How strong of a coffee can I make?

January 23, 2008 7:50 AM

CoffeeFilter: Will recycling coffee through my coffee maker create a Super Coffee?

If I were to make a pot of regular old Folgers coffee, and then dump out the grounds and put fresh coffee in the filter, and then pour the coffee I just made into the reservoir and make another pot, and then keep doing that...how strong will the coffee get?

Is there a maximum caffeine saturation? I recall that an average cup of coffee has about 100mg of caffeine. Can I make deadly super-crack coffee? Or will the coffee turn too thick and not filter properly after a few dozen cycles?

posted by ian1977 to food & drink (43 comments total)

No. You'll ruin your coffee maker and make horribly acidic, burned tasting coffee.

You're essentially boiling already brewed coffee. This is never a good idea as it spoils the volatile oils that make coffee taste good.

Mind you, you might increase the caffeine, but it'll be almost undrinkable.
posted by generichuman at 7:57 AM on January 23, 2008

I'm in the process of doing this right now. My version is a little lower tech - I use a pot, a funnel thingey, a filter, grounds and hot water. I don't use any measurements, so I can't give you a quantitative answer. It gets deadly after its third pass through, though.
posted by Ctrl_Alt_ep at 7:57 AM on January 23, 2008

I would guess most/all of the caffeine would leach out during the first cycle (at least that's how it works for tea)...
posted by Gee Your Hair Smells Terrific at 7:58 AM on January 23, 2008

Coffee is also extremey acidic, and not necessarily good for the internal workins of your coffee maker which are used to nice, clean water.
posted by generichuman at 7:59 AM on January 23, 2008

What you're looking for is a French press. You can let that sit and brew for as long as you like before you push the plunger.
posted by Burhanistan at 8:00 AM on January 23, 2008

Yes, the strength would increase by percolating coffee through coffee. You could also just brew regular coffee and boil it down to mud. You could also grind the beans finer, compress the grounds into a sort of puck and force the hot water through it under pressure, to create this mysterious super-coffee to which you refer, which is also known as espresso - the only way you're going to get something palatable (there is no method of pleasurably concentrating commonplace drugs that hasn't already been done, my friend).

Yes, there are always limits to how much of a particular solute you can dissolve in a given solvent. Past that stuff starts to precipitate out spontaneously. Your coffee would probably hit the saturation point with solutes other than caffeine, which is a minority constituent of coffee. If you wanted super-caffeinated coffee you could, like dissolve a no-doze in it or something. Frankly, if espresso isn't doing the trick for you, you need to seek help, not stronger coffee.
posted by nanojath at 8:00 AM on January 23, 2008 [3 favorites has favorites]

I realize that this isn't truly answering the question because I can't tell you how much caffeine will be in your coffee, but I will tell you that if you do this you will have a pot of disgusting rancid bilgewater. I Other people have already tried this so you don't have to.
posted by pieoverdone at 8:00 AM on January 23, 2008 [1 favorite has favorites]

Sorry, misread your question, you're not reusing the same grounds...how about making a large amount of coffee then slowly reducing it over low heat on a stovetop?
posted by Gee Your Hair Smells Terrific at 8:01 AM on January 23, 2008

Holy crap, have you considered an espresso machine? That seems like it would be a lot of effort for some really bad tasting coffee. They sell some pretty cheap ones at Walmart :P
posted by Sufi at 8:01 AM on January 23, 2008

generichuman has it. If you really want to make super caffeinated coffee, just use more grounds.
posted by gauchodaspampas at 8:07 AM on January 23, 2008

I've done this, there's better ways to make strong coffee. I would recommend the French Press; they are cheap and last forever if taken care of, and don't require the constant purchase of filters.
posted by jtron at 8:07 AM on January 23, 2008

Mind you...I have zero intention of doing this...I just wanted to satisfy my curiosity. ergo, the desirability of drinking this concoction plays no part in my question. :-P

Espresso won't do the trick, unless you re-run the espresso through the machine. Although, it would probably take less cycles to create said Super Coffee with an espresso maker rather than a regular coffee maker.

jtron: When you did this...how many cycles did you do? Did it get thick? Did you drink it?
posted by ian1977 at 8:11 AM on January 23, 2008

You can also easily make espresso-strength coffee at home with an "Aeropress", a syringe-like gadget somewhat similar to a French press. I wrote a review of the Aeropress a while ago, here; it is neither expensive nor difficult to use.
posted by dansdata at 8:14 AM on January 23, 2008

You can just cold-brew coffee in the refrigerator overnight. Grind some beans, put them in any container with some water, and let it sit as long as you want. There's your Super Coffee.cold
posted by kcm at 8:15 AM on January 23, 2008

Here is a roundabout answer to the real question as I perceive it, which is how to get super-crack coffee.

