Although oil paint remains the medium of choice for many artists, who value its great versatility, conservators prefer to use the more recently developed synthetic resins when restoring oil paintings. This preference has to do with the difference in the type of binding medium that constitutes each of these paints. Paint is a mixture of pigments (finely ground powders that provide color) and a binding medium or binder (a liquid component that binds the pigments and converts into a transparent solid film upon drying.) Oil, a natural material, is the binder in oil paints; synthetic resin is the binder used by most conservators today. The most widely used oil for paints and varnishes is linseed oil, which is extracted from the flax plant. Other oils such as walnut, poppy and sunflower are also used. These oils, particularly linseed, have a tendency to yellow with age at a faster rate than synthetic resin binders. Synthetic resins are not only less susceptible to yellowing but also dry faster than oil paints. These synthetics allow conservators to work faster and ensure that their conservation treatments will last for many years without discoloring. Additionally, layers of oil paint cross-link--a molecular bonding process that causes a hardening of the paint film over time and a chemical resistance to many solvents. Given that the cardinal principle of conservation today is reversibility, synthetic resins are preferable for inpainting because they do not crosslink and are, therefore, more easily removable. Oil paint can be almost impossible to remove over time, making future restorations very difficult. Inpainting with oil paint can also produce craquelure— fine spider-web cracks on the paint surface that result from overlapping two or more oil films. The first layer will crack if it is not allowed enough time (typically weeks) to dry, and these cracks can be seen through the top film layer. Though it is a common feature on old master paintings and an inevitable result of the artist’s technique, craquelure is not a desirable outcome when inpainting, as conservators seek to preserve as much of the original appearance of the painting as possible. Synthetic resins, however, do not cause craquelure when properly applied. Although oil paints were often used to restore oil paintings in the past, conservators today strive to replace these restorations with synthetic resins, which not only offer the advantages of rapid drying and reduced yellowing with age but are also more stable and reversible. Lowy continues to observe the highest standards of conservation as ongoing research aids in the development of new and better materials for painting restoration.