Polishing Neutral Spirit


Summary
Soaking neutral alcohol with activated carbon for a week (or even months) will help remove some of the off-flavors - this is known as "polishing" the spirit.

The spirit should be diluted to 30-50% before polishing.

Don't polish spirits that you want to keep the flavor of (eg whisky or schnapps).


If you are making NEUTRAL alcohol, make sure it is polished using activated carbon or better (see below). Soak it for at least a week (and up to a couple of months) to remove any aldehydes, aminos and fusil oils that could be present. I use about 1 cup of carbon to 4-5L of spirit. This will take out the rough edge usually associated with typical moonshine, and leave vodka's clean, tasteless & odourless, ready for flavoring.

If you DON'T want vodka, then DON'T use carbon.

The carbon works by being a type of "molecular seive", 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 only larger molecules (eg the fusels). Likewise, the trapped molecules are sometimes held fairly loosely to it, so if you try to filter too fast, they can be washed off the carbon and back into your spirits.

Make sure that you always pass your polished spirit through a paper filter. Many of the impurities are held by very fine carbon dust - and will still affect the flavor. If you pass even crystal clear polished spirit through a paper filter, you will notice that it becomes grey or black. You'll notice the cleaner flavor too. It doesnt take much - just a littl bit of tissue paper or cotton wool in the bottom of a filter, and you'l trap that loaded dust.

If you're looking to buy carbon, see Brewhaus.

Grant writes ...
    activated carbon acts in three ways:

    Adsorption - relying on electrostatic Van der Walls forces. This attractive "force" forms relatively weak bonds between the carbon and adsorbate. In theory activated carbon could release or desorb what it removed at some point, but from practical experience desorption rarely occurs.

    Absorption - refers to the diffusion of a gas or compound into the porous network where a chemical reaction or physical entrapment take place. Ozone for example is absorbed into activated carbon where it oxidizes a portion of the carbon's surface. Ozone (O3) is reduced to oxygen (O2) thus "detoxified". Ozone does not accumulate or build-up in the carbon structure.

    Chemisorption - an irreversible chemical bond between the carbon surface and the adsorbate. Pollutants are tightly bound to the sorbent.

    The filtering of alcohol primarily involves the removal of organics via adsorption. After the activated carbon has reached exhaustion and all the adsorptive sites are filled, it can be regenerated. Chemisorption is associated with the removal of inorganic chemicals and the carbon used to remove these compounds is generally not regenerated.
to which Mike Nixon adds ..
    Adsorption is primarily an electrostatic phenomenon and chemical bonds play no part in it. The porous nature of the carbon is induced in order to increase the surface area available, a typical value often quoted (and true) is approximately one football field area per cubic centimeter of carbon. This process of inducing porosity is what is meant by the term "activation". Geometry also plays a part in this, enhancing the weak electrostatic attraction for certain sizes and shapes of molecules in a manner similar to that used by enzymes which have shaped "pockets". In this manner, materials can be processed to selectively adsorb some molecules better than others, as in respirators. Carbon that has not been treated in this way will still adsorb molecules but, for practical purposes, the effect will be insignificant if the surface area has not been increased. Adsorbed molecules held on the surfaces both inside and outside of the carbon may be released by heat and subsequent vaporisation. Please do not confuse rinsing new carbon to get rid of salts etc before initial use with heating after use to release adsorbed molecules.

    Specifically, we are interested in removing compounds that have taste or odor and which, like those that contribute color, tend to bind strongly. With these, the only bonding is by weak Van der Waals forces. There is no significant redistribution of electron density in either the molecule or at the substrate surface, and subsequent release of the molecules by heating is easy. Heating in an oven to 160 deg C is quite sufficient to clean used carbon to the extent that it can be used again, particularly when the carbon is first soaked in water to provide active flushing with steam as it boils. Of course, this will not release all the adsorbed molecules … heating to a much higher temperature in an inert atmosphere is needed to do that thoroughly … but 90+% efficiency is good enough for all practical purposes, and has been used as a cost-effective recovery process by sugar refineries ever since 'white' sugar was processed.

    Wet activated carbon primarily removes oxygen from air, not nitrogen. Thus, an asphyxiation hazard exists inside enclosed spaces containing wet activated carbon. Dry activated carbon requires no special precautions. Rinsing activated carbon before first use is a sensible procedure as many carbons, particularly the 'stone' carbons, are produced using chemical etchants which may still linger in the final product (eg. zinc chloride and phosphoric acid). Those are the impurities you want to remove before letting newly procured carbon anywhere near liquids that you are later going to drink.

    I've found, however, that it does pay to filter even when the liquid seems crystal clear. Microscopic particles of carbon dust don't settle out, and they are chock full of congeners. Used to worry me that my carbon wasn't working properly until I tried filtering what seemed to be "pure" stuff. The flavor/smell improved immediately and the residue on the filter paper confirmed the presence of that suspended carbon. BTW, I don't bother with expensive filters ... just take a couple of feet of toilet paper and roll it up into a cigar. This gives me a tube of filtering paper that I can cut into whatever lengths I like (usually two) and then gently push into the neck of a large funnel. The harder I push, the finer the filter. Works a treat!

If you are trying to make a flavored spirit, eg whiskey, grappa, etc DO NOT polish it, because you will remove the flavor that you have worked so hard for.

Don't add any essences or flavoring until AFTER you have polished the spirit. If you add them beforehand, the carbon will adsorb a minor amount of the flavor compounds and aromatics from the essence.

Do not try to reuse your carbons as they are - they are loaded with all the crap that you don't want. You'll need to clean them (see below) before you reuse them.

Another trick is to add some activated carbon to the wash (eg with the sugar) for during the fermentation period. This will take out the cogeners as they form. Just make sure that you filter/decant off this carbon with the yeast, so that it doesnt go into the still (and release the nasties when heated). Its a good way of reusing older carbon that has been used & washed several times, and may be losing its effectivness.

To avoid having the "rough moonshine edge" or "off-taste / wet cardboard smell" in your spirit to start with, don't collect them. These impurities will be present more when using a pot still, less if using a reflux still, and just about absent if using a fractionating column. So one way is to use a taller packed column and increase the amount of reflux occuring. They can also indicate that you've tried to collect too much of the alcohol, and have run into the "tails"; so finish collecting a little bit earlier next time.


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