Making weapons-grade tear gas is dangerous, complicated and, in many places, illegal. No civilian would ever have legitimate use for such a chemical weapon. However, capsicum pepper spray is a popular self-defense tool used by civilians in many countries. Though not as toxic or as powerful as true tear gas, it’s not terribly difficult to make. You can keep this pepper spray in a regular spray bottle, though it can be kept in a pressurized bottle if you have the proper loading equipment.
Put on the gloves. The acids that make pepper spray effective can burn your skin in these concentrations.
Use the knife to slice the peppers into pieces half the size of your thumbnail. Throw away any stems.
Grind the peppers with your mortar and pestle until they form as fine a powder as possible. Crush and grind the seeds as well as the meat and skin.
Pour the pepper spice into the bowl with the white vinegar. Whisk until well stirred.
Store the mixture overnight in the refrigerator, letting the vinegar leach out as much of the spice as possible.
Add the water to the mixture. Whisk to stir until it's of even consistency.
Decant into your spray bottle. Store the remainder in a cool, dark place.
When it comes time to reload, shake your mixture thoroughly before adding more pepper spray to your bottle.
Instead of a mortar and pestle, you can grind the chili peppers in a coffee grinder. Be sure to wash it thoroughly afterwards, unless you like your coffee extra spicy.
Avoid touching your eyes or mucous membranes while preparing this pepper spray. As with any weapon, practice using your pepper spray before considering yourself ready to use it for self-defense. Check local laws concerning carrying pepper spray for self-defense.