Using both dish detergent and bleach to wash dishes is not a recommended practice. Dish detergent is specifically formulated for cleaning dishes and removing food particles, grease, and bacteria. On the other hand, bleach is a strong chemical disinfectant that can kill germs and bacteria. However, it is intended for use on non-porous surfaces and is generally not meant to be used directly on dishes.
Mixing bleach with other cleaning agents, including dish detergent, can lead to potentially dangerous chemical reactions and produce harmful fumes. Ingesting or coming into contact with such fumes can be harmful to health. Additionally, bleach can leave a strong residue on dishes, making them unsafe for eating.
It's essential to follow proper cleaning guidelines to ensure food safety and avoid any health risks. Washing dishes with warm water and dish detergent should be sufficient for daily cleaning. If you want to disinfect dishes, you can use a dishwasher with a hot water setting, which should be effective in killing most bacteria and germs.
If your late grandma used this method, it's possible that she might have been following practices that were more common or acceptable in her time, but it's important to note that current guidelines advise against using bleach directly on dishes.