Question

How do fluorescent soap residues make clothing look “brighter and whiter” in outdoor light? Would this be effective in candlelight?

Short answer

Ultraviolet radiations are the primary cause.

Step-by-step solution

Definition of Ultraviolet Radiation

The two types of UV rays that make up the ultraviolet radiation that reaches the Earth's surface are known as UVA and UVB. Skin damage, accelerated ageing, melanoma, and other forms of skin cancer can all be brought on by it. The immune system and the eyes may both suffer as a result.

Fluorescent soap residues make clothing look “brighter and whiter” in outdoor light

Because outdoor light is primarily UV radiation from the sun, fluorescent soap residues make garments appear brighter and whiter in outdoor light. As a result, when fluorescent soap residues are exposed to UV light, clothing appears brighter and whiter.

However, because candles cannot emit ultraviolet light, garments cleaned with these soaps do not appear brighter or whiter.