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How can I replicate this cold coffee dripper thingy with off-the-shelf components?
July 6, 2011 10:46 PM   Subscribe

This doesn't look like $265 of laboratory glassware, but that could be because I don't know the first thing about buying laboratory glassware beyond buying some $5 borosilicate flasks once for making yeast starters, and ignorance breeds confidence. How would one go about effectively replicating this device with off-the-shelf components from an online lab supplier? Extra lives for links!
posted by obiwanwasabi to Technology (24 answers total) 14 users marked this as a favorite
(I should add that I know about plastic Toddy systems and the like - I'm looking for something glassy and sciencey. And cheapy.)
posted by obiwanwasabi at 10:47 PM on July 6, 2011

You may want to look at organic chemistry glassware, such as a flat-bottom flask or beaker, B├╝chner funnel and separatory funnel, along with clamps and racks to hold the separate pieces.

I'm sure the Internet has lots of places to shop for this kind of gear; I have no specific recommendation here. Perhaps you could talk to a local high school or college to see if you can get in on a purchase of little bits and pieces, in exchange for a class demonstration.
posted by Blazecock Pileon at 10:56 PM on July 6, 2011

Lab-grade glassware doesn't come cheap. Unusual items and large sizes in particular can be pretty pricey - I wouldn't be surprised if a large enough Buchner cost something in the order of $100.

As to on-line suppliers, check out Sigma Aldrich for a large catalog that probably contains everything you need in one place but not necessarily cheap, and American Science & Surplus for good deals and odd finds.
posted by Dr Dracator at 11:25 PM on July 6, 2011

I would buy this old vacuum pot.

You won't be competing with collectors on this one, because the funnel and glass filter rod were made by Cory, and the lower vessel comes from an entirely different line of pots sold by Wards.

It's not clear to me they would even function together as a vacuum pot because they might not form a tight seal with each other, and even if they do, the stem of the Cory funnel doesn't come down close enough to the bottom of the lower vessel to brew an optimal pot of hot coffee.

You could make cold coffee with this by putting grounds in the funnel with the filter rod in place, adding water, and waiting for the coffee to drip down into the lower vessel. I use a vacuum pot with a Cory rod to make my coffee every morning, and I can testify that the glass filter rod is about two orders of magnitude more efficient than a French press at removing coffee grounds. It won't be quite as efficient with adding water through the mouth of the funnel, because water welling up from below sorts the grounds so that the largest are at the bottom and the smallest on top, which makes the coffee more effective at filtering itself.

You could control the rate at which the coffee drips down by putting an almost airtight seal on the mouth of the funnel, inelegantly with something like Saran Wrap.
posted by jamjam at 12:54 AM on July 7, 2011

It most certainly looks like $265 of glassware to me. Lab glassware is expensive, mostly because the old good glassblowers are dying out and people are unable to make their own things anymore.

To make that you would need/want:

1) Addition funnel or Separatory Funnel for the dropping water bit. A 500 mL one costs 29 UKP from a cheap place. The same thing with a teflon stopcock, which you will want because you dont want to grease the joint is 32 pounds.

2) Either a frit or a buchner probably 300 mL size is 42 pounds.

3) A flask or a beaker to collect the filtrate That is cheap and can be had for a tenner.

SO you are looking at 80 pounds 100 pounds with shipping. Now to ship it to australia would be much more. This is a very cheap place somewhere in Aus that I found has just the dropping funnel above for 273 AUD. If you shop around you might be able to find it cheaper, but I think it is in the correct ballpark.
posted by koolkat at 1:36 AM on July 7, 2011

Thanks - just the terms 'Buchner', 'separating funnel' etc have led to much more fruitful Googling than 'round drippy glass thingy'. And yes, the less something looks like a flask, the much, much more expensive it seems to be. $265 looks like a right bargain now.