The answer is cold-coffee brewing. You need a toddy, one of the special filters, a carafe, and a plug. Basically, this. You put in a pound of coffee ground relatively coarsely, pour about 4 cups of cold water in carefully, let it sit for a minute to let the grounds settle down, then pour in 5 more cups of water. Then you let the whole thing sit for about 18 hours. Hold the toddy over the carafe, remove the plug, set it down, and let it drain.

What you'll end up with is super-concentrated cold-brewed coffee. Because it hasn't been exposed to heat, it is both less acidic than regular coffee and contains much more caffeine. We used to make our house iced coffee this way when I worked as a barista, and I subsequently bought a toddy set for home. You dilute the resulting concentrate by 2 to 1 -- two parts water to one part concentrate. Delicious, smooth iced coffee.

When you want serious stuff (i.e., your hoped-for supercoffee), you can drink it undiluted, but I recommend a fair amount of cream and sweetener -- because it is supercoffee, and it will be pretty bitter. We were technically strictly forbidden to do this at the coffeeshop where I worked, but when you're trying to get through closing & cleanup at 1AM after a full shift, you can be sure we drank the coffeecrack. And it was awesome.
posted by tigerbelly at 8:17 AM on January 23, 2008 [27 favorites has favorites]

Ah, now I see that you have no real practical interest in this question. Never mind! I hope it helps someone else who is looking for the delicious hum of hypercaffeination and smooth, tasty coffee-crack.

FYI, for those people: espresso has less caffeine than a cup of regular drip coffee. Likewise, dark roasts have less caffeine than lighter roasts -- the more heat the bean is exposed to, the less caffeine there is in the resulting bean. I always had a hell of a time getting kids studying for exams to understand that the fact that their coffee tasted stronger did not mean it was stronger.
posted by tigerbelly at 8:23 AM on January 23, 2008 [1 favorite has favorites]

1,3,7-trimethyl-1H-purine-2,6(3H,7H)-dione (caffeine) has a solubility in water of 180mg/mL at 80C. This is probably hotter than you want to drink your coffee, but it does suggest an upper bound to exactly how much caffeine you could theoretically get in the water. I don't think you'll get that from straight hot water extraction; If you want the highest possible caffeine concentration, you'll want to brew a large amount of coffee, then boil off the water. This will, of course, be both extremely unpleasant to taste and toxic. LD50 in rats is 192 mg/kg; doses in excess of 400mg in humans will cause adverse effects.
If all you're interested in doing is extracting the caffeine, you're better off using a different solvent, or just buying No Doz.
posted by leapfrog at 8:24 AM on January 23, 2008 [1 favorite has favorites]

You can do this very easily using an Aeropress that's been mentioned above and you won't get the burned flavor that you'd get by cycling through a machine. I've cycled my coffee through the Aeropress multiple times to make the coffee stronger. It's a fun gadget to use if you are really particular about the strength and flavor of your coffee because you can experiment by how much coffee you use, how much water you put in to mix it, how long you mix it, how fast you press it etc.
posted by any major dude at 8:26 AM on January 23, 2008

CoffeeFilter.... heh.
posted by Doohickie at 8:26 AM on January 23, 2008 [2 favorites has favorites]

French Press or my preferred method Cold Brew will get you a condensed base that you can add multiples of to any drink for the penultimate overdose.
posted by prostyle at 8:43 AM on January 23, 2008

I did this any number of times when I worked by myself in an office every weekend, especially the 12 hr days. It was truly awful coffee, and it started me down the road to a lot of heartburn. However, I didn't just get a jolt, I didn't just shake - I *vibrated*, and the whole world vibrated with me.
posted by notsnot at 8:43 AM on January 23, 2008 [3 favorites has favorites]

I'm not sure where people are getting the impression that espresso has loads of caffeine. If anything, the speed of brewing reduces the amount of caffeine you get.

