While most actors can cry real tears, some assistance is often required to get realistic looking tears on camera. There are many eye drop solutions on the market, but it is possible to create a fake tear solution at home. Be sure to use pure ingredients to protect the eyes from any damage.
Sterilize all materials. Boil half the distilled water and use it to thoroughly rinse the measuring teaspoon, the stirring spoon and the inside of your container. Ideally, the container should be new or never have been used to store anything that could be dangerous to the eyes.
Pour the remaining liter of distilled water into your container. Do not allow any contaminants to get into the water.
Pour 1 teaspoon of cooking salt into the water. Cooking salt is better than table salt as it is more likely to be pure sodium chloride. If you have access to pure, chemical-grade sodium chloride, that is the safest ingredient to use.
Stir the solution until the salt is fully dissolved. Once there are no visible salt particles, seal the container. It is now ready to be applied with a sterile eyedropper to an actor's eyes before the scene that requires crying.
You can also purchase saline and glycerin solutions as eye drops.
A natural way to induce tears is to have the actor slice a fresh onion with a dull knife.
Remember that sterility is key so the solution will be safe for the eyes.