Hydroquinone 1% solution is a weakly concentrated solution of the organic compound hydroquinone. Hydroquinone is an aromatic with the chemical formula C6H4(OH)2. It is a type of phenol and has two hydroxyl groups (-OH) directly opposite each other on a benzene ring.

In photography, hydroquinone is often used as a reducing agent in developer solutions because it has a strong reducing effect. It is known to produce dense black areas in black and white negatives and prints.

In biology and medicine, hydroquinone is used as an antioxidant and as an inhibitor of polymerizations and biological oxidations. It is also used in microscopy as a reducing agent in staining techniques.

So a 1% hydroquinone solution would be one containing 1 gram of hydroquinone in 100 ml of solvent. This concentration would be rather weak and may be suitable for applications where a strong reducing effect is not necessary or desired.