The best I've been able to do so far:

500 ml borosilicate Erlenmeyer flask - $3.70 (the bottom bit that holds the finished coffee)

500 ml separatory funnel - $27.50 (the top bit that drips water over the coffee grounds)

The middle bit is tricky: I can't seem to find transparent glass Buchner funnels, only porcelain or plastic; and I'm not sure what size I'd need, because the quoted diameter doesn't really tell me how much coffee and liquid it would hold. Any suggestions? It really just looks like a French press with a hole in the bottom and the top part of the plunger knocked off. (Putting a hole in a glass French press flask without shattering it sounds like a challenge, though.)

a teflon stopcock, which you will want because you dont want to grease the joint

I have no idea what that means, but it doesn't sound good. Are you saying that a glass stopcock (like the one on the funnel I linked above) will leak?
posted by obiwanwasabi at 2:43 AM on July 7, 2011

It won't leak, but you'll need to grease it with vacuum grease which likely isn't something you want in your coffee.

An individual teflon (PFTE) stopcock shouldn't be too hard to source.

Buchner funnels tend to be porcelain. They're actually nice looking like that.

Also: yes, that looks like an expensive collection of lab glassware.
posted by sciencegeek at 3:10 AM on July 7, 2011

Addition funnels will work better than a sep funnel for adding water slowly, if you need it to be very slow.
posted by Dr.Enormous at 3:53 AM on July 7, 2011

I was looking at that Hario rig the other day. It's pretty, but I'm frankly a bit skeptical about its effectiveness. I mean, the cold water just doesn't spend that much time in the grounds--minutes, instead of the 12+ hours most cold-brewing methods ask for. (Does anyone know if it actually works?)

I was also turned off by the plastic toddy system, for aesthetic and functional reasons (it's a single-task device, kinda ugly, has proprietary filters, it seems like it could tip over, and there's no cover (?) for the main container).

But I love cold-brewed coffee. Here's my system. It's not glassy or sciencey, but it's cheap, easy, and works in large quantities.

First, I combine the coffee grounds and water in a Frigoverre pitcher like this (I love these things; the wide-mouth ones, as linked, are easier to clean than the narrow ones). I let that sit at room temperature for 12-18 hours.

I then put a gigantic coffee filter in the steamer insert for my stock pot. It can hold a lot of liquid at a time and the large surface area means it doesn't clog (I'd go through 3-4 regular filters per liter of coffee concentrate before, which was a messy hassle). I put the steamer insert into the stockpot, dump the jug of water and grounds into it, and walk away. After half an hour, I come back, rinse out the pitcher, transfer the coffee concentrate from the stockpot to the pitcher and put it in the fridge. Delicious iced coffee for an entire week!

Really easy, and if you already have a big jar, a stockpot, and a steamer (or even a colander), the only additional expense is the coffee filters.

Doesn't look as cool as the Hario system, though, that's for sure. But I reckon it makes better coffee.
posted by kprincehouse at 4:24 AM on July 7, 2011 [6 favorites]

krpincehouse, since you sound like an expert, may I ask what ratio of water to grounds you use? And what fineness of grind you use? And whether you dilute before drinking and how much?
posted by Aizkolari at 6:21 AM on July 7, 2011

I detest ground glass joints because they always get stuck unless you grease them well. Of course this is in a lab where I am trying to purify things so some of the grease invariably gets into said thing I am trying to purify. I now only use PTFE or teflon stopcocks as they will rarely sieze.

With this setup I think you would be promed for disaster because I think that they key things is to get the addition rate equal to the elimination rate to avoid spills from overflow. Fiddling with ground glass joins isn't a good idea because they will sieze. In the original setup they used a steel stopcock, but you'll never find one of those without making it yourself. I am sure you could just use a bit of olive oil or bacon fat to grease the joint, but then again would you want that in your coffee because a very small amount is going to come through.

As far as a clear buchner you need to look for a sintered glass funnel, we've got tons in lab, but then again I wouldn't EVER use them for making coffee as I am sure it will at least impart off flavours if not toxic chemicals.
posted by koolkat at 6:26 AM on July 7, 2011

Looking for "glass frit filter" yielded some funnels of the type you're looking for, like this. Still likely to be pricey though; I found a similar filtration setup to what you're looking for on VWR for 290 and that seems about right.

