This may be an equally bad idea (just brainstorming here), but what if instead of extending the tube closer to the bottom, you raised the floor closer to the end of the tube? If you had a flat plate or glass disk that could displace that last 1/2" of water or so. Would have to be heat resistant, and I'm sure there's a reason you can't do it. Probably the same reason they don't make these things with really thick bottoms to begin with, & a cutout only in the center where the tube extends, or tapers from thick on the edges to deeper in the middle to accomodate the end of the tube. THAT would leave only a tiny bit of water in there. Might take too long to heat though.
Easier to just compensate for the extra water by making it a little stronger.
Posted Tue Apr 3, 2012, 7:31am Subject: Re: Do you REALLY need to brew full capacity in a Siphon pot?
This may be an equally bad idea (just brainstorming here), but what if instead of extending the tube closer to the bottom, you raised the floor closer to the end of the tube? If you had a flat plate or glass disk that could displace that last 1/2" of water or so.
Thing is - you need a certain amount of water in the bottom to maintain the pressure and force water vapour up the tube. Make that amount too small and it won't work properly, or more importantly could run dry or overheat with unfortunate results. A lot of table top type brewers do have a spherical bottom globe, so by design they already minimise the amount of water remaining that doesn't go "up north".
I still think it's best to leave well alone and buy more brewers if you need different sizes ;o)
These are my thoughts exactly. I don't understand why you would need to updose since at the end of brewing, you'll end up with the correct coffee/water ratio. Why would you add more grounds, when the coffee that's brewing in the top globe will already be concentrated regardless of the volume you brew?
An example would be Aeropress brewing techniques where you brew a concentrate that you add water to. Some of these methods call for a 1/1 ratio which is FAR more dilution than vacpots produce. How is this any different?
calblacksmith Moderator Joined: 25 Nov 2007 Posts: 5,661 Location: Riverside, Ca, U.S.A. Expertise: I live coffee
Espresso: ECM Veneziano A1 Grinder: Many different commercial Vac Pot: 40s era Silex Drip: Milita, Bunn&Curtis... Roaster: Cast iron pan, gas burner
Posted Tue Apr 3, 2012, 10:40am Subject: Re: Do you REALLY need to brew full capacity in a Siphon pot?
Hey, try it and see. Do be prepared though to replace a brewer if you lower the volume of water in the bottom.
As touched on above, you need to maintain a constant pressure to the upper vessel. You also need to maintain enough of a heat sink in the lower globe to prevent the bottom of the brewer from overheating and breaking. The less water you have in reserve, the higher your chances of running dry and over heating and breaking the globe.
I can understand the desire for less than a full pot but I think that is the reason they are made in different sizes and that you always brew to the full pot as the reserve water is designed into the pot and how it is used.
It is your pot, feel free to try different things! Anything that is non toxic can be used to displace water in the globe if that is your desire, anything from marbles to ceramic pie weights, just watch the water level..... and have a little cash set aside.... just in case :D
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yakster Senior Member Joined: 25 Feb 2009 Posts: 1,006 Location: San Jose, CA Expertise: I live coffee
Espresso: Gaggia Factory / La Peppina... Grinder: Vario / Kyocera Vac Pot: Yama 8 + Pyrex Lox-in Rod Drip: Brazen / Kalita / Chemex /... Roaster: Behmor
Posted Tue Apr 3, 2012, 10:41am Subject: Re: Do you REALLY need to brew full capacity in a Siphon pot?
My experience has been that you don't need to brew at full capacity for good coffee. My primary siphon is the Yama 8 and it wasn't until recently that I started brewing at full capacity to satisfy the coffee horde at my house. My standard brew used to always be the lowest mark on the bowl, the 5 cup marking, and the coffee was just fine.
You've probably heard all the advise about needing a minimum level to brew with to get a good draw-down, etc., but bottom line, even though the volume of water the remains in the lower globe will be a higher percentage at a lower batch size, I still get good results. It is possible that you may see the effects on the coffee extraction if the coffee to water ratio during brewing is changed because the extraction is dependent to the gradient of solids being extracted from the coffee to the dissolved solids already present in the water, but my experience with the 5 cup versus the 8 cup has been that it's not that significant. I haven't measured extractions by TDS, however and I also use a fairly long, two minute immersion time. Scott Rao in his book Everything But Espresso advises that you fill the lower chamber at least 2/3 full when using immersion times shorter than two minutes to ensure sufficient vacuum for a reliable draw-down.
Posted Tue Apr 3, 2012, 11:40am Subject: Re: Do you REALLY need to brew full capacity in a Siphon pot?
I brewed at less than maximum capacity sometimes when I actually used my vacpot on a regular basis, and it never shattered/imploded. I guess I could test some things for you, since if something happens to mine it's not that big of a problem. I don't have a butane torch though, only an electric element.
Posted Tue Apr 3, 2012, 12:51pm Subject: Re: Do you REALLY need to brew full capacity in a Siphon pot?
I have a TCA-5D (20oz) and routinely brew with 14oz of water, no problem. I never tried this with my stovetop pot because the lower globe design allows more water to stay down during brew, which means there is less water up top for extraction, which could impede brewing. I think there's a threshold, where you can get away with maybe 75% capacity, but probably not 50% capacity. You need a good amount of water up top in order to properly extract the desirables from your coffee.
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