Author Topic: Stainless steel vs aluminum kettle?  (Read 5485 times)

Offline csu007

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Stainless steel vs aluminum kettle?
« on: March 05, 2012, 10:38:36 PM »
So i was just curious as to what type of a brew kettle everyone uses? I have seen that many people use a turkey fryer (Al) however, i have also heard the Al can react with the beer and give it off favors. I currently use a 5gal SS kettle and was considering a small kettle (for smaller batches) and was curious if i should buy a turkey fryer or just go to target and pick a SS pot?
“Sometimes when I reflect back on all the beer I drank, I feel ashamed. Then I look into the glass and think about the workers in the brewery and all of their hopes and dreams. If I didn’t drink this beer, they might be out of work and their dreams would be shattered. Then I say to myself, “It is better that I drink this beer and let their dreams come true than be selfish and worry about my liver.

Offline tschmidlin

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Re: Stainless steel vs aluminum kettle?
« Reply #1 on: March 05, 2012, 10:53:12 PM »
While it's true that beer can react with aluminum and cause off flavors, when it is in the kettle it is wort, not beer.  The pH of the wort is high enough that it does not react with the aluminum, it is fine as a kettle.
Tom Schmidlin

Offline csu007

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Re: Stainless steel vs aluminum kettle?
« Reply #2 on: March 05, 2012, 10:59:34 PM »
that makes sense.
“Sometimes when I reflect back on all the beer I drank, I feel ashamed. Then I look into the glass and think about the workers in the brewery and all of their hopes and dreams. If I didn’t drink this beer, they might be out of work and their dreams would be shattered. Then I say to myself, “It is better that I drink this beer and let their dreams come true than be selfish and worry about my liver.

Offline euge

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Re: Stainless steel vs aluminum kettle?
« Reply #3 on: March 05, 2012, 11:46:04 PM »
Stainless is tough and durable. Expensive but first class. Aluminum is about a third of the price. My 80qt is thick-walled aluminum and cost less than $100 with a lid. Had no trouble drilling into it for valve and thermometer.

And no problems with flavor whatsoever. John Palmer who is a metallurgist as well as the author of "How to Brew" says aluminum is fine for brewing. Not fermenting!

You could ferment in the stainless.
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Offline punatic

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Re: Stainless steel vs aluminum kettle?
« Reply #4 on: March 06, 2012, 12:04:52 AM »
In for a penny, in for a pound.  Stainless steel is well worth the investment (IMHO).

I have never brewed in aluminum.  It is much more reactive, chemically, than stainless steel.  That gives me pause...

I was fortunate enough to have a wife who gifted me with a Vollrath 10 gallon SS stockpot early on in our marriage.  That worked great for a long time, for 6-7 gallon batches.  Then I moved up to 10 gallon batches and started using a converted 1/2 barrel sanke keg for my brew kettle.

The 10 gallon stockpot makes an excellent "open" fermenter for my fruit beers and meads.

Go with stainless as soon as you can afford the investment.
« Last Edit: March 06, 2012, 12:06:58 AM by punatic »
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Offline hokerer

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Re: Stainless steel vs aluminum kettle?
« Reply #5 on: March 06, 2012, 07:30:08 AM »
and, while purely cosmetic, another reason my brew kettle is SS is that I can scrub it clean and get it nice and shiny after each use.  With AL, you need to leave that oxide layer so you can't do that and it always looks grungy to me.
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Offline bo

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Re: Stainless steel vs aluminum kettle?
« Reply #6 on: March 06, 2012, 07:37:06 AM »
Get yourself a cheap, 1/2 barrel, SS keg and convert it. I see them on Craigslist all the time. The handles at the top are very handy and it's made of heavy gauge steel. You can cut the top out of it to accommodate a lid that you can buy separately. Plus, someone else has already scratched it for you. :D

Offline realbeerguy

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Re: Stainless steel vs aluminum kettle?
« Reply #7 on: March 06, 2012, 08:01:18 AM »
I like Punatic ascribe to "buy once, cry once".  S/S keggle or pot will be more durable than aluminum.

On getting a keg from Craig's list, it's a good possibility that it's a keg that was never returned for deposit, and that's stealing.  Get a keggle from a reputable source or scrapyard.  Even better is one that is being de-commissioned direct from the brewery.








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Offline mabrungard

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Re: Stainless steel vs aluminum kettle?
« Reply #8 on: March 06, 2012, 08:09:20 AM »
There is another important factor in the selection of material type for kettles and that is heat transfer coefficient. 

Depending on how you are heating your wort and kettle, that should be an important factor.  I formerly heated my kettle on a gas burner.  An aluminum kettle has a far better coefficient of heat transfer than stainless steel.  That means that you will heat your wort quicker in a aluminum kettle. 

