Using a Büchner Funnel

[Chris Amirault]

As I mentioned in the All about Bitters topic, I purchased this pump, Büchner funnel, filter paper and beaker set-up, and thought some others out there might find some detailed photos and notes to be useful. I've never used one before, so feel free to chime in with advice, corrections, and the like.

First off, the equipment. Here's the pump and filter papers:

The flask -- which for my purposes will be plenty big:

Funnel from the side:

Perforated funnel base:

More later tonight when I take a crack at filtering a few different things at home.

[lemon_twist]

Maybe you already know this:

Wet the filter paper after you pull vacuum but before you put in your bitters. This will prevent undesirables from going under the paper before it is sucked flat. I've never used a little pump like that before. Will you have to continously pump it the whole time you filter?

[Chris Amirault]

Thanks. That's one of the things I had assumed based on similar tips with other filters (coffee, stock), and it made a big difference. You don't have to pump continuously, as the pressure is only reduced a little by the liquid trickling down; about 10-15 pumps at the start, then 5-10 as needed, seemed to do the trick.

Here's the set-up ready to go.

I wasn't careful enough with the ceramic funnel and chipped a tiny sliver of glass off the beaker as I was preparing to wedge the funnel and stopper into the beaker. No crack, though, so it didn't have any effect on the function.

Here are the liquids I was filtering in their "before" state; even though i had poured off a lot, you'll see sediment and louche throughout. First, pineapple-infused rum:

Pineapple-infused Campari (for Toby Maloney's Riviera):

Hess house bitters:

John Deragon's grapefruit bitters:

Pimento dram:

Here's the funnel filled with pimento dram being filtered for the first time:

I started pumping away, getting a good strong flow, and as it slowed, I pumped harder and harder. Mistake. Here's the source of the great sucking sound you've heard so much about:

Basically, for the first filtering, it pays to take a bit of extra time. If you're in a hurry, it's easy to put too much pressure on the filter paper. I also learned that carefully pouring liquid off the top (instead of shaking it, say), letting that liquid filter first, and pouring in the louche and sediment at the end was a good idea; otherwise, that stuff sinks to the base of the funnel and impedes the action of the filter.

As you progress, the papers are, of course, covered with less and less sediment, which is a good indicator of how you're doing. Here's the pimento dram's penultimate filter:

There were big differences in the final filterings for each liquid. I focused on the pineapple-infused rum, as it was easier to see the results. Here it is after two filterings:

Pineapple-infused rum after four filterings:

The Hess house after four filterings was also very clear:

I didn't bother doing four filters for everything here, but that seemed to be the magic number. I've got a new batch of a Hess house bitters variation steeping, so I'll try to document that at each stage. The effects are quite drastic, as you can tell.

As for tips, it definitely pays to be patient and to resist the desire to increase the vacuum strength. Wetting the filter and pumping it a bit before adding the liquid you're filtering works well, too: you'll hear hissing noises that mean that there's a slight fold in the filter through which air is passing -- and thus through which the liquid could pass. Placing the filter directly in the center of the funnel and leveling the funnel are both good ideas, I found.

[C. sapidus]

Chris, we use a pump like that (with a reservoir attached) to clean up small mercury spills in the labs. One other way to generate vacuum is to attach an aspirator (click) to your faucet.

[MGLloyd]

Boy, that equipment sure takes me back to my chemistry days. Do you feel that you are only removing visual haze and sediment, or are you also removing flavor? I would be interested to know just how many flavor compounds are in the sediment that is being removed.

[Chris Amirault]

I can't quantify how much flavor I'm removing by filtering, but I don't think it's much. Certainly the bitters and pimento dram aren't suffering from lack of flavor, and the pineapple-infused liquors are both still wonderful.

As for the stuff filtered out, my guess is it's not going to have much flavor left, especially the fruits. I tried a few strawberries after infusing some tequila with them and straining out the hooch, and they were devoid of any strawberry flavor; the pineapple was better, but I think it's because some of the chunks had been pretty large.

Next time, it would be interesting to scrape up some of the filtering residue, rinse it off (no fair tasting the liquor left on it), and see what's what. I think stuff with volatile oils may still have some flavor left, unlike the fleshy, giving fruit.

Edited July 14, 2008 by chrisamirault (log)

[His Nibs]

On the tip of wetting the paper, I would use the base liquid that you infuse in rather than water. Water might 'crash' out some of the water insoluble organic materials.

Edited July 23, 2008 by His Nibs (log)

[Chris Amirault]

OK, will do -- but what does "crash out" mean?

[slkinsey]

"Crash out" = come out of solution as a precipitate.

This might potentially happen to some of the dissolved substances as the proof is drastically reduced where the solution contacts the water-soaked filter paper.

[Chris Amirault]

Got it. That makes sense.

