Peppersass wrote:...Could be that I didn't stir after removing from the heat...
So it seems that the difference was placing the grounds in the globe before the rise instead of after. I've seen videos of the former, but have always done the latter. Could that really be the difference between clogging the filter and a normal draw-down?

BTW, I was impressed by the lack of coffee particles in the cup and the fuller body compared with the paper filter.

One variable at a time.

FWIW. I have used vacpots weekly for 8-9 years.
* I have never stirred, either during or after. I always push down with a rice paddle.
* I always put the coffee in after the water has ascended.
* I have draw downs of 1:15 for the 5 cup and 2:00 or so for the eight cup.
* I grind just a tad finer than a pourover.
* I shoot for a total extraction time of 3:15-3:20, including draw down

I could count on one hand the number of stalls I have ever had. No cooling cloth. Not boasting. Just telling what works consistently for me.

Richer, fuller body? The oils and proteins are permitted through.

Boldjava wrote: * I have draw downs of 1:15 for the 5 cup and 2:00 or so for the eight cup.
* I shoot for a total extraction time of 3:15-3:20, including draw down

So you steep for 1-2 minutes? That's quite a bit longer than I've done in my 3-cup with paper filters. I usually steep for 35-45 seconds, and the total time is around 2 minutes.

I have a 5-cup stove top Yama, too. I'll give the Cory rod a try in that, too.

Possibly the longer steep time is needed to create enough suction to draw the coffee back down. I use a silex rod with a silex pot, same grind as for pourover and steep for 1-1½ minutes. Total brew time including drawdown, about 2½-4 minutes.

Peppersass wrote:So you steep for 1-2 minutes? ...

Yes. I am shooting for 3:15-3:30 min total coffee/water contact.

No stirring, during or after. Out, stirring spoon, out.

A couple of thoughts here, with the 8 cup vac pots, longer contact times seem warranted, I wait two minutes before I remove the vac pot from the heat. I've heard that people who use smaller vac pots use shorter times but you'll want to have the contact time long enough to build up enough of a vacuum when you remove the heat that you get a good draw down. If you don't want to extend the contact time too much you can let the water rise into the upper funnel and wait a while for more water vapor to exit the lower globe before adding the coffee to help build up the pressure difference at the end. This is a good time to set the temps anyway for the kind of temp and agitation you want during the soak. I like it not too vigorous.

I favor adding the coffee after the water has started to rise to the top of the globe. This helps ensure that the water temps are where they should be and I always thought it helped with stalls. My biggest problem with stalls was my grinder. I had a Cuisinart when I started and upgrading to my Baratza Vario virtually eliminated stalls and greatly improved my coffee.

There's another technique that you may want to try to reduce the chances of stalls, the "Hoople Thurst" which was suggested by Doug Hoople on the old Sweet Maria's mailing list in 2009 which helped me when I was battling with this issue with my Cuisinart, I'll excerpt below:

Doug Hoople wrote: To keep the fines from clogging the glass filter, just before turning off
the burner to start the drawdown, turn the burner up to induce a high level
of turbulence in the funnel.

What I think happens is that the fines respond more vigorously to the
turbulence and get driven higher in the funnel, giving the boulders a
fighting chance of getting to the filter first. This is, in fact, precisely
the opposite of the vortex effect, in which the fines get driven down to the
filter first.

Whatever the reason, the "thrust" of turbulence right at the end produces
predictable drawdowns and appears to eliminate altogether the clogging
produced by fines reading the filter early. And, because it's right at the
end, the rise in temperature is limited and remains well within the desired
range.

You know, that makes sense. In an immersion brew, grounds seem to sink as the extraction process completes, which means that finer grounds fall out of the slurry earlier.

That's no big deal in an immersion brewing scenario. Or in a paper or cloth filtered siphon brew. But if you have a glass on glass filter interface, you are counting on coarse grinds building up and catching the fines. If too many fines build up early in the process, they will plug up that small gap between the glass surfaces.

