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Re: [new_distillers] aluminum pot

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  • Zapata Vive
    Pretty sure ZBob has made a lot of booze in aluminum pressure cookers and noted no faults, nor the oft cited pitting, unless something has cropped up in the
    Message 1 of 34 , Jul 26, 2013
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      Pretty sure ZBob has made a lot of booze in aluminum pressure cookers and noted no faults, nor the oft cited pitting, unless something has cropped up in the last year or two.

      I  just read a journal article "Corrosion characteristics of aluminum alloy in bio-ethanol blended" .  They found corrosion in up to 20% ethanol (highest percentage tested) after 24 hours at pressure and 100*C.  Lower temps showed no corrosion.  I imagine something more exciting is going to happen if you get a pressure cooker still with a 20% ABV charge up to 100*C

      I think at least so far as corrosion goes it would be sufficient to not let setback sit around in your cooker and rinse it out when your done.

      So far as off tastes go, I have no idea, but Zbob didn't mention it in Making Fine Spirits, where he endorses aluminum pressure cookers.

      All that being said, I've often eyeballed my 10 gallon All American 1941X and thought it'd make a fine boiler, but no way would I take even the smallest chance in a $700 pot!  Been meaning to try it for myself on one of my smaller PCs to work out fine details on test size batches, but I have trouble motivating myself to put in the hard work of small tests.

      So have ya'll actually tried it and seen pitting/gotten off tastes, or just heard about it?


      On Fri, Jul 26, 2013 at 11:52 AM, Jim Graves <jimbull34@...> wrote:
       

      The alcohol reacts with the aluminum and gives a very, VERY bad taste to it plus it errodes the pot!  Don't use, old pressure cooker were cast steel, the new ones ore cast aluminum, don't use 'um.



      From: captndan78 <captndan78@...>
      To: new_distillers@yahoogroups.com
      Sent: Friday, July 26, 2013 9:05 AM
      Subject: [new_distillers] aluminum pot

       
      What's the big deal with using an aluminum pot for a still? It is NSF approved. Pressure cookers are aluminum.




    • larryfitzpatrick2003
      Hi, (Short version: Aluminum oxides react with acids and facilitate alcohol oxidation reactions. Some of the byproducts of these reactions aren t so good.
      Message 34 of 34 , Nov 30, 2013
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        Hi,


        (Short version: Aluminum oxides react with acids and facilitate alcohol oxidation reactions. Some of the byproducts of these reactions aren't so good. Unless producing max-purity etoh, why not play safe and use anodized aluminum, which is non reactive?)


        Disclaimer: not a chemist, nor chemEng. These are reasoned opinions, that you may refute or extend.


        Newbie here who's done a bunch of reading on this subject, and can't find a whole lot of well-argued conclusions. But there is a lot of data. The key is to examine the reactivity of Al with all the compounds found in the wash. What those reactions can produced, whether they'll make it into the distillate, and whether the by products are healthy or not.


        Aluminum oxide (the surface) is pretty reactive and creates some nasty byproducts.


        The aluminum oxide formed naturally on the surface of the aluminum reacts with ethanol to produce ethene (ethylene).

        http://www.chemguide.co.uk/organicprops/alcohols/dehydration.html

        Ethene is pretty widely used, but isn't terribly great for humans.  But, the other alcohols in the wash will form other alkenes, by the same reaction. The boiling points of the alkenes are either well below or well above the range of etoh distallates.


        It seems that ethoxide and methoxide salts of alumimum can be formed, as well. These are hazardous substances. But in what proportion are they formed? And will they make it into the distallate? BPs are hundreds of degrees C.


        In acids with the presence of chlorine (is your water chlorinated)? Aluminum chloride is formed --http://www.chemguide.co.uk/inorganic/period3/oxidesh2o.html -- a neurotoxin. BP 120C but soluble in both ethanol and water. http://en.wikipedia.org/wiki/Aluminum_chloride


        Ketones, aldehydes, esters all participate in some reactions with aluminum salts. 





        ---In new_distillers@yahoogroups.com, <last2blast@...> wrote:

        In truth, we can't compare an aluminum engine to an aluminum pot for several reasons friction, heat, and constant exposure to ethanol under adverse conditions.  There is potential for low Ph levels to cause some eventual erosion of any metal over time, but the real question is whether that extremely small amount of trace metal can be transferred from pot to distillate?  FDA labels distilled water as purified for a very good reason, and if you distill properly there will be nothing but distilled water and ethanol in your jars.

        Robert


        From: Zapata Vive <zapatavive@...>
        To: new_distillers@yahoogroups.com
        Sent: Friday, November 22, 2013 10:11 AM
        Subject: Re: Re: [new_distillers] aluminum pot

         
        So the labs say aluminun is corroded by ethanol. But first hand use in our hobby reports minimal to nonexistant corrosion.  At that, the labs modeling car parts say the corrosion is formed by a reaction between ethanol and aluminum, forming aluminum ethoxide before drying.  BP for aluminum ethoxide? 320ºc, im not concerned, but we all choose for ourselves....
        On Nov 21, 2013 6:56 PM, "Wes" <yhetti@...> wrote:
         
        This has been well studied because of car engines.  Might be interesting:

        http://lmgtfy.com/?q=ethanol+aluminum

        Check out the two PDFs relation to corrosion properties.


        On Thu, Nov 21, 2013 at 6:38 PM, <tony.ackland@...> wrote:
         
        Matt - what evidence do you have of this ? What is formed ?

        Tony

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