North American Whiskies 

Law > Bourbon, Straight Whisky 

Bourbon and Straight Whisky are defined in the US Federal law. 


Required grains - minimum 51% corn

Distillation - maximum of 80%abv / 160 proof

Maturation - stored at a maximum of 62.5%abv / 125 proof in new charred oak containers 

Finishing - bottled at minimum 40%abv, can be a mix of spirits of different ages that conform to the above requirements.

Labelling requirements - no minimum ageing. Age statements are only mandatory when the youngest spirit in the blend is less than 4 years old. All age statements are determined by the youngest spirit in the blend.

Straight Whisky

Bourbon is 1 of the 6 types that may use the term "straight"

others > rye, wheat, malt, rye malt and corn

Maturation - a whisky must have been aged for at least 2 years in oak

Finishing - no colouring or flavouring may be to added to a straight whiskey

Bourbon Production 

  • vast majority is made in the state of Kentucky

  • bourbon can be made anywhere in the USA

  • flavour profile > full-bodied, sweet, punchy, rich with layers of vanilla, coconut, citrus, toffee and spice

Raw Materials 

  • minimum 51% corn > gives a soft sweetness

  • + a selection of small grains, eg. rye, wheat and malted barley 

  • rye > gives bourbon its attack, aromatic, lemon and slightly dusty when young. Rye in bourbon can be detected from the middle of the palate, acidic and slightly oily quality begins to bite.

  • wheat > gentle, rounded quality and notes of honey

  • malted barley > enzymes and biscuity sweetness 

Processing the raw materials 

Mash Bill 

  • % of small in the mash bill makes an important contribution to the overall style 

  • to create variety in the production process, use a number of different mash bills. Typically 2-3


Sugar solution is known as "mash"

  • corn is ground into fine meal and mixed with water

  • cooked at a high temperature in order to hydrolyse the starch

  • both open and pressure cookers are used 

  • corn mash cools slightly before the other grains are added (rye or wheat)

  • other grains starches hydrolyse

  • once cooked the temperature is dropped to less than 65c 

  • malted barley is added in order to convert all the starch into sugar

  • some distiller use cultured enzymes to assist with the conversion


  • stainless steel or wood vessels 

  • lasts for 3 days 

  • 2 defining features > Backset/sour mashing and Yeast

Backset/ sour mashing 

Backset: the acidic liquid residue left at the foot of the beer still, Bourbon and Tennessee whiskey distillers need to use backset because they use hard, alkaline water, backset changes the pH, making it slightly more acidic.

Benefits of adding backset​

  • yeast propagation

  • lowers risk of bacterial infection

  • evens out character between batches 

  • the fermenter is filled with mash and backset

  • backset can also be added to the cooking (mashing process) this is known as "sour mashing"

  • only some Kentucky/Tennessee distillers use the term "sour mashing" all use the process 

  • backset makes up 20-30% of the fermenter > depending on mash bill, size of fermenter and house style

  • too much backset > too acidic and lose of flavour

  • too little backset > too thick, problems with solids during distillation 


  • guarded strain strains 

  • major flavour contributor 

  • cultured yeast to produce specific flavours 

  • one yeast strains for all mash bills OR multiple yeast strains paired to a particular mash bill

Image below - empty mash tun


All bourbon, except 1 (Labrot & Grahman) are double distilled 

Law - maximum 80%abv, most collect well below

  • 1st distillation > single column still (beer still). Column is cheaper and more efficient

  • column still is made from copper or stainless steel with copper parts

  • aim is to separate the volatiles from much of the water

  • mash enters at the top of the beer still and is met with steam pumped in at the base of the still

  • result is a distillate "low wines" 50-60%abv

  • the backset is collected from the bottom of the column and used in the mash tun and/or fermenter 


2nd distillation > type of pot still known as a "doubler" or "thumper"



  • simple design of a pot still, do not operate in the same was as Cognac/Scotch

  • has to be heated 

  • low wines coming off the beer still are condensed

  • the liquid is pumped continuously into the doubler

  • aim > further refine congeners 

  • slight rise in alcohol level between low wines and the final spirit 


  • type of doubler 

  • vapours coming off the beer still are NOT condensed

  • they go directly into the thumper

  • the heat of the vapours powers distillation in the thumper

  • the bubbling of the vapours makes a loud thumping sound 

Distillers will collect the new make spirit "white dog" anywhere between 56%abv to 65%abv depending on their house style 

Image below - Beer still + Doubler 


  • enter barrel at a maximum of 62.5%abv

  • alcohol levels rise during maturation in Kentucky due to the hot and dry weather 

200L new charred white american oak barrels 

  • high colour extractives

  • gives the spirits all of its colour 

  • vanilla, coconut, pine

  • in time > sweet spices, chocolate, tobacco, cherry

  • heavy char > thin layer of charcoal, removes aggressive notes in the new make spirit

Kentucky climate

  • hot summers, cold winters 

  • high temperature > whisky to expand more into the wood

  • marked temperature differences between top and bottom floors, whisky within the same warehouse can take all very different characteristics

  • barrels are stored in wooden-framed metal clad houses OR brick warehouses

  • temperature can be controlled by opening/closing windows 

  • small number of warehouses have electronic temperature control 

Blending and Finishing 

  • barrels stored in particular location in a warehouse will always result in a similar style of quality 

  • bourbon will be made from a blend of barrels from different floors and warehouses

  • blenders will always know the location of the best barrels "honey barrels" some producers has begun to release small batches or single barrel bourbons 

  • reduce to bottling strength with water

  • most are sold as straight whiskey > min 2 years aging 

  • no caramel for colouring adjusting is permitted for straight whisky

Image below - rack house 

Tennessee Whiskey 

  • must be aged and made in Tennessee 

  • prior to ageing the spirit must be filtered through maple charcoal

  • all other requirements are identical to bourbon

  • mash bill, min 51% corn

  • backset/sour mashing

  • distillation to a maximum of 80%

  • enter barrels at maximum 62.5%

  • 200L white american oak barrel, heavily charred

  • minimum bottling 40%

  • normally sold as straight whiskey, min 2 years and no other additions can be made except water for dilution.

  • production is dominated by one producer - Jack Daniels 

One important difference > Lincoln County Process

  • after distillation the white dog is slowly filtered through a 3m deep bed of sugar maple charcoal

  • white dog moves slowly through the charcoal, drop by drop at a pace only dictated by gravity

  • JD - charcoal and achieve in days what barrels take years to accomplish

  • the charcoal used in this process is only able to extract a small % of the flavours and some of the harshness from the white dog

  • gives a smoother mouth-feel

  • the charcoal is made from by burning hard pallets made from sugar maple 

  • the pallets are douse with whiskey and set a light

  • the charcoal pellets once cool are then collected to form the bed of charcoal

Image below - Charcoal mellowing vat at JD

Rye Whiskey & other American Whiskey

Rye Whiskey

Regulations are identical to that of bourbon EXCEPT the mash bill, production is similar too

  • 51% Rye 

  • rye - spicy edge, characterful intensity

  • revival - among bartenders in particular 

Other American Whiskey

Blended whiskey - blend of minimum 20% straight whiskey, remained being whiskey and HRS

  • does not have significant presence outside of US

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