Paintballs are highly engineered and formulated “frangible projectiles”. Which is just another way of saying – you can shoot them out of an airgun and they’ll break when they hit something.
Contrary to some popular myths, paintballs are not made out of –
plastic, glass, marbles, or anything else.
Paintballs have two components, the shell (the outer covering) and the fill (the ‘paint’, or more properly, ‘dye’).
Shells are made out of gelatin (essentially the same stuff as what jello is made out of) and a few other chemicals. Shell material is mixed, heated and then extruded into a thin sheet.
This sheet (actually two “ribbons”) are fed into a rotary encapsulation machine, which is also fed with the liquid dye. Inside the encapsulation machine, the two ribbons are drawn up against the paintball form (two hemispheres); dye is drawn in between the two halves at the same time and the machine presses everything together.
Newly formed paintballs are then processes through a tumbling and drying process before being packaged.
Everything used to make a paintball is biodegradable and non-toxic (some formulations are more degradeable than others). However, they can be toxic to dogs (and perhaps some other animals as well). You could eat them if you could stand the taste.
The differences between one ‘grade’ or brand of paintballs largely has to do with the quality consistency (higher standards for more expensive paintballs), the brittleness of the shell (very, very brittle paint is used in competition – guaranteeing a break on an opponent is extremely important) and the thickness/brightness of the fill (thick paint is also desirable for competition – it prevents wiping of hits).
Most new players will not be given much choice in the grade or brand of paintballs they get to use, and most paint supplied to newbies is generally of the “recreational” or “field” grades.
Rec/Field grade paintballs usually have a medium-thick, medium-bright fill and a shell that is fairly rugged.
Remember also that paintballs do not have a very long shelf life and their performance/condition can be affected by temperature and humidity.
(Recommended storage conditions for paintballs are 50% humidity, no direct sunlight and temperatures of between 55 and 75 degrees Fahrenheit.)
The following images will give you some idea of what shells and fills look like. (Note that these pictures are for illustrative purposes only.)
First image – various shells and fills.
Second image: “Drip tests” give some idea of the comparative “thickness” of different grades of fill.
Here’s a fifteen year old video from the Discovery Channel that shows the paintball manufacturing process: