Coating vegetables, meats or fruit tarts with a syrupy glaze adds shimmer and flavor to each bite, unless the glaze is too thin to cling to the food. The techniques for thickening a glaze are basically the same, regardless of whether the sauce is sweet or savory. Concentrate the mixture or add a thickening agent to it -- or use both techniques if you're after a really sumptuous sauce.
Concentrate the Glaze
Cooking a glaze in a saucepan over medium heat evaporates off excess liquid and leaves a sauce with syrupy texture and concentrated flavor. Stir the mixture often and remove it from the heat as soon as you're happy with its thickness. Reduce a mixture of balsamic or apple cider vinegar and honey in this way to make a simple glaze for pork or vegetables.
Adding any type of starch to a glaze will thicken it quickly. For every 1 cup of glaze, mix together 1 tablespoon each of cornstarch and cool water or other cooking liquid. Whisk this mixture into the glaze and simmer it, stirring often, until the sauce thickens. Use the same technique with tapioca starch or arrowroot powder for a super glossy glaze. Heat the glaze only as long as you need to for it to thicken because starch starts to break down when overcooked. You may also stir confectioner's sugar into a sweet glaze to thicken it quickly.