Methods and apparatus for providing a leak-proof seal for two-piece capsules containing oil-based liquids or other compositions by a two-stage process. The capsule cap and capsule body are combined by a nitrogen purge instant bonding (NPIB) system. An overlay medium is applied to selected portions of the capsule, including near the seam formed by the interconnection of the capsule cap and capsule body to provide a substantially leak-proof seal. The overlay medium is made from materials that make up the capsule cap and capsule body, including gelatin, starch, cellulose or polysaccharides, among others, which are dispersed in a hydro-alcoholic, aqueous or organic solution. The overlay medium includes additives to impart desired qualities to the capsule and include taste-enhancers, taste-maskers, odor-enhancers and odor-maskers. The additives may include color additives, aroma additives and taste additives.
