Sugar sweetens, preserves, helps the jelling action of pectin, and stops it from breaking down while the conserve is boiling. Since sugar also toughens fruit skins and slows down the initial release of pectin, it should be added only when the fruit is already softened, and should be fully dissolved before bringing the mixture to a boil. Coarser-grained sugar works best, since the larger crystals dissolve more quickly. The quantity of sugar to include is a matter of taste, but since it also affects the keeping qualities of the conserve, being aware of sugar’s preservation effect is important. Traditional jam and jelly recipes usually suggest equal quantities of sugar and fruit, and if properly potted and sealed, these will keep in a cool dark place for at least a year. In some jams, sugar may be reduced to as little as one-fifth of the weight of fruit. However, as the sugar level reduces, so does the keeping quality, and at very low levels the jam will need to be used quickly (within a few weeks) and kept refrigerated to prevent spoiling.