(I once did an undergrad research project that involved having a bit of money for lab supplies. We had about 1000$ left over at the end and went on a shopping spree for glassware the whole lab would find useful. I can't remember exactly what we bought but I remember that it all fit in my backpack easily.)
posted by tchemgrrl at 6:49 AM on July 7, 2011 [1 favorite]

As others have said, scientifc glass is quite expensive. The things that make glassware expensive are frits, porous filters, and ground joints. If you're looking to economize, you want to minimize both. Haro has actually cheaped-out here; they're using silicone connectors instead of ground joints as far as I can tell.

Here's one way you could do this:

Top: Separatory funnel with a teflon stopcock + ring stand. It looks like you'll want a 1-L size flask. Here's one on eBay with a support stand (which you'll also need) for $90. That's a good price, I think. I'd pay twice that from a scientific supply house (but I'd get it within 24-hrs---when we break something we often want a replacement immediately).

Middle & bottom: A Buchner funnel on an Earlenmeyer flask. Here's a rig on eBay for $75. You don't really need the pump, but whatever. The 100-mL funnel may be a bit small. You might want something in the 250-mL to 400-mL range. That's a porcelain funnel which has the advantage of being cheap and easy to clean. You will need to use a paper filter (which you can cut from a regular basket filter) with the procelain funnel. Another option would be to use a glass one like this one for $80, but then you need to buy the rubber gasket and the flask extra. The glass funnels don't need a filter, but they can clog fairly easily and the frit will stain brown-black after a few uses.

So total, $165 to $200 with almost no searching for best price or other deals. Look around eBay and you'll find some better prices, I'm sure.

Everything should be dishwasher safe, btw.

I'd want to be very sure that any glassware, particularly used, was well washed prior to use. Her's how I'd do it: wash well with soapy water, rinse 3 times with no soap then allow to drip dry. Finally, bake it in your oven at 350-400 F for an hour to be safe.
posted by bonehead at 9:40 AM on July 7, 2011

but then again I wouldn't EVER use them for making coffee as I am sure it will at least impart off flavours if not toxic chemicals.

Oh yeah this bears repeating: you don't ever EVER use glassware that has seen the inside of a lab for eating/drinking. In fact, you don't use brand new lab glassware that just came out of the box either: You don't want to get used to drinking out of a lab beaker (might pick up the wrong one in a moment of confusion), and you don't want beakers of stuff that might be either poisonous or drinkable going around the lab. This kind of concern probably doesn't apply to the OP, just putting it out there for people who might come across the thread.

That being said, I might as well contradict myself: A lot of the cost of lab supplies is due to logistics concerns - there are so many different specialized items, sourcing and keeping each one in stock is a major task (another part of the cost is simple economics, with suppliers gouging labs for all they can get, but I digress). If you manage to get in touch with a local supplier with an actual physical presence in your area, you might find you can get low-cost versions of common items they regulary keep in stock at prices much lower than what you get on the internet.
posted by Dr Dracator at 9:45 AM on July 7, 2011

You don't want to get used to drinking out of a lab beaker (might pick up the wrong one in a moment of confusion), and you don't want beakers of stuff that might be either poisonous or drinkable going around the lab.

! and further !?! Drinking/eating in a lab is one of those "serious talk" offenses that can very quickly lead to "get your coat" ones.

You point about not using used glass it well taken though. He's not going to be able to do an alcoholic KOH or perchromic acid clean of this glass.

OP, stick to buying new.
posted by bonehead at 9:55 AM on July 7, 2011

! and further !?! Drinking/eating in a lab is one of those "serious talk" offenses that can very quickly lead to "get your coat" ones.

I was referring to the cuteness of getting a beaker and keeping it at your desk for use as a coffee mug. Food/drink/smoking/other hand-to-mouth activity is an obvious no-no in the actual laboratory.
posted by Dr Dracator at 10:01 AM on July 7, 2011

Thanks again!