I just converted to an all electric brewery with my aluminum kettle now pierced with an electric water heater element.  Now that high coefficient of heat transfer is working against me by transferring more of the heat that I'm putting into the wort, out of the kettle.  I'll be insulating the exterior walls of the kettle to help reduce that loss. 

To summarize: use aluminum if you are heating on an external heat source like a burner and use stainless if you are heating the wort internally with an electric element. 

The other arguments regarding corrosion and durability are inconsequential in my opinion.  Both metals provide excellent service in wort contact and brewery usage.  Aluminum is excellent in brewery use as long as the metal gauge is thick enough.  My industrial pot certainly is!
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Offline richardt

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Re: Stainless steel vs aluminum kettle?
« Reply #9 on: March 06, 2012, 08:58:59 AM »
I have been thinking about electric brewing, too.

Isn't there a better way to conserve the energy, i.e. use a cooler (pro: it is already insulated) and use a smaller RIMS-type module to heat the liquor or the wort?  That way one wouldn't have to worry about heat loss through metal vessels.

Offline dak0415

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Re: Stainless steel vs aluminum kettle?
« Reply #10 on: March 06, 2012, 09:38:00 AM »
Isn't there a better way to conserve the energy, i.e. use a cooler (pro: it is already insulated) and use a smaller RIMS-type module to heat the liquor or the wort?  That way one wouldn't have to worry about heat loss through metal vessels.

I had an HLT using a 10 gal igloo cooler (round) with an element mounted in the side.  Worked fine.  I also have a RIMS setup for my mash tun, and use the RIMS to heat the strike water.  I think Martin was addressing the boil kettle design.  I have a couple of layers of reflectix around my keggle mash tun and that provides sufficient insulation as well as being removable for cleaning.
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Offline hopfenundmalz

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Re: Stainless steel vs aluminum kettle?
« Reply #11 on: March 06, 2012, 11:03:03 AM »
There is another important factor in the selection of material type for kettles and that is heat transfer coefficient. 

Depending on how you are heating your wort and kettle, that should be an important factor.  I formerly heated my kettle on a gas burner.  An aluminum kettle has a far better coefficient of heat transfer than stainless steel.  That means that you will heat your wort quicker in a aluminum kettle. 

Martin, I don't agree with this.  If you look at the Overall Heat Transfer Coefficient the conductivity of the metal is the lowest resistance in the circuit.  If you heat with fire, the gas to metal has the highest resistance, the liquid is the next highest.  If you run the numbers, there is negligable time difference.  I actualy ran a test for 2 pats I had that were the same size and geometry. One was SS and the other was AL.  The SS kettle got to a boil faster!  I expected the AL to be a little faster.  I think it was due to more bubbles in the AL acting as insulators (rougher finish) and more loss of heat through the side walls in the AL.

Aluminum will spread the heat better so you avoid hot spots. 

This explains what I am talking about.  The example is very good.
http://www.engineeringtoolbox.com/overall-heat-transfer-coefficient-d_434.html
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Offline BrewArk

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Re: Stainless steel vs aluminum kettle?
« Reply #12 on: March 06, 2012, 11:11:16 AM »
Not really scientific but, I've never seen aluminum in a commercial brewery.
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Offline hopfenundmalz

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Re: Stainless steel vs aluminum kettle?
« Reply #13 on: March 06, 2012, 11:16:04 AM »
Not really scientific but, I've never seen aluminum in a commercial brewery.

Commercial breweries use caustics and CIP systems.  That would remove the oxide layer after every brew.

I have an old copy of the Practical Brewer from 1947 or so.  They have pictures of Aluminum fermenters!  The text points out that those had cleaning considerations.
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Offline punatic

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Re: Stainless steel vs aluminum kettle?
« Reply #14 on: March 06, 2012, 11:39:05 AM »
There is another important factor in the selection of material type for kettles and that is heat transfer coefficient. 

Depending on how you are heating your wort and kettle, that should be an important factor.  I formerly heated my kettle on a gas burner.  An aluminum kettle has a far better coefficient of heat transfer than stainless steel.  That means that you will heat your wort quicker in a aluminum kettle. 

Martin, I don't agree with this.  If you look at the Overall Heat Transfer Coefficient the conductivity of the metal is the lowest resistance in the circuit.  If you heat with fire, the gas to metal has the highest resistance, the liquid is the next highest.  If you run the numbers, there is negligable time difference.  I actualy ran a test for 2 pats I had that were the same size and geometry. One was SS and the other was AL.  The SS kettle got to a boil faster!  I expected the AL to be a little faster.  I think it was due to more bubbles in the AL acting as insulators (rougher finish) and more loss of heat through the side walls in the AL.

Aluminum will spread the heat better so you avoid hot spots. 

This explains what I am talking about.  The example is very good.
http://www.engineeringtoolbox.com/overall-heat-transfer-coefficient-d_434.html

Heat transfer is also a function of wall thickness.  Aluminum pots are necessarily thicker.  What is gained in the k value is given back in dx sub w.
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