The congener of “tar” is parts of the “burnt” sub category as part of the “peaty” head category.
“Burnt” is a congener that is chemically linked to a lot of chemicals. For an overview one can look at this page on the “the goods cents company” website. This website does not have a “peaty” congener, but it does have one for “smoky”.
Tar should not be confused with Bitumen or Asphalt. These are different materials.
Tar is a product made from natural products like Birch wood, coal or indeed peat. The processes to make tar are described better in other sources but it comes down to the breaking down of long carbon chains that are formed in organic materials into smaller molecules or shorter Carbon Chains like hydrocarbons and carbon. Some of the results might be solids at room temperature. When heated it would turn into a liquid.
In the past tar was used to waterproof sails, ship decks, leather coats etc. Apparently also medicinal and uses in Soap and Chewing gum are known.
Since tar is, as far as I know, not used to waterproof whisky casks I cannot see a direct connection to the casks.
I personally have not drunk Tar, so I presume this is a nasal congener.
The Birch Tar Wikipedia site says some of the phenols in Birch Tar are compounded of phenols such as guaiacol, cresol, xylenol and creosol. These are, for me, naturally connected to the smoky smell of a whisky. So it makes sense that Tar is a general descriptor.
Peat Tar is a liquid product of the distillation of peat. Peat tar is a complex mixture of many chemical compounds, such as monohydric and polyhydric phenols and their esters, paraffins, waxes, fatty acids, alcohols, aldehydes, ketones, nitrogen bases, and neutral oils. Peat tar is obtained as a by-product of the gasification and coking of lump and milled peat.
On Youtube some video’s are highly informative and helped me a lot in understanding both Pine Tar and Birch Tar.
First a Video on Pine Tar:
Second a Video on Genereal uses of Tar.
Third a video on Birch Tar
The one process in which I can imagine Tar would be produced as a by-product would be in the malting of the barley. If coal or peat is used in a way where a fully oxygenised fire would just burn the peat I can imagine that some of the malting fires based on peat or coal might be less efficient, to produce the smoke, fires that would result in a type of destructive distillation as seen in the video’s.
If this is so then the malting ovens could be layered with some tar that would burn again at the next fire. Since I have never at a malting I can assume that some of the distilleries that still do their own malting would know if Tar would be a byproduct of the drying of the malt!
Do any of you know?
So to conclude: Tar seems to be made of Carbon based molecules like the char of the barrel. But is also contains phenols that come from organic materials being broken down in processes where the long chain molecules are cracked. These phenols will transfer thru the process.
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