How long for a campden tablet to take effect?

Discussion in 'Beginners Brewing Forum' started by The Green Man, Sep 13, 2018.

  1. The Green Man

    The Green Man Active Member

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    Hello Brewers, In my latest brew I want to use a campden tablet to make sure the water is free of chloramine and free chlorine. I'm reading conflicting advice on how long to add the campden tablet (1/2 a tab in my case) to my water. I thought it had to be left overnight, but then some have said it's effective almost immediately.
    Any advice / thoughts on this? Would be grateful for any light on the subject.
     
  2. Ozarks Mountain Brew

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    as soon as its dissolved it happens immediately, I crush mine into powder
     
  3. thunderwagn

    thunderwagn Well-Known Member

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    Same here. I crush and add. You can actually smell it off gas a bit.
    Chlorine dissipates very quickly. If you leave brewing water out overnight, most chlorine (if that's what your municipality is actually using) would dissipate on its own.
     
  4. The Green Man

    The Green Man Active Member

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    Thanks guys. The less hassle the better. Crush and go, job done.
     
  5. Hawkbox

    Hawkbox Well-Known Member

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    I tend to fill my water the night before and hit it then, just to be really really sure.
     
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  6. Nosybear

    Nosybear Well-Known Member

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    Campden works for both chlorine and chloramines effectively immediately. No need to wait.
     
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  7. Hawkbox

    Hawkbox Well-Known Member

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    How can it work immediately though? Does it go hunting chlorine? Does the chlorine rush to it? Otherwise there needs to be either some time or agitation to get the chemicals to react to each other. (I'm not saying it won't happen quickly, I just have serious doubts about it being immediate)
     
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  8. Yooper

    Yooper Administrator
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    No, it's an instant chemical reaction.

    If you want to go down the rabbit hole: https://www.homebrewtalk.com/forum/threads/campden-tablets-sulfites-and-brewing-water.361073/
     
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  9. Nosybear

    Nosybear Well-Known Member

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    Effectively immediate, meaning it takes a finite amount of time too small for you to measure. And yes, you stir it it. When I run my water, I can smell the chlorine. I add meta, stir, and the smell is gone. Yes, it's that fast.
     
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  10. Hawkbox

    Hawkbox Well-Known Member

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    Ah ok see, no one has ever told me you stir it. Everyone just says drop a campden tablet in and boom! Magic!

    Which was to good to be true.
     
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  11. The Green Man

    The Green Man Active Member

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    Aaah, the magic of Monsieur Campden! As always, I am in awe of the knowledge presented here.
    I have to say, I was with Hawkbox in the doubters camp. I had serious problems believing that it could feasibly be immediate. It appears I was wrong. I won't go down the rabbit hole though, I'll just take your words for it. :)
    Thanks all.
     
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  12. White Haus Brews

    White Haus Brews Active Member

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  13. Yooper

    Yooper Administrator
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    Ha- I was contemplating trying to copy/paste the whole chemical reaction but that's overkill, even for me.
     
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  14. Nosybear

    Nosybear Well-Known Member

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    Here you go:

    Sodium metabisulfite (SMBS) initially reacts with water to form sodium bisulfite (SBS): Na2S2O5 + H2O --> 2 NaHSO3
    Next, SBS reacts with hypochlorous acid to form byproducts free from free chlorines: 2 NaHSO3 + 2 HOCl --> H2SO4 + 2 HCl + Na2SO4

    You wind up with sulfuric acid, hydrochloric acid and sodium sulfate.

    Here's information on the dosing:

    While theoretically about 1.5 ppm SMBS will neutralize 1.0 ppm chlorine, typically 1.34 ppm is needed but 3.0 ppm SMBS per 1.0 ppm chlorine is used to account for incomplete mixing.

    So if we're using 40 liters of water for a batch (somewhat over 10 gallons), we would need 3 ppm (mg/l) * 40 l, or 120 mg sodium metabisulfite to treat 40 liters of water at 1 ppm chlorine/chloramine. Our water administration adds an average of 1.73 ppm of chloramine and 0.0673 ppm of chlorine dioxide, I'll round to 2 ppm chlorine, so I can safely say that 230 mg of sodium metabisulfite would dechlorinate my 40 liters of water.

    Dow Chemical states the reaction is rapid, but be sure and mix thoroughly.

    Good stuff, metabisulfite, it gives you a bit of pH drop through sulfuric and hydrochloric acid and a bit of sulfate through the sodium sulfate produced.
     
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  15. Hawkbox

    Hawkbox Well-Known Member

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    I think the thing that should be clarified in general is the mixing thoroughly. I just keep seeing people saying put a campden tablet in and it's instant.

    Personally when I see that statement it implies to me I don't have to take extra steps... like stirring.
     
  16. Ozarks Mountain Brew

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    that's why I crush mine and recirculate the water at high speed while it's heating, I start out with 20 gallons in my HLT, by the time it reaches 162F the water is free from off flavors
     
  17. Hawkbox

    Hawkbox Well-Known Member

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    And that makes sense. Now that I know that I will, but it never made sense to me before.
     
  18. thunderwagn

    thunderwagn Well-Known Member

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    Guess I've personally never given it much thought. I add it to all my brew water and by the time it's used for mashing and sparging, unless you were purposely not trying to mix, it would mix sufficiently on it's own. Chlorine is nasty stuff, but up against a few things, it does have weaknesses. Being exposed to air, heat, campden tablets...
     
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  19. Texas Ale Works

    Texas Ale Works Active Member

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    What is this "stirring" you speak of
     
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  20. Nosybear

    Nosybear Well-Known Member

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    I'd have thought that stirring wouldn't need to be called out.... Seems rather obvious to me that when you add chemicals to water that you'd stir to get a uniform solution. Did anyone mention crushing the tab to help it dissolve quicker?
     

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