You get much more by using a french press, where the coffee steeps for about 4 minutes.
posted by O9scar at 8:44 AM on January 23, 2008

No one seems to have mentioned that if you use a regular drip coffee maker the water is boiled before it goes through the coffee, so anything you add to it will be removed as the water turns to steam. So the second pass of coffee through a traditional drip machine will simply leave crap all over the boiler element and make pretty normal coffee.

You could boil coffee and pour it directly through the grounds and then you'd have a percolator, which most people say makes pretty horrible coffee.
posted by GuyZero at 8:49 AM on January 23, 2008

Caffeine goes into solution from ground coffee (or tea, for that matter) very quickly, so the relatively rapid brewing time for normal espresso does not mean it has less caffeine in it.

A little cup of espresso actually has much the same amount of caffeine in it as a normal-sized cup of ordinary coffee. This is hardly surprising when you take into account the fact that coffee shops often make a cup of ordinary coffee by adding water to an espresso shot.

The Coffee FAQ site has a good page about the "espresso has less caffeine" myth.
posted by dansdata at 8:51 AM on January 23, 2008

The caffeine content of espresso is higher than brewed coffee in a per-volume basis.

The confusion comes in that a serving of espresso contains less caffeine than a serving of coffee. However, the shot of espresso is significantly smaller than your cup of coffee. Anyone who's worked at a coffee shop can tell you that pulling a sextuple shot to fill a coffee cup is a huge kick in the pants compared to a cup of normal coffee.
posted by explosion at 8:55 AM on January 23, 2008

tigerbelly, according to this FAQ, the cold brewed method (which I still recommend) reduces the caffeine by about 1/3 by volume. FYI. However, because its a concentrate, you could always add more, of course, to create your desired mud.
posted by elendil71 at 9:00 AM on January 23, 2008

I'm not sure where people are getting the impression that espresso has loads of caffeine.

Because it does - 3-4X by volume. Espresso brews a larger amount of coffee per volume of water under pressure, which factors contribute to a higher concentration of caffeine as well as other constituents.
posted by nanojath at 9:01 AM on January 23, 2008 [1 favorite has favorites]

I might have missed it, but a good way to get super-duper nutso crackoffee is to brew it with Water Joe. All the yummy of properly-made coffee, enough caffeine to give an ER surgeon a heart attack.
posted by TheNewWazoo at 9:12 AM on January 23, 2008

Because it does - 3-4X by volume.

The type of coffee bean used in espresso often has half the caffeine of regular beans. I have to think those numbers are not quite right, or are not consistent between coffee bars.
posted by Blazecock Pileon at 9:13 AM on January 23, 2008

As most of the above mention, the only real flaw in your plan is the BOILING. If you use any brewing method that does not boil the water (or in your plan the coffee) first, you will not ruin anything.

Experiment away!
posted by rokusan at 10:01 AM on January 23, 2008

Interesting NYT article on coffee today, if you have $20,000...
posted by pithy comment at 10:17 AM on January 23, 2008

Even more than a French press, I recommend investigating the world of Turkish coffee and the ibrik.
posted by Wolfdog at 10:42 AM on January 23, 2008

(See also)
posted by Wolfdog at 10:44 AM on January 23, 2008 [1 favorite has favorites]

For a great caffeine kick try a double espresso topped with a filter coffee. Just like americano but you are using coffee from a French Press instead of water to top your cup up. Tastes great as well!

As a side note I've been experimenting with putting dried chilli in with my coffee for blow your head off espressos. Deeply satisfying and an experience well worth trying imo.
posted by twistedonion at 10:48 AM on January 23, 2008 [2 favorites has favorites]

tigerbelly, according to this FAQ, the cold brewed method (which I still recommend) reduces the caffeine by about 1/3 by volume. FYI. However, because its a concentrate, you could always add more, of course, to create your desired mud.

Well, hell! That noted, brewing it for 18-20 hours as I was taught to do (6+ hours longer than the typically recommended 12 on the various Toddy websites) will deliver more caffeine in the resulting liquid than the average they refer to.