To be clear, I make cold brewed coffee now using a glass jug in the fridge followed by a couple of runs through a French press to filter. I'm happy with the flavour and convenience. This little experiment is purely so I can have something pretty to stick on my desk, have a morning ritual of adding some water in the top, and then be able to watch stuff bloop through it during the day.

It might not make sense to try to recreate the middle bit from lab glass when so many glass / stainless sciencey-looking alternatives already exist in the coffee world. For example, I could stick a stainless Coava Kone in a simple glass funnel instead, then have that drip into a flask. It'd be $60, but I could also take the cone with me into the field.

I'm not too worried about a ground glass stopcock sticking, because I'd really only have to set it once and then leave it open - so long as the middle and bottom bits were in place, it wouldn't really matter if the top started dripping straight away.

I'll keep thinking about it. In the meantime, cheers for your cold brewing tips, and thanks for the crash course in lab glassware!
posted by obiwanwasabi at 7:36 PM on July 7, 2011

(Ha! Looks like the Coava folks have the same idea.)
posted by obiwanwasabi at 7:49 PM on July 7, 2011

By sticking I don't mean becomes hard to turn and then releases I mean it seizes and to get it unstuck requires a torch. A proper torch with a flame and not a flashlight. You would still want to be able to adjust the flowrate of your dropping funnel because obviously you are going to want it closed for filling and also be able to adjust the rate so that it matches the rate of elution from the grounds.
posted by koolkat at 2:10 AM on July 8, 2011

Yeah, I thought you meant 'stuck, forever', but I figured I'd just fill it once it was in place, so it wouldn't matter if it started flowing straight away, and that as I use the same grounds, I'd only have to set it once. But I suppose it could seize the first time out of the box, or I could decide to change my grind, and while I do have a torch, that sounds like a fair bit of mucking around. I'll have to keep looking for a non-glass stopcock that doesn't look like it belongs on a swimming pool pump with garish blue and white plastic.
posted by obiwanwasabi at 3:01 AM on July 8, 2011

The one on the Coava link you gave earlier is exactly what I meant. That is nearly identical to the ones we have here in lab, except that we have multiple different sizes and they are colour coded.
posted by koolkat at 3:18 AM on July 8, 2011

Cool - will look for one of those. Can you get them separately to slide over the stem of a filter funnel, or are they always built in?
posted by obiwanwasabi at 5:36 AM on July 8, 2011

They're never built in, but would be a very easy thing for a glassblower to make assuming you could find one.
posted by koolkat at 5:56 AM on July 8, 2011

That Coava device won't produce the cold-conentrate as easily or as well though---you need better control of the residence time of the liquid in the coffee to do that. What you're looking for is a what chemists call a packed column. This is a device that controls the time and rate of exposure of the water to the coffee, and allows you to fine tune the extraction. That's also why controlling the drip rate is so important.

It struck me last night that a perfect device for this is the Aeropress. More specifically, if you use just the filter part, without the plunger, you could very easily make a reproducible, controllable packed column with it. Assemble with filter at the bottom, loosely pack with coffee, set over a container, then all you need is something with a controlable drip rate to add water on top. The Coava funnel could do that for you.

The problem with using a conical funnel is that your solvent front doesn't move at a constant rate through the material. Coffee in the pointy end at the bottom will probably get more extracted than coffee at the top and you may not get an even flavour profile. It's important if you want even, efficient extraction to use a column with straight sides.

Powder funnels (like the Coava one) are great for filtration and removing components (you just add way excess of your exchange medium), but they're not the best choice for extraction or separation, which is the problem of brewing coffee.

So, you need something to control the drip rate at the top, a packed column with your coffee in the middle and a collection resevoir in the bottom. You can combine the first two and get a decent cup of coffee (as a Chemex flas does, for example), but for something that needs a long residence time like the toddy method, I think you'll get better results if you have an even controllable exposure, rather than the extraction gradient that the conical funnels will give you.
posted by bonehead at 8:55 AM on July 8, 2011

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