How full to fill a still boiler, and what to do when it foams
A foaming boiler is a safety problem before it's a flavour problem
Most of what gets written about foam in a still treats it as an annoyance that spoils a run, and that's only the small half of it. A boiler that foams hard pushes liquid wash up into the vapour path, and that's worth taking seriously, because a partly blocked vapour path on a sealed vessel full of hot alcohol is the one thing in the whole hobby that can genuinely hurt you. Everything below is written in that order, safety first and flavour second, because that's the order it actually matters in.
Where the law actually sits
Worth saying plainly, because it gets muddled constantly. Owning a still is legal in Australia and we're allowed to sell you one. Distilling spirits at home is the part that needs an excise manufacturer licence from the ATO. That's a real licence with real conditions attached, not a formality anybody gets to skip. Flavouring a base spirit you have bought is a different activity altogether and needs no licence at all, so that's the road most people end up taking.
Headspace is the fix, and it's the one people skip
The single biggest cause of wash ending up where it shouldn't be is a boiler filled too full, and it's a tempting mistake to make because nobody wants to run a still twice. Leave real headspace above the wash and follow whatever your own boiler manual says rather than a number off the internet. Treat that line as a hard limit instead of a suggestion. A run that's 20% smaller than you wanted is a far better outcome than a run you have to stand over with a spanner.
What to do when a run starts surging
If you hear the thumping or you see the sight glass load up, then the order you do things in matters, so here it is. Turn the element off first and leave it off. Then stay away from the boiler while it's hot, which means no leaning over it and nothing opened up until the whole thing has cooled, because that vapour is hot alcohol and it will scald you long before you have worked out what you were looking at. Let the whole thing cool right down on its own, and only then go and find out what happened.
Leaning in with a torch to see what's going on gets written about often enough that somebody ought to say otherwise, so I will. A run that's misbehaving is the one moment when your face should be as far away from the gear as you can get it.
Why it foams in the first place
Sugar washes and anything carrying a lot of protein or suspended solids will hold gas and throw foam when the heat comes on, so a cloudy wash is a foamy wash more often than not. Letting the wash settle properly before you transfer it, or clearing it with a refiner such as Turbo Clear, takes most of the cause away before you have even switched on. A crusted heating element is worth a look too, because a dirty element makes hot spots and hot spots make the boil uneven.
Where a conditioner comes in, and where it does not
Still Spirits Distilling Conditioner is a preventative. It goes in before you switch on and breaks down the surface tension so that foam never builds in the first place. On a well filled boiler with a clean wash it does that job well. What it isn't is a rescue for a run that's already surging, and it isn't a substitute for headspace either. Add it at the start and keep the fill level honest, because the two of them together do far more than either one on its own.
Shop related products
- Still Spirits Distilling Conditioner 50ml. Goes in before you switch on, to stop foam building.
- Still Spirits purt Turbo Yeast. A cleaner ferment leaves less behind for foam to work with.
- Still Spirits Universal Z Carbon. For polishing a base spirit once the run is safely finished.
- Still Spirits Top Shelf Whiskey Essence 50ml. A whiskey profile for a clean base spirit.
Did you know we also keep Turbo Clear, Turbo Classic Yeast, a standard glass thermometer and the two scale hydrometer with test jar in the shop. Plenty of the spirits gear isn't on the website at all, so ring us on (08) 8536 4333 and we'll check the shelf for you.
The rest of the range is in our homebrew collection.
Our homebrew adviser Brewhilder will talk you through your own setup if you would rather work it out that way.
Read next
- Still Spirits whisky profiles, what they do and the law
- Still Spirits English Dry Gin essence, how to use it
- Still Spirits Cedar Oak Profile, what it does
I'm cautious about heat and pressure to the point that people find it funny, and I have no plans to get more relaxed about it.
Cheers,
Candeece
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