# Potassium metabisulfite solution mix ratio?



## zxert

I'm extremely confused about how much pot-met to mix with water to make one gallon of sanitizing solution!

I've seen anywhere from 1/4 teaspoon to five tablespoons!

Can anyone clear this up for me?

Thanks!!


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## Sacalait

Three table spoons per gallon.


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## zxert

Thanks!

Wonder why the large disparity . . .


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## oldwino

Many wine makers use potassium metabisulphate for cleaning. I use one step because I get lazy. Using one step I don't have to rinse afterwards. However, after I clean a carboy and get ready for it to be stored for later use I throw in a few whole campden tablets, pour in a couple cups of water and cork the carboy. Swirl it around a little and put under the counter for storage. I clean with one step when I am ready to use it again. 

All tools, corks, airlocks, wine thiefs etc. get soaked in one step before they go into my wine.

However these are only personal preferences. There is a whole lot of ways to clean everything. I have well water and all of the water in the wine room is bottled water. I use less water with one step, no rinse.


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## Wine4Me

Just wondering here what does this do??
[I throw in a few whole campden tablets, pour in a couple cups of water and cork the carboy. Swirl it around a little and put under the counter for storage. I clean with one step when I am ready to use it again. ]


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## Luc

oldwino said:


> Many wine makers use potassium metabisulphate for cleaning.



Oldwino I think you are mistaking.

Pot-meta is not a cleaning solution.
The strong solution is used for sanitsing your materials, bottles, hoses, racking canes etc.
It will not make things completely sterile but will kill enough bacteria to not contaminate the wine.

The smaller amount (like a campden tablet) is used for keeping the wine healthy and prevent it from oxidising.

For cleaning use something like soda ash or any cleaner and rinse will afterwards.

Luc


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## Wade E

1/4 tsp is for killing off wild yeast and micro organisms in a new 5-6 gallon batch of wine that has not had yeast added yet. 3 tbls is the desired ratio per gallon for making a sanitizing solution.


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## seminarian

here's a question. Should one take some of the meta solution for sanitizing and put in a spray bottle, so if you open your primary fermenter, or carboy should you spray it down with the meta to protect your wine? I saw this done recently and am wondering if this is standard procedure?


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## Wade E

I always have a spray bottle full of the sanitizing solution but dont recommend spraying any in a fermenting vessel with a wine in there fermenting. Just sanitize anything that you plan on sticking in there or for sanitizing a primary bucket before adding your must to it. Everything must be sanitized before it touches your wine but you dont want to be sanitizing a fermenting wine.


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## zxert

Thanks for the input everyone, that cleared it up.


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## seminarian

wade, 

what actually was being done was the meta was being sprayed around the areas that got touched and opening the container where potential bacteria could develop.


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## Wade E

Depending on the size batch you are doing sparying some of that sanitizer in the primary could be lethal to your yeast. I would spray a paper towel with it and then wipe it, not spray it in there. Thats my opinion at least.


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## arcticsid

ZX, I,m pretty new to all this myself, but I use a one step my self. I use it a little stronger than recomended, but I wash and rinse and then "hit" my equipment again. Don't know for sure if it's the right way, but seems to work. I heard a couple makers using an "OXY-Clean", rinsing, and than follow with a one step, or other type of sanitizer. (oxy-Clean with NO CHLORINE!!!). Any thoughts from anyone else? I learned the two most important steps in here ZX, sanitize and patience. Good Luck, Troy


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## Wade E

one step is a cleaner , not a sanitizer! Oxy-clean is also a cleaner and not a sanitizer. Pot. Meta, sod. Meta, Star San, and Iodophor are sanitizers.


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## AJ-123

Metabisulphite powder in a spray bottle or other water solution will quickly "gas off" and lose it's santizing capability in a day, two, or three. Maybe in sealed bottle it will stay effective for a little longer. I'd mix it into water only immediately before using. It should also stay sealed (either tablets or powder form) as much as possible. The very wide range of effectiveness (or lack) of campden tablets which have been stored is a well known problem.


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## my wine

Winemaker School » How To Make & Use A Sulphite Solution







winemakerschool.com





1. Dissolve 50 grams (3 tablespoons) of metabisulphite powder in 4 litres (approximately one gallon) of cool water.
2. Submerge or spray all pieces of equipment with solution.
3. Rinse thoroughly with cool water and drip dry. You can store leftover sulphite solution for two months in a tightly sealed container.


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## balatonwine

my wine said:


> Winemaker School » How To Make & Use A Sulphite Solution
> 
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> winemakerschool.com
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> 1. Dissolve 50 grams (3 tablespoons) of metabisulphite powder in 4 litres (approximately one gallon) of cool water.



Same formula as found in Jeff Cox's 1999 book "From Vines To Wine". Yes, I have a copy.


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## jgmillr1

my wine said:


> Winemaker School » How To Make & Use A Sulphite Solution
> 
> 
> 
> 
> 
> 
> 
> winemakerschool.com
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> 
> 
> 
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> 1. Dissolve 50 grams (3 tablespoons) of metabisulphite powder in 4 litres (approximately one gallon) of cool water.
> 2. Submerge or spray all pieces of equipment with solution.
> 3. Rinse thoroughly with cool water and drip dry. You can store leftover sulphite solution for two months in a tightly sealed container.


This misses the fact that sulfites are more effective at low pH. (The same reason more sulfites are needed in wine at higher pH).

Mix in citric acid at a ratio of 2:1 and the sanitation will be better due to the lower pH and higher SO2 concentration in the solution.


