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Back in 2009, my colleague John Park published his Florence Siphon coffee brewing apparatus in MAKE Volume 17. That’s him above, goggling up before disengaging the safety interlocks on his infernal machine.

I have had the pleasure of meeting John on several occasions, but even if I only knew him through his hyped-up internet rock star persona, a few things would still be obvious. For one, he is irritatingly good-looking. Also, he takes his beverages pretty damn seriously. Here’s a small sampling of some classic JEP mixological fare:

So when I drew John’s name in this year’s MAKE Secret Santa gift exchange, I knew right away that I wanted to get him something beverage-related, something mad science-y, something finely-made, and like John’s coffee machine, something just a tad infernal. And then it hit me: A steam distillation setup.

Steam distillation is the process traditionally used to extract essential oils and herbal distillates from plants and other biological materials. These products find use in perfumery, medicine, food, and industry. It can also be used to produce fine flavored liqueurs, which I knew would be right up John’s alley. And it’s something I know a bit about. I published a simple design for an improvised kitchen steam extractor in MAKE Volume 22.

This improvised design works remarkably well for something cobbled together literally from odd pots and pans, but for gift-giving, especially hypothetical gift-giving, I wanted to do it up right, to design a steam extractor that would satisfy almost any hobbyist. For “fancy” work like this, the common cost-saving measure of using rubber stoppers and/or clear vinyl tubing is not a good choice, as the volatile components extracted during steam distillation can interact with these materials, degrade them, and pick up odd odors or tastes. And though fine stills can be made from copper, stainless steel, and other metals, I wanted this one to be all glass. I love the look of glass apparatus, and it’s especially cool to be able to watch what’s happening inside the still while it’s doing its thing.

In theory, the process of steam distillation is simple enough: Generate steam, direct it through the biomatter to be extracted, condense it, and collect it. In practice though, steam distillation is a subtle art, and the details of equipment and technique are very important. For instance, here is a common illustration of steam distillation that might appear, say, in a chemistry lab manual:

All the parts are there to satisfy the theory: The steam generator, the extraction vessel, the condenser, and the receiving flask. For practical use in manufacturing small batches of essential oil, for instance, this design has a couple serious problems…

  1. The extraction vessel is too small. The aromatic compounds in most plants are present in pretty low concentrations—a kilogram of plant matter is likely to yield only a few grams of essential oil, even under the best conditions. So you want the biggest extraction vessel you can practically use, so you don’t have to clean it out and recharge it many times to distill a useful volume of oil.
  2. Steam can condense in the extraction vessel. See how the design calls for steam to flow both in and out of the extraction vessel at the top? Some of that steam is going to condense inside the extraction flask, trickle down the walls, and pool at the bottom. And eventually the extraction flask will fill up with water, submerging the biomatter, and then you’re no longer doing steam distillation, but what some call “hydrodistillation,” i.e. just boiling your extracted material right in the still-pot. You can prevent condensation in the extraction flask by heating it, as well as the steam generator, but many perfumers, for instance, will tell you that directly heating the material you are extracting will alter or damage the oils that it yields.

A better design is shown here:

The bioflask, as you can see, is a lot bigger, but most importantly it’s been moved directly above the steam generator, and is ported at both top and bottom: Steam enters through the bottom neck, rises through the biomatter, and exits out the top neck. And most importantly, any that condenses inside the bioflask just drips back down into the steam generator. Sure, there’s a chance that small pieces of plant material may fall through the bottom neck, but that’s easily prevented, if necessary, by inserting a piece of wire screen or loosely-packed glass wool.

This apparatus, incidentally, is available as a set from Avogadro Lab Supply, who also sell a Florence Siphon kit based on John’s original article. Their price of $335 for steam generating flask, bioflask, still head, and condenser seems a bit steep, to me, however, so let’s talk a bit about paring that down. While we’re at it, we might be able to make some improvements, too.

The Steam Generator

Avogadro’s kit includes a 3000 mL round flask with a small flat surface on the bottom, which is useful for transferring heat from the flat surface of a hotplate, for instance, but otherwise doesn’t add very much. Plus, their flask has only one neck. 3000 mL is a big reservoir, but if you should need to add more water while the still is in use, you’ll have to dismantle it. A better option is a slightly smaller, traditional round-bottom flask with a second neck. Like the one shown to left, with a capacity of 2000 mL, currently available new on eBay for $52, including shipping. A 24/40 glass stopper for the second neck should add about $7 to the price.

To heat it, John can use the butane burner from his Florence siphon setup, or if I really wanted to spoil him, I’d watch eBay for a used electromantle, which is a hemispherical, fiberglass-insulated electric heater with a built-in rheostat. Electric power means John doesn’t have to worry about open flames, and the hemispherical shape means much more efficient heat transfer to a round-bottom flask. New, these are quite pricey, but they turn up in the used market all the time for about $100, and since the mantle doesn’t actually come in contact with the inside of the distilling glass, the problem of contamination on used equipment is much less of a concern.

The Bioflask

This is the most specialized piece of glass in the kit. Basically, it’s just a two-liter round-bottom flask with an extra neck in the bottom. The one sold by Avogadro Lab Supply has a wider joint on the top than on the bottom, which may be handy for loading and clean-out purposes, but isn’t going to affect the quality of the distillation itself much, if at all. A bioflask with 24/40 joints at both top and bottom should work just as well for distillation—it may just take a bit longer to put stuff in or take stuff out. And if you don’t care about the wider top joint, there’s no reason not to use a column chromatography reservoir for this purpose, instead of a specially-made “bioflask.” Here’s one in the same 2000 mL volume, new, from eBay seller labglass, for $65 including shipping. Bonus: flasks with same-sized top and bottom necks are more modular. If John needs to extract more than 2000 mL of material, he can just stack another chromatography reservoir (or more than one) on top of the first.

The Still Head

This is the top-most glass fitting that moves steam from the bioflask(s) over to the condenser. It’s known, logically enough, as a “transfer distilling adapter,” and has a downward-tilted arm to deliver any condensate to the receiving flask instead of back into the bioflask(s). The one shown here is from CR Scientific, and is a steal at $25, which we’ll call $35 to account for shipping. It has a top port that can be used to mount a thermometer or temperature probe for tracking the still-head temperature, or we can just close it up with another 24/40 glass plug (+$7).

The Condenser

The condenser that comes with the Avogadro steam extractor is known as a “Liebig” condenser, and is, I believe, their 300mm long unit. It features a long straight condensate pathway surrounded by a jacket with input and output barbs for circulating water or other coolant. Canadian eBay merchant Alchemylabs sells one in 400mm length for $49, including shipping to the US.

Finishing Touches

At this point, we’ve spent $216, including shipping, to assemble an apparatus that’s at least as good as the Avogadro bundle. We could even splurge for that $100 used electromantle and still come in at about the same price as their kit. A separatory funnel of, say, 250 mL capacity, like that shown to right, might be a nice touch, as well, since steam extractions tend to produce less-valuable water layers underneath (or above) the more-valuable oil layers. Directing the condenser to drip directly into a separatory funnel makes it easy to collect oil and water layers separately, into different containers, while the distillation is still running.

And that pretty much wraps it up. John, I hope you are pleased with your gift. It cannot be returned. And if you don’t want it, well, I think I know someone who does…

Sean Michael Ragan

I am descended from 5,000 generations of tool-using primates. Also, I went to college and stuff. I write for MAKE, serve as Technical Editor for MAKE magazine, and develop original DIY content for Make: Projects.


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