Carbon filter or dilute first, and why the order matters

Where the law sits, before anything else

This one matters and it gets stated backwards constantly, so here it is straight. Owning a still is legal and we can sell you one. Distilling spirits at home needs an excise manufacturer licence from the ATO, and not having one isn't a technicality. Flavouring a bought base spirit with an essence needs no licence at all, and that's the route most people in a shed are actually on.

Everything below assumes you're working within that. If you're not sure which side of it you're on, the ATO is the one to ask, not us and not a forum.

The two jobs, and why the order is a real question

A spirit that has just come off a still is high strength and it carries compounds you don't want in the glass. Two things fix that. Activated carbon takes out the off notes, and water brings it down to a strength you can drink.

People tend to treat these as a list and do them in whatever order the kit instructions happen to print. They interact, and the order changes the result.

Dilute first, then filter

Carbon works by adsorption, which is compounds sticking to the surface of the carbon rather than dissolving into it, and how well that works depends on the strength of the liquid running past.

At very high strength the alcohol itself competes for that surface, and the unwanted compounds stay dissolved in the spirit rather than moving onto the carbon. Bring the strength down first and those compounds are much more willing to leave. The practical effect is that the same amount of carbon does more work on a diluted spirit than on a raw one.

So the order that actually works is: bring it down to roughly the strength your kit's instructions nominate for filtering, filter it, then bring it the rest of the way down to drinking strength afterwards if you need to.

Use water that doesn't bring its own problem

The other half of this is what you dilute with, and it's the commonest cause of a bottle that goes cloudy hours after you were pleased with it.

Tap water here carries dissolved minerals and often chlorine. Chlorine gives you a flat chemical note that gets worse with time, and hard water can drop a haze out once the strength falls. Distilled or demineralised water costs very little and removes the whole question. We keep it in 4 litre and 10 litre containers in the shop.

Add the water to the spirit rather than the other way around, and go slowly. Let it sit for a few minutes between additions, because the mixture warms as it combines and a hot reading will tell you the wrong strength.

Then rest it

A freshly diluted spirit tastes harsher than the same spirit will taste in a fortnight, and a lot of people filter twice chasing a fault that would have settled on its own. Give it a couple of weeks in a sealed bottle before you judge it, and only then decide whether it needs more work.

Flavouring comes after all of this, never before. An essence added to a spirit you're about to run through carbon is an essence you're about to strip back out again.

Shop related products

• Still Spirits Turbo Carbon. Liquid carbon for cleaning up a wash before it ever reaches the still.
• Still Spirits Air Still Carbon Pack of 10. Carbon sachets sized for an Air Still run.
• Still Spirits Oak Cask 50ml. Oak flavour, added after filtering rather than before.
• Still Spirits Bourbon Essence 50ml. A flavouring for a bought or finished base spirit.

Did you know we also stock distilled water in 4 litre and 10 litre containers, universal carbon and filter papers, the Air Still and its fermentation kit, hydrometers and fermenters, none of which are on the website. Give us a ring on (08) 8536 4333 to check what's on the shelf.

More in the homebrew range, and Brewhilder will answer a question if you'd rather ask than read.

Read next

• Still Spirits kits may be legal, but is your hobby putting you at risk. The licence question on its own, and the one to read first.
• How to distil your first batch at home. The run itself, which is the step before this one.
• Why your base spirit decides how the essence tastes. What happens after the filtering is done.

I still measure strength while it's warm, get a number I don't believe, then do the whole thing again cold like I should have.

Cheers,
Candeece

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