Yep, just double-checked, this is noted on the Toddy Cafe website:

"You may cold-brew your grounds longer than the recommended 12 hours. However, if you do, more acidity and caffeine will be absorbed into the liquid (although the amount of acidity and caffeine will never be as much as coffee brewed by conventional hot water methods). The trade-off: Richer concentrate will be produced (with the same amount of liquid), therefore allowing you to produce more cups of coffee per pound of coffee beans."

Also, the toddy-makers apparently typically recommend a 3-to-1 ratio, rather than a 2-to-1 as I use. Ultimately my ingrained method demonstrates I necessarily must agree with your last remark -- you can also definitely compensate (as I apparently do) by diluting the concentrate less as well.
posted by tigerbelly at 11:06 AM on January 23, 2008

In addition to the many fine pieces of advice mentioned here for maximum caffeination, consider cowboy coffee. Basically just boil water (over a campfire, preferably), add grounds, return to boil, and let simmer all day. The joke is that it's supposed to be thick enough that you can stand a spoon up in it.
posted by adamrice at 11:10 AM on January 23, 2008

tigerbelly, cold-brewed toddy concentrate not only is not "bitter"; it does not even taste like coffee. It's fine for a coffee-ish flavoured milkshake, but it's a terrible alternative for anybody used to the real thing (like espresso in my case).

I'm sure it's fine as a caffeine delivery system and it is less acidic (and again less flavourful) than coffee, but if OP just want caffeine: HEY OP, TAKE CAFFEINE PILLS!
posted by ethnomethodologist at 12:43 PM on January 23, 2008

You can buy caffeinated water and use that to brew coffee.
posted by dagnyscott at 12:49 PM on January 23, 2008

If you wanted super-caffeinated coffee you could, like dissolve a no-doze in it or something

I second this. If you are treating the coffee suspension as a delivery mechanism for caffeine, its efficiency and taste will decline as you push it past its "natural" bounds. Just drop a few hundred mgs of pure caffeine into your drink and you are good to go. You will get a more bitter taste, but not as bitter as if continually recycled your bean effluent. You can also buy pure taurine and add that for an extra buzz.
posted by meehawl at 1:00 PM on January 23, 2008

ethnomethodologist, I must disagree that it does not taste like coffee. It does not taste like espresso or French Roast, but it does taste like coffee. There are those of us who prefer a lighter roast made from less acidic beans, which produces a smoother cup -- and that is coffee as well. Indeed, a dark roast is often used to disguise inferior beans. However, I would never categorically conclude that all dark roasted coffee is shit coffee or not "real."

Personally I tend to prefer cold-brewed coffee in its more natural form as iced coffee, rather than heating it up -- you'll note I didn't recommend that the poster heat the resulting coffee, though I'm sure s/he could do so, nor did I suggest turning it into a fancy Starbucks frappuccino. I don't know why you are so het up about it. I'm not interested in having the classic (and quite tiresome) coffee enthusiast arguments about which is the One True Way, just answering the poster's question with a reasonable and feasible solution.
posted by tigerbelly at 1:52 PM on January 23, 2008

The type of coffee bean used in espresso often has half the caffeine of regular beans.

That's not actually true. Espresso is generally made from blends of varietals, and the blend is up to the blender (i.e. Blue Bottle Coffee sells four different types of Espresso, all of different blends). The range of caffeine amounts in Arabica varietals is from .58% to 1.89%, and any espresso blend is going to reflect that. An "Espresso" blend just means that that amount and type of varietal is (hopefully) going to stand up to the espresso brewing process, versus plunger pot or automatic drip or whatever.
posted by oneirodynia at 9:23 PM on January 23, 2008

adamrice: I've never heard it called "cowboy coffee" before. I've always called it Turkish coffee, though it's common all through the former Ottoman empire. That, of course, is where the word "coffee" originates (kahveh). It's nice and strong, very thick and usually very sweet. I have no idea how caffeinated it is, though, compared to other methods.
posted by robcorr at 11:41 PM on January 23, 2008

robcorr--Certainly Turkish coffee is made using the same general method, but as I understand it, you use coarse grounds for cowboy coffee and superfine grounds (often spiced) for Turkish coffee. There's definitely a difference in how the coffee tastes between the two, and how you consume it (in a big coffee mug vs a demi-tasse).

For that matter, there's a similar method in Mexico. And probably lots of other places I don't know about.
posted by adamrice at 7:07 AM on January 24, 2008