Paranoid Campden Tablets Questions

[reuliss]

First, I've read AJ's awesome post on the step-by-step process for using campden tablets. I have two questions not addressed by that post, but that's not because AJ's post was in any way lacking in comprehensiveness. More that I'm just paranoid. So, here goes:

1. Does the temperature of the water to which you are adding the campden tablets have any impact on the chemical reaction? I like to draw scalding hot water into my HLT from my sink to save some time, but I want to make sure that the campden tablets will still do their job.

2. Does order matter? For example, if I were to fill my HLT, add campden tablet, stir and then later decide to add more water to the HLT, do I need to add more campden (assume that the size of the first dose was large enough to treat the combined volume)?

 

[ajdelange]

1. Arrhenius's rule of thumb is that the rates of chemical reactions doubles foe each 10 °C increase in temperature. If the metabite reaction follows the rule then increasing the temperature by 10 ° would cut the reaction time in half. As the reaction takes place pretty quickly in cold water there will be little benefit in raising the temperature from this POV. OTOH there is no reason not to do things at higher temperature except perhaps that the SO2 will tend to leave solution faster. It is the SO2 that does the job so perhaps it is better from that perspective to add Campden tablets at lower temperature.

2. If the dose of metabite added to the original volume is sufficient to treat the original volume plus any anticipated additions then no, no additional metabite is needed when such additions are made.

 

[SnakeRidge]

Off topic to the campden question, but you said you're paranoid....

Have you ever seen the inside of a hot water heater? Not pretty. I think in most instances the output of a hot water heater isn't even considered potable water (I could be wrong about that, but I wouldn't drink it). It's an attractive option to get a 30-40* jump on heating water, but something to think about.

 

[mabrungard]

AJ, at what temp is metabisulfite thermally decomposed? I'm just concerned that someone using this method at a near-boiling temp may not be achieving the full dechlorination expected.

Personally, I recommend that minerals and acids should be added to water at modest temperatures to avoid issues like above.

 

[hunter306]

Off topic to the campden question, but you said you're paranoid....

Have you ever seen the inside of a hot water heater? Not pretty. I think in most instances the output of a hot water heater isn't even considered potable water (I could be wrong about that, but I wouldn't drink it). It's an attractive option to get a 30-40* jump on heating water, but something to think about.

100% correct, unless you're running a tankless heater directly into your hlt, I wouldn't recommend pouring water from the HWH into your batch. That water is disgusting...

 

[reuliss]

Thanks for all of the responses. Given all of the points, I think it's better just to use cool water and work with that.

 

[ncbrewer]

Along the lines of paranoid campden questions, I wondered about sanitation of the water. I dissolve a campden tablet in 2 liters of tap water so that it can be divided among the water additions by volume. My last addition is top-off, so I always sanitize the water container with Star San before adding any water or campden. Since campden solution can be a sanitizer, I was wondering if the Star San treatment is necessary. My solution isn't strong enough to sanitize equipment, but maybe the campden water itself is sanitary. Any thoughts?

 

[ajdelange]

AJ, at what temp is metabisulfite thermally decomposed?

Not at or below boiling (I don't know what the actual decomposition temperature is). But as noted the hotter the solution the more SO2 will leave it and we want the SO2.

 

[ajdelange]

With respect to the use of water from a hot water heater: quite a few breweries (small startups) I've been in do this but there is a big difference between what they do and what happens in a typical house. In the brewery water is run through the heater in large volumes. It does not sit hot on the deposited minerals in the tank for days before it is being used. I'd say that if you want to use water from your water heater run the hot water to the drain or take a long shower before brewing so that you flush anything that has been standing out (water from the hot faucet comes out cold or cool). Then let the heater heat the new water to temperature and draw it for brewing immediately.

 

[reuliss]

AJ, Martin, we are all very lucky to have such valuable, generous resources. Thank you. I for one would be far behind as a brewer than I am now if you guys weren't so willing to share your expertise.