Madeleine Berkhemer, an artist from the Netherlands, and van Oosten, a conservation scientist at the Cultural Heritage Agency of the Netherlands, are working jointly to find a way to prevent Berkhemer's art from deteriorating considerably after a long period of time. Yvonne R. Shashoua, a conservation scientist at the National Museum of Denmark, in Copenhagen, states that museum conservators are making such efforts to save plastic objects in their collections whose durability is unable to compete with the multiple-millennia- long stability of ancient bronze or stone artifacts. Conservators extend the lives of plastic objects by monitoring and modifying the environment around them. Objects made from polyvinyl chloride are protected by keeping them sealed in with their leachates in comparison with objects made with cellulose acetate and cellulose nitrate, which preserved by separating them from leachates to prevent further breakdown.