Whisky · Explainer
What do first fill and refill mean for a whisky cask?
First fill means that whisky goes for the first time into a cask that previously held bourbon, sherry or wine. Every subsequent fill is called refill. A cask lasts three to four fills and gives off less colour and wood flavour each time. In Scotland it must be oak, no more than 700 litres.
In brief
The key figures
| First fill | the first filling with whisky of a cask that previously held another drink |
|---|---|
| Refill | every subsequent filling of the same cask, also known as second or third fill |
| Lifespan | three to four fills per cask, together up to about fifty years of service |
| Burning out | char 1 to char 4; the charred layer is about 2 to 4 millimetres thick |
| Rejuvenation | shaved and re-charred, usually at most twice per cask |
| Cask material | oak, mandatory under the Scotch Whisky Regulations 2009 |
| Maximum volume | 700 litres |
| Ageing | at least 3 years in Scotland, bottling at a minimum of 40 percent |
What is the difference between first fill and refill?
A first fill is the first filling with Scotch whisky of a cask that previously held bourbon, sherry, wine or beer. Every subsequent filling is called a refill.
The count only starts with the whisky. A bourbon barrel that has held bourbon for four years and is then filled with Scotch whisky for the first time is a first fill bourbon barrel. If whisky goes in again after it has been emptied, you speak of second fill or simply refill.
Why does a first fill give colour and flavour faster?
The wood is then still richest in soluble substances. Vanillin, wood sugars and coloring dissolve fastest at the first fill; with each subsequent fill there is less left.
Research into Scotch whisky in casks with varied histories showed measurable differences in the substances that come out of the wood, already within the first three years. According to Whisky Magazine, a first fill bourbon cask yields more vanilla, sweetness and colour than a second fill of the same cask.
How often can you fill a whisky cask?
Three to four times, reports Whisky Magazine, which together can yield about fifty years of service. After that the wood gives off too little to still impart character.
A spent cask is called a tired cask in practice. Such casks are still used for long maturation where little wood influence is wanted, or they go to the cooperage for treatment.
What is rejuvenation, or re-charring?
An exhausted cask is shaved on the inside and re-charred, exposing fresh wood again. Two treatments is usually the maximum, with at most two extra fills per treatment.
The charring itself takes about three to four minutes with gas burners. The charred layer is about two to four millimetres thick, with beneath it another layer in which the wood sugars have caramelised. According to Whisky Magazine, such a cask at best reaches the status of semi first fill.
What requirements does the law set for the cask?
Scotch whisky may only mature in oak casks of at most 700 litres, in Scotland, for at least three years. At bottling a lower limit of 40 percent alcohol applies.
The Scotch Whisky Association adds which casks are permitted: new oak, or previously used for still wine, fortified wine, beer or spirits. Excluded are casks that held stone fruit, beer to which fruit, flavouring or sweetener was added after fermentation, and spirits to which that was done after distillation.
From the shop in Bathmen
Bourbon-matured whisky in the shop in Bathmen
The shop in Bathmen stocks 75 whiskies matured in bourbon casks, from 52 different brands from 10 countries. The alcohol percentage ranges from 40% to 63.2%.
- Auchentoshan American Oak 40% · 70 cl · Scotland
- Ballechin 12 Years Old 2011 Straight From The Cask Bourbon 53% · 50 cl · Scotland
- Ballechin 2011 10 Years Old Straight From The Cask Bourbon 59% · 50 cl · Scotland
- BALLECHIN SFTC Bourbon Cask 10 years old 58.4% · 50 cl · Scotland
- Belgian Owl Single Malt Passion Bourbon Cask 47 months 46% · 50 cl · Belgium
- Bimber Ex-Bourbon Oak Casks 51.2% · 70 cl · England
- Bimber Single Malt Ex-Bourbon Oak Casks 52.2% · 70 cl · England
- Booker's Bourbon 7 Years + 1 Month + 11 Days 63.2% · 70 cl · Scotland
- BUS Bourbon Aged Single Malt 46% · 70 cl · Netherlands
- Bushmills 15 Years Old Bourbon Cask 46% · 70 cl · Ireland
Related questions
What does NAS mean for whisky?What does non-chill filtered mean for whisky?What does on the rocks mean for whisky?
Short answer
Short answers to related questions
- Is a refill cask worse than a first fill?
- No, just different. A refill gives off less wood and colour, so the character of the distillate remains more clearly recognisable.
- Does the previous content count as a fill?
- No. The counting starts with the first fill of whisky. The bourbon or sherry before it does not count.
- May a gin or cider cask be used for Scotch?
- No. Maturation is not part of the usual production of gin, and cider is not beer, wine or spirit.
- Does the 700-litre limit apply everywhere?
- The limit is in the Scottish regulations and also in the Japanese standard for Japanese whisky. Other countries have their own rules.
The reasoning
Sources
- The Scotch Whisky Regulations 2009, regulation 3, legislation.gov.uk (accessed 4 September 2026)
- Guidance on allowable casks for maturation, Scotch Whisky Association (accessed 4 September 2026)
- Lets do the char char, Whisky Magazine (accessed 4 September 2026)
- Effects on Scotch whisky composition and flavour of maturation in oak casks with varying histories, International Journal of Food Science and Technology (accessed 4 September 2026)
Deze pagina is geschreven en gecontroleerd door ’t Bockje Bathmen, slijterij aan de Brink 2 in Bathmen. Laatst bijgewerkt op 1 november 2026.
Verkoop van alcohol onder de 18 jaar is verboden. NIX18.