Whisky Off Notes: How to Recognise Common Faults

Damp cardboard, rotten eggs, a farmyard smell: whisky can carry aromas far removed from the expected pleasures of the glass.[3][5][8][10] Even “cork taint” can arrive through warehouse timber, pallets or packaging rather than the stopper.[5] The task is to recognise what you smell, judge its intensity and decide whether it overwhelms the whisky. An unfamiliar aroma, a trace of sulphur or cloudiness after adding water does not automatically mean a fault.[3][11]

In short

• Cork taint can reach whisky through materials other than the stopper.[5]
• For suspected TCA, researchers recommend dilution to 20% ABV and prompt nosing.[5]
• Sulphur compounds can contribute body and complexity at low levels.[3]

Recognise the note before naming the fault

“Wet cardboard” describes a smell. “Cork taint” suggests its cause. Keeping those two things separate makes an assessment clearer from the outset. The same distinction matters with sulphur: several compounds produce different aromas, and their effect depends on concentration.[3][5] Use the whisky flavour wheel to find precise language rather than treating every unfamiliar note as a defect.

Laboratory reference descriptions help distinguish aromas that might otherwise all be called “sulphury”. They give you a vocabulary for the glass, rather than a chemical identification of its contents.[3] Start with the closest sensory match and judge how strongly it comes through.

Rotten egg points towards hydrogen sulphide; rotten cabbage towards methanethiol. Dimethyl sulphide, usually shortened to DMS, is associated with cooked sweet corn, cooked vegetables and cooked tomato. Dimethyl trisulphide, or DMTS, has been described as onion-like and meaty.[3] Trade descriptions also include struck matches, gassy and rubbery characters for thiols.[9]

When sulphur adds character, and when it dominates

At low levels, sulphur volatiles can give whisky body, heaviness and complexity. At high levels, they can become unpleasant.[3] The useful question is therefore not simply whether sulphur is present, but what it does to the whisky. Is it a background accent or the dominant impression? Describe what it contributes to the overall aroma, or what it obscures.

The published thresholds reveal how much the compound matters. One reported threshold for DMS is 5 micrograms per litre in 20% ethanol; for DMTS it is 0.05 micrograms per litre in the same medium.[3] These reference measurements apply to diluted ethanol, not universally to bottled whisky, and cannot be used to calculate a concentration from a smell.

Copper contact during distillation can reduce sulphury aromas, including those associated with DMTS. Harrison and colleagues found that copper was more effective in some parts of the still than others.[4] Fermentation management matters too. WSET's account links increased sulphur production to yeast stressed by heat, excess sugar or insufficient nutrients.[12]

Maturation changes these compounds at different rates. The review reports that DMS falls markedly during maturation, DMDS gradually and DMTS slowly.[3] Sulphur is a family of aromas, not one smell following one path through the cask. Naming the particular character and recording its strength tells a reader more than a blanket judgement about sulphur.

Cork taint: damp cardboard and suppressed aroma

Whisky can be corked. Above its detection threshold, TCA, short for 2,4,6-trichloroanisole, can produce musty, stale, damp-cardboard notes.[5] The trade reference Is there such a thing as corked whisky? describes wet newspaper or cardboard. It also notes that whisky's strength and aromatic intensity can make the taint harder to spot than in wine.[6]

The stopper is only one possible source. Baxter, Réveillé and Conner identify casks, cardboard packaging, pallets and wood used in warehouse construction as routes into whisky.[5] “Cork taint” is therefore a broader problem than its name suggests. Describe the damp-cardboard impression carefully before attributing it to a particular material.

Tasters also differ in sensitivity. Earlier unpublished SWRI work reported in the 2024 paper involved 217 panellists and found an average threshold of 4.40 nanograms per litre in 20% ABV neutral spirit. In whisky, the expert panel's thresholds ranged from 2 to 33 nanograms per litre, depending on the whisky.[5] Two attentive tasters can disagree about the same glass.

The whisky itself can make TCA harder to detect. The researchers found that congeners, the flavour compounds accompanying ethanol, masked its mustiness compared with neutral spirit. Increasing ethanol also left less TCA available in the headspace, the air above the liquid. The drop was particularly sharp between 30% and 40% ABV.[5]

Farmyard, feinty and rancid notes

Earthy, leathery and sometimes meaty aromas appear in trade descriptions of “feinty” character. Those accounts connect it with a late spirit cut, the point at which the distiller stops collecting the middle fraction.[8] The language overlaps with descriptions of other whisky aromas, however, so leather alone does not establish a faulty cut.

The Scotch Malt Whisky Society's Unfiltered also links the breakdown of fatty acids and aldehydes with rancid or musty notes.[8] This is where a precise description earns its place. “Rancid”, “damp cardboard” and “earthy” describe different impressions. Choose the closest match rather than gathering several negative words around a smell you have not yet pinned down.

Butyric character, described as farmyard, is normally linked to poor distillery hygiene and treated as an off-note by distillers and blenders, according to Nicholas Morgan's trade account.[10] Yet maturation can change the outcome. The same article quotes Diageo's Craig Wilson explaining that butyric and acetic notes can become fruity ethyl butyrate and ethyl acetate during maturation. What smells unwelcome in developing spirit need not define the finished whisky.

A focused check for suspected TCA

For suspected damp-cardboard taint, full strength is not necessarily the best place to look. Baxter, Réveillé and Conner recommend dilution to 20% ABV, prompt assessment by nose and, where possible, chilling to 5°C (41°F).[5] Their method targets TCA specifically, rather than serving as a general test for every whisky fault.

