Old Tom is one of the most confusing terms in the world of gin. There is little consensus as to what constitutes an Old Tom Gin. Here’s a little about what you should expect:
Old Tom Gins often used a variety of techniques to cover the flavor of their base spirit. The style dates back to a time proceeding the invention of the column still. Neutral Spirits were often not quiet neutral and had significant residual character, sometimes even unpleasant residual character. Old Tom Gin makers would try to cover that flavor. Often times an Old Tom Gin will have a malty, Holland-style base. Modern day Old Tom Gin feature high quality base spirits that have been distilled to modern day tastes.
They’re a bit sweet. Often times Old Tom Gins have sweetening added after distillation such as sugar; however, other distillers of Old Tom Gin use perceptually sweet botanicals such as licorice to impart a sweetness of sorts.
They’re sometimes aged. Gins used to be stored in barrels and these barrels were used over and over again. The character the barrel would add to the gin would depend on how new the barrels was and ultimately how fast that gin sold. Others rest their Old Tom Gin in a barrel because the Vanillin from oak adds a perceptual sweetness that can replace/augment other sweeteners or cover off notes in a base spirit.