Drain the liquid from the guava shells, measure, and pour into a small saucepan. Set the shells aside. Bring the guava juice to the boil and reduce to about ¼ pint. Add the lime juice. Dissolve the arrowroot in a little cold water, stir into the guava juice and cook over low heat, stirring constantly, until the mixture thickens lightly. Remove from the heat.
Spread a thin layer of this