1. Measure a small sample. Use a plain nosing glass and measure 5 ml of whisky. Work from the labelled ABV, since bottles differ in strength. For general smelling technique, see nosing whisky.
2. Dilute to 20% ABV. For a 5 ml sample at 40% ABV, add 5 ml of water; for 5 ml at 60% ABV, add 10 ml of water. These quantities are dilution calculations applying the study's target strength, rather than separate experimental findings.[5]
3. Nose promptly. Assess the diluted sample without a prescribed resting period. If practical, chill it to 5°C (41°F), as the researchers recommend. Look specifically for mustiness, stale cardboard or damp newspaper. A general reduction in aromatic intensity does not establish taint.[5][6]
4. Record what changed. “Damp cardboard becomes clearer after dilution” captures an observation. “The cork contaminated the whisky” assigns a cause that the aroma alone cannot establish. Use writing tasting notes to keep the descriptor, its intensity and your interpretation separate. You do not need to swallow the sample.

If you taste as well as nose, spitting is normal and nobody need finish a glass. Keep servings small and measured, with water, food and breaks available. People who are pregnant or trying to conceive, taking medicines that interact with alcohol, living with conditions made worse by alcohol, recovering from alcohol dependence or driving should not drink. See the Responsible Drinking page.

Cloudiness is not evidence of spoilage

Water or ice can turn a clear whisky hazy without introducing a fault. The Scotch whisky technical file explains that long-chain esters can come out of solution at low temperatures or after dilution.[11] This is a physical change: cloudiness alone does not mean the whisky has gone off. Keep that visual change separate from the damp-cardboard aroma associated with TCA.[5][11]

Make the description useful to someone else

A useful fault note gives another reader a specific aroma to recognise. Replace “bad sulphur” with the closest description: rotten egg, cooked cabbage, struck match or onion-like meatiness. If you write “musty”, make clear whether you mean damp cardboard, earthiness or leather. The published descriptors supply a shared vocabulary, while chemical identification remains a different task.[3][5][8][9]

Preference belongs alongside description, not in its place. “The meaty note dominates for me” says more than a declaration that all meaty whisky is faulty. Low-level sulphur can contribute body and complexity, while TCA detection varies with both the whisky and the assessor.[3][5] Name the unwelcome aroma, say how strong it is and explain its effect on the glass. That gives the reader a firm assessment without assigning a cause the smell alone cannot reveal.

Where to go next

• How to Taste Whisky: The Complete Guide: a framework for assessing the whole glass before isolating one note.
• Nosing Whisky: How to Smell It Properly: technique for a focused aroma assessment.
• Writing Tasting Notes: ways to separate observation, intensity and interpretation.

Sources

[3] Wanikawa and Sugimoto. A Narrative Review of Sulfur Compounds in Whisk(e)y. Molecules, publication year not supplied in the fact sheet.
https://pmc.ncbi.nlm.nih.gov/articles/PMC8911989/

[4] Harrison, Fagnen, Jack and Brosnan. The Impact of Copper in Different Parts of Malt Whisky Pot Stills on New Make Spirit Composition and Aroma. Journal of the Institute of Brewing, volume 117, 2011. Bibliographic record supplied through Semantic Scholar.
https://www.semanticscholar.org/paper/The-Impact-of-Copper-in-Different-Parts-of-Malt-Pot-Harrison-Fagnen/5fa7c97527d6a05410f6496549b2c358e167d1c0

[5] Baxter, Réveillé and Conner. Guidelines to optimise the sensory detection of 2,4,6-trichloroanisole in neutral spirit and whisky. Journal of the Institute of Brewing, 2024.
https://jib.cibd.org.uk/index.php/jib/article/download/51/75/69

[6] ScotchWhisky.com, Ask the Professor. Is there such a thing as corked whisky? Trade article, publication date not supplied in the fact sheet.
https://scotchwhisky.com/magazine/ask-the-professor/10349/is-there-such-a-thing-as-corked-whisky/

[8] Scotch Malt Whisky Society, Unfiltered. Beyond the comfort zone. Trade article, publication date not supplied in the fact sheet.
https://smws.com/unfiltered/adventures-in-whisky-beyond-the-comfort-zone

[9] Dave Waddell, ScotchWhisky.com. What's wrong with sulphur in whisky? Trade commentary, publication date not supplied in the fact sheet.
https://scotchwhisky.com/magazine/opinion-debate/the-way-i-see-it/6740/there-s-nothing-wrong-with-sulphur/

[10] Nicholas Morgan, Master of Malt blog. Who Got Da Funk? Trade article, publication date not supplied in the fact sheet.
https://www.masterofmalt.com/blog/post/who-got-da-funk/

[11] UK Government. Technical File for Scotch Whisky. June 2019 edition.
https://assets.publishing.service.gov.uk/media/5fd36667e90e07662ed92c85/Scotch_Whisky_Technical_File_-_June_2019.pdf

[12] Anthony Gladman, WSET. How important is copper, really? Trade article, publication date not supplied in the fact sheet.
https://www.wsetglobal.com/news-insights/insight-opinion/how-important-is-copper-really/

This article is desk research based on the site's verified fact sheet TOP-A487, distinguishing research findings from attributed trade accounts; no site tasting or experimental test is claimed.

Last checked: November 2026