Which ever way you make spirit, it is absolutely essential to filter it before mixing it with any flavours. This is referred to as polishing your spirit. Brewers Choice currently stock the EZ Filter system and Column Filters to do this job, but any filtering system is better than none.
The best ingredient to filter your spirit is activated carbon. Activated carbon is used in many areas for filtration because of its effectiveness, from processing waste water to gold refining to making bourbon. Carbon is activated by passing oxidizing gases though it at extremely high temperatures. This produces carbon with millions of tiny pores that attract impurities in your spirit and holds onto them with “Pi Bonds”. This phenomenon is similar to how a balloon or comb charged with static electricity holds onto a piece of paper.
The activated carbon can then work as a type of “molecular sieve”, trapping the molecules which are larger than ethanol. They become trapped in the pores inside the carbon, and also by surface energies on the carbon. So it won’t remove methanol, but will remove larger molecules such as aldehydes, aminos and fusil oils (not good for your health and the taste of your spirit).
Diluting Your spirit First
Make sure that the alcohol strength is less than 50% before polishing it – the carbons will work more effectively. There are several reasons for this.
- The fusels do not dissolve as well into lower-percentage alcohol. If your spirit is diluted, and the fusels are therefore less dissolved, they are then more easily captured by the carbon.
- At the diluted ratio, the “nasties” are also diluted and become easier to collect.
- If the alcohol is too strong, the alcohol can attack the carbon and cause impurities to be leached out of the carbon into your spirit, making it dirtier.
Always use clean water to dilute as this reduces the amount of impurities the carbon has to remove. Distilled water is best, but clean tap water is satisfactory (and more economical).
Which Carbon to use?
After considerable research, Brewers Choice selected Pro-Carbon, the best carbon we could find. The properties of Pro-Clean Carbon are:
- Granulated (which is cheaper than pelletised carbon, but equally effective);
- Acid washed, so it is cleaner than standard granular carbon;
- pH stabilised, to prevent metallic aftertaste from regular activated granular carbon;
Our new Pro-Clean carbon is extremely efficient at capturing the typical fermentation by-products but without releasing any water soluble minerals that would taint the flavour of the product.
For more information on Pro-Carbon, read the full details in our Product Information section, here.
Speed of Filtering
When filtering, slower is better, for two reasons:
- Slower passage of the spirit past the carbon means more time for the carbon to attract the impurities out of the alcohol.
- The molecules trapped by the carbon are sometimes held fairly loosely. Filter too fast and the molecules can be washed off the carbon and back into your spirits.
For the column filter (and any filter system that uses loose carbon rather cartridges), do not start filtering immediately after filling the filter with unfiltered spirit. Give the filter column some time to fill up completely with spirit, filling all the air pockets. This will ensure that “channeling” does not occur (where the spirit flows down one channel) rather than getting exposed to all the carbon in the tube. After letting the filter fill with spirit, open your tap and allow your filter to drip at about 2 drops per second.
Make sure you always pass your polished spirit through a paper filter, as a last step. Many of the impurities are held by very fine carbon dust – and will still affect the flavour. Even spirit that appears crystal clear will leave a grey mark if run through a filter paper. Just use a filter paper or some tissue paper or filter wool in the bottom of the filter to trap the loaded dust. The column filters have some filter wool and a filter paper at the bottom of the filter for this reason.
Adding Carbon to the Wash
It is also a good idea to add activated carbon or Turbo Carbon to the wash at the beginning of fermentation. This helps to remove some of the unwanted impurities formed during fermentation. Make sure that you filter/decant off this carbon with the yeast, when you remove the wash. The best way to ensure the carbon is removed with the yeast at the completion of fermentation is to use Turbo Clear.