Trepsik Senior Member Joined: 20 Mar 2012 Posts: 3 Location: U of M Expertise: Just starting
Posted Tue Mar 20, 2012, 9:52pm Subject: Use of a Boiling stone in Vacuum Brewer
Hi, this is my first post on these forums. I am very new to specialty coffee brewing. Have recently taken an interest in Vac pot brewing. I am planning on building a mad scientist set up out of new lab equipment (my organic chem lab inspired me), i.e. boiling flask to beaker. I was looking at pictures of retail vac pots and I couldn't help but notice the small chain hanging down from the filter. My question is this; does this chain serve as a boiling stone to prevent super heating of the liquid? The design I will be using is essentially a balance brewer without the balance. Any owners of these on this forum, and if so do you make use of a boiling stone?
Posted Wed Mar 21, 2012, 7:28am Subject: Re: Use of a Boiling stone in Vacuum Brewer
Yes, it can serve the function of a boiling stone, even though that's not its main purpose.
Super heating of water can and does happen in vacuum brewers. I've had it happen and you only find out when you put the top globe in place prompting an immediate and violent boiling. It depends on how smooth the inside of the glass is and whether there is anywhere for bubbles to form (but you clearly know all about that from your question anyway).
One of my Cona brewers tends towards it happening, so these days I put the top globe in place straight away, only putting the coffee in after the water has risen and stabilised.
Cona brewers don't have that little bit of chain, but the stem of the top globe seems to prevent it from happening anyway.
Trepsik Senior Member Joined: 20 Mar 2012 Posts: 3 Location: U of M Expertise: Just starting
Posted Wed Mar 21, 2012, 8:29am Subject: Re: Use of a Boiling stone in Vacuum Brewer
Thank you for your replies. And yes, Keepitsimple, it was the preheating of the water, suggested by most people, prior to attaching the top globe that led my concern.
Posted Wed Mar 21, 2012, 9:29am Subject: Re: Use of a Boiling stone in Vacuum Brewer
Trepsik Said:
Thank you for your replies. And yes, Keepitsimple, it was the preheating of the water, suggested by most people, prior to attaching the top globe that led my concern.
Yes, I've always preheated the water before attaching the top globe. I've never has a problem with super heating and didn't imagine it was a real possibility. Maybe for the sake of safety I'll start attaching the top globe before heating.
Just because it happened to you doesn't make it interesting.
In theory, there is no difference between theory and practice. In practice, there is.
Posted Tue Apr 3, 2012, 7:27pm Subject: Re: Use of a Boiling stone in Vacuum Brewer
Strange coincidence: I had the super heating phenomenon happen to me soon after posting in this thread that it wasn't a concern (and never having had it happen to me before). Here's what happened:
I heat the water in a kettle, pour it into the bottom globe on a scale, then place it on the stove. No sign of bubbles like there usually are, so I turn up the heat (yeah, I know). I wait a little longer, but still no bubbles. Oh well, it's got to be hot enough by now, so I start to put on the top globe. As soon as the end of the chain hits the water, there is crazily violent boiling, but thankfully no actual explosion.
The sad thing is that I didn't immediately realize what was happening, despite just recently having been warned about it.
So my new method is to stick the funnel part way into the bottom globe immediately after placing it on the stove, so the end of the chain is in the water. Then, when I see the first signs of bubbles, I push the funnel all the way in so it seals. I then start adding the coffee when the water is about halfway up.
Just because it happened to you doesn't make it interesting.
In theory, there is no difference between theory and practice. In practice, there is.
alanfrew Senior Member Joined: 19 Dec 2001 Posts: 596 Location: Melbourne Expertise: Professional
Posted Wed Apr 4, 2012, 4:02am Subject: Re: Use of a Boiling stone in Vacuum Brewer
The easiest and simplest method method to avoid superheating (a problem with vacpot jugs that have been through the dishwasher) is adding a few grains (very small pinch) of ground coffee to the water in the jug. Instantly solves the shortage of nucleation sites.
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