposits formed between the two mountainous regions, in the central part of the continent, usually will be softer material formed by a sedimentary process.

Differences in particle size, shape and hardness of these two different materials dictates the brightness and flow properties of these ground materials. One common denominator with these products is when they are ground, the particles all have fairly angular surfaces.

It is this angularity that causes the materials to interlock and bind up in your chalker’s hopper. The result is bridging and that means a reduced flow through the dry line marker. When the chalking material is poured into the hopper, air is also introduced and that fluffs the material a bit so it flows better. As the marking machine is moved along, the vibration slowly settles and out goes the air the fluff… and that’s when the particles begin their interlocking. The particles become tighter and tighter and that compaction in the hopper is why bridging occurs. This can explain why your lines are inconsistent and there are noticeable gaps or thin spots. That’s not good.