Thanks for this tidbit. It explains why I've had some stalls recently even though I'm using a quality brew grinder (and have had no problem brewing at identical grind settings on other occasions). I'm not maintaining enough agitation in the slurry, which is allowing fines to build up at the glass rod early in the brewing process. Bingo

I'm also remembering that the few times I tried sifting with my old Cuisinart grinder and a vac pot that it seemed to make things worse rather than better.

Great stuff! Thanks.

Now I understand how the filter works, the role fines can play in creating a stall and how agitation can keep the fines off the filter. It makes total sense that a longer steep time with a little agitation can prevent a stall. Also, I wasn't thinking about the strength of the vacuum. I was just assuming it reaches max when the water has risen and didn't consider that it continues to strengthen for a while. I suspect my stalls were a combination of fines clogging the filter and insufficient vacuum.

My good results this mornings bear that out. Again, I put the coffee in at the beginning (I hadn't read the latest posts in this thread, so next time I'll try adding the coffee after the rise, but only after I've waited longer for the vacuum to build up in the lower globe.) Once a few large bubbles appeared in the lower globe, I inserted the top globe and adjusted the heat for a slow rise. I let the coffee steep a full minute before removing from the heat, which was about 30 seconds longer than last time. I kept the temperature high enough to maintain the vacuum but low enough to avoid too much gurgling. The draw-down took one minute, and I didn't have to use the cold, wet cloth to accelerate it. That's two minutes for steep and draw-down, but doesn't count the contact time during the rise, which I didn't record.

The extraction yield was slightly higher than last time -- about 19.5%. The taste was slightly under-extracted. I think an extraction yield of 20%-21% is probably right for the CCC Idido I'm using. It occurred to me afterwards that the glass rod may be letting a small amount of undissolved solids through, which increases the TDS reading, and the sample should be filtered prior to measurement with the refractometer. I'll do that next time.

I'm sure I need to get the extraction level up a bit. Probably the best way is to extend the steep time. Also, raising the heat before the draw down to agitate the brew vigorously and get the fines off the filter may help get a little more extraction yield.

I echo what multiple posters have said:

- I grind just a touch finer than I do for pourover.

- 2 minute brew time prior to removing from heat - gives a good extraction and elevates lower chamber temperature enough so that the drop is enough to make the vacuum needed to suck down the brew

- I always add the coffee once all water has gone to the top. I don't think doing the opposite helps in drawdown, but as the water slowly rises while the pot heats up, your beans are soaking in sub-temperature water.

- My drawdown starts about 30 seconds after removing from the fire, and lasts about 45 seconds.

Carl - I'd caution against walking away during the drawdown. Not sure if you do, but one of your posts gave me the impression you don't watch the drawdown. I'll echo the poster who said I can count my stalls on one hand, but one of those early stalls was an implosion. I lost a pot that way. There is probably nothing worse than that - you're all excited for your tasty cup of hand-crafted morning coffee, and now you have broken glass, coffee all over the counter and floor, and none for you to drink! Now, if I have a stall, I break the seal, make a mess all over the counter, but I save the pot. Rare event, but it is a pain to order a replacement carafe.

kaldi61 wrote:...
Carl - I'd caution against walking away during the drawdown. Not sure if you do, but one of your posts gave me the impression you don't watch the drawdown. I'll echo the poster who said I can count my stalls on one hand, but one of those early stalls was an implosion. I lost a pot that way. There is probably nothing worse than that...

Never had an implosion but have read of them. Guys blame it on a glass imperfection. I am not convinced.

You can boil them dry. Get busy with something else, have too little water in the bottom, commence to make the coffee, and boom! I didn't think I could run the bottom dry. Wrong. I have run them long intentionally with the globe on top and the residual water does boil <?>, evaporate <?>, or ascends to the heavens <?>.

I never walk away but the whole process is pure Zen to me so I am a bit transfixed and anchored to the stove.