[Homeroast] Hybrid vac pots--blowing off steam

Andy Thomas adt0611 at yahoo.com
Mon Apr 5 13:25:22 CDT 2010





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From: Samuel Goldberger <sgold at sphere.bz>


 
> If the stem is forced deeper into the pot to draw up more water, the thin
> layer of water will boil away completely in a few seconds.

Actually, the amount of water that rises up the stem is not so much dependent upon the depth or the length of the stem as it is by the length of time the heat is applied to the bottom vessel. 

The amount of water that rises up has everything to do with the length of the tube. Once the level reaches the bottom of the tube, no more water can rise, regardless of the vigor of the boil.

> The borosilicate
> glass can withstand the soaring temperature, not the sudden inrush of cooler
> coffee (~200° F coffee Vs 300+° F) on the boiled-dry glass bottom.

That supposes that the heat is left on during brewing. But that would make for very lousy coffee; and the water would never descend. 

I leave heat under the brewer for about 1 minute after the ascent of the water to the funnel, then remove from heat . I believe this is common practice. It does not make for lousy coffee.

In fact, this descent comes about precisely because the lower vessel begins to cool, which in turn requires that the heat be removed.
This is generally after 2-3 minutes or more of cooling. The cooling creates a vacuum (hence the name). 

By that time, even an overheated glass vessel would generally have cooled sufficiently to withstand the descending coffee. 

Perhaps, but I wouldn't want to take that chance.

[snip]
On Apr 4, 2010, at 3:19 PM, raymanowen at gmail.com wrote:

[snip]


      


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