I've done the first filtering series for a batch of bitters here, and still am grappling with having a weak spot give in the filter paper. It's pretty clear now and settling out a bit more louche. I'm going to try to do the last run in the next few days, will grab the camera when I do.

ETA: I did the scrape test and there's not much there. It's not without flavor, and the louche is sweet, but it's mainly just sort of muddy.

Edited July 24, 2008 by chrisamirault (log)

[Chris Amirault]

Update. I've filtered both a batch of house bitters and a makeshift batch of mole bitters to good effect. However, last night, my wife was cleaning up and tried to remove the hose from the side arm at the top of the flask where the hose connects. It sticks very tightly, and, well, Andrea broke it off. I'm going to order a new one but, yeesh, that damned flask is pretty frail.

ET add the proper "side arm" name.

Edited July 30, 2008 by chrisamirault (log)

[Chris Amirault]

Another update. I have a batch of jerk bitters steeping, and I took advantage of some ripe pineapples to infuse some rum in the fruit. When those are ready I'll filter them and take notes. Meanwhile, I noticed that the house bitters I've been building based on Robert Hess's formula got cloudy, and as Avery (BittermensAG) suggested no amount of filtering cleared them up. I'm letting them settle in hopes of pouring off the top. However, if anyone has suggestions for something I can do with this gadget to address the problem, I'm all ears.

[Kent Wang]

With the pineapple rum, are you just chopping the pineapple? Could you also puree it since you're going to filter it? You would get maximum extraction, though you would also end up with a lot of the juice and the attendant sweetness, which could be good or bad.

Wouldn't this also be good for making a bisque, where you take shrimp (crawfish, or lobster) shells, blend them, boil and then put them through the funnel? Basically, any application where you would otherwise use cheesecloth and press? Or is this just as time consuming?

[Chris Amirault]

It's a matter of preference. If you puree the fruit you get a watery product, I think, so I go with chunks that can then be used for other applications (pineapple upside-down cake, e.g.) since it's retained more juice.

[Hassouni]

Resurrection time:

 

Do you find that it drips quite slowly? I just got my setup and tested it out tonight. After a few minutes it's drop by drop. To do about 300ml took well over half an hour, but then my stuff had a LOT of gunk in it....

[MelissaH]

If you have a lot of gunk, is there any way you can pre-filter to get at least some of it out?

 

Back in my synthetic organic chemist days, it was pretty rare for us to filter through a Buchner funnel with a paper. When we were working up reactions, a very common last step before purification was to add a powdered drying agent and swirl it around. It would suck up any last bits of water or aqueous solutions. Then to get rid of the drying agent, we'd send the whole thing through a fritted funnel topped with a layer of Celite (diatomaceous earth). The Celite wouldn't clog as quickly as a filter paper would, and if it did it was easy to scrape off the top bit with a metal spatula and clear out the filter bed. (Side note: home beer brewers live in dread of a stuck mash: when the grain bed clogs up and the water can't flow through. The classic homebrew solution is to add some rice hulls to the mash grain. The rice hulls act sort of like the Celite, sort of like a pre-filtration, to catch the fine stuff that can gum up the rest of the works.) Anyhow, when we'd dried and filtered the solution, we'd pop it on the rotovap to remove the solvent, sometimes pump on it with a vacuum to make sure all the solvent was gone, and then purify our compound by some appropriate means.

[Hassouni]

Well, a fine mesh strainer doesn't help, and a coffee filter hardly works. I figure as far as relatively budget friendly option goes, it was that or gelatin.

 

 

ETA: I should have mentioned I was a filtering a liqueur, so maybe the sugar had something to do with it.

Edited September 11, 2014 by Hassouni (log)

[huiray]

There are different grades of filter paper with different porosities.  The clogging of Whatman#1 with fine particulates is a common phenomenon in the lab, heh.  How about a sintered glass funnel (I'd go w/ M porosity) plus a bed of celite, prewetted and tamped down with a spatula or (preferably) a glass rod made so that it has a flattened end? Highly aqueous solutions would tend to mess up the celite, though, so high-proof (high alcohol) stuff would work better.  (Of course, in this case the use of anhy. MgSO4 or Na2SO4 etc would not be advisable because these would be aqueous solutions... :-) )

Edited September 11, 2014 by huiray (log)

[BillBuitenhuys]

Hassouni, have you tried lining the fine mess strainer with a few layers of dampened cheesecloth as an initial filter?

[gfweb]

Well, a fine mesh strainer doesn't help, and a coffee filter hardly works. I figure as far as relatively budget friendly option goes, it was that or gelatin.

 

 

ETA: I should have mentioned I was a filtering a liqueur, so maybe the sugar had something to do with it.

Its on a vacuum flask, right?

[Hassouni]

Hassouni, have you tried lining the fine mess strainer with a few layers of dampened cheesecloth as an initial filter?

I have not...

 

Its on a vacuum flask, right?

Indeed, with most of the air sucked out