ANDREW LAMBERT PHOTOGRAPHY / SCIENCE PHOTO LIBRARY ANDREW LAMBERT PHOTOGRAPHY / SCIENCE PHOTO LIBRARY
Bleach with universal indicator added. Universal indicator changes colour depending on whether it has been added to an acid or an alkali. Bleach is a strong alkali, and in alkaline solutions, universal indicator turns a colour between purple (strong alkali) and green (weak alkali). In acidic solutions, it turns between yellow-orange (weak acid) and red (strong acid).
Model release not required. Property release not required.