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## bstnh1

my wine said:


> Winemaker School » How To Make & Use A Sulphite Solution
> 
> 
> 
> 
> 
> 
> 
> winemakerschool.com
> 
> 
> 
> 
> 
> 1. Dissolve 50 grams (3 tablespoons) of metabisulphite powder in 4 litres (approximately one gallon) of cool water.
> 2. Submerge or spray all pieces of equipment with solution.
> 3. Rinse thoroughly with cool water and drip dry. You can store leftover sulphite solution for two months in a tightly sealed container.


There is no need to rinse. According to Tim Vandergrift, after a couple of minutes the amount of sulfites is negligible. He has stated that he never rinses k-meta from anything. I have never rinsed anything.


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## balatonwine

jgmillr1 said:


> This misses the fact that sulfites are more effective at low pH. (The same reason more sulfites are needed in wine at higher pH).
> 
> Mix in citric acid at a ratio of 2:1 and the sanitation will be better due to the lower pH and higher SO2 concentration in the solution.



The ratios suggested in the formula account for a solution of tap water assuming neutral pH. So that is already built in. If you think of it for a second, 50 g of KMeta in 4 liter is actually a hell of a lot. So it is more then enough to get enough into solution** for the purpose at an assumed neutral pH.

That is, sulfites are not "more effective" at low pH, except in a relative sense to the amount added. That is, at lower pH one only simply needs to add less KMeta at lower pH for the "same" effectiveness that if the pH is higher. And thus, a lot of KMeta at higher pH can be as equally effective as less KMeta at lower pH. There are plenty of tables and formulae around about how much KMeta you need to add to get *equal effectiveness* at *each* pH. So, no, it does not "miss the fact".

If you want to use less KMeta, then yes, adding citric acid is a good idea. But if one uses this as a final rinse, before adding wine, I personally would not want to add any citric acid to the wine in any amount. But that is just me of course. To each their own.

** But I admit, getting KMeta into solution in tap water does require a bit of time and effort....


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## balatonwine

bstnh1 said:


> There is no need to rinse. According to Tim Vandergrift



"According to" someone is not really of much use. Anyone can say anything. According to me, you should rinse***. Can you provide an independent reference and data to support this claim*****? That would help validate the statement.

*** See how easy that is to say without a reference? 

***** And referencing Tim Vandergrift alone is not good enough for me... _argumentum ab auctoritate_


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## jgmillr1

balatonwine said:


> If you want to use less KMeta, then yes, adding citric acid is a good idea. But if one uses this as a final rinse, before adding wine, I personally would not want to add any citric acid to the wine in any amount. But that is just me of course. To each their own.


We are each free to make our wine however we want. Mixing in citric with meta is a standard industry method. I would have concerns with the large amounts meta pitting my stainless and hardening rubber gaskets that will leak later. Hence I will augment the meta with citric.


balatonwine said:


> Can you provide an independent reference and data to support this claim


Citric and meta are both food grade.


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## vacuumpumpman

jgmillr1 said:


> We are each free to make our wine however we want. Mixing in citric with meta is a standard industry method. I would have concerns with the large amounts meta pitting my stainless and hardening rubber gaskets that will leak later. Hence I will augment the meta with citric.
> 
> Citric and meta are both food grade.



I am also afraid if I just use meta alone that the residue will increase my overall SO2 value after bottling. I see how much residue is left over and that is the main reason why people want to rinse prior to bottling or putting their wine back into that vessel.


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## balatonwine

jgmillr1 said:


> We are each free to make our wine however we want.



Absolutely. I completely agree. The art of wine making. Goes without saying... even if I have said it before.... . 



jgmillr1 said:


> Mixing in citric with meta is a standard industry method.



True. But industry also has to deal with OSHA (or other national equivalents). And adding KMeta to a very acidic solution produces a lot of SO2, which can come out of solution as a gas. Which is toxic. So proper methods need to be used to prevent exposure to this toxic gas with acidic KMeta solutions. And if you have ever worked in industry, and had OSHA come down on you, you know they can come down like a ton of bricks if you get it wrong. So Industry is very careful how they use such solutions.

Which is why you see the "neutral" pH solution at web sites in or published books. Not only is it easier to use, it is safer (ergo these publications are trying to avoid liability issues). Especially for the home wine maker who may not be so careful with the solutions they use.

That is, it is one thing to deal with a demijohn or similar small container in an open space, but if you have to clean a vat from 60 L up to 200 L like I have, which may need bending into the container to scrub it out, you may encounter quite a layer of toxic SO2 layer in that large container if you use a more acidic KMeta solutions (been there, done that, was not pleasant). And not every home wine maker knows or is aware of that risk. Quite frankly, that is why I now use other cleaners for standard tank cleaning. Only use the pH neutral solution of KMeta as a bottle rinse before bottling.

Hope this helps.


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## balatonwine

vacuumpumpman said:


> I am also afraid if I just use meta alone that the residue will increase my overall SO2 value after bottling. I see how much residue is left over and that is the main reason why people want to rinse prior to bottling or putting their wine back into that vessel.



I rinse bottles with a Kmeta solution at bottling specifically to add the correct amount of KMeta to the wine at bottling.

That is, from experience and measurement I know how much wash solution I "loose" while washing bottles (i.e. the amount of KMeta solution left in each bottle after brief draining). Ergo, from that, and from knowing how much KMeta I need to add before bottling (and correcting for pH of the solution and the wine) I can simply wash with an appropriate KMeta solution to bring the bottled wine up to the necessary ppm that I want. Simple. Easy to do at bottling. This can be confirmed by opening a bottle in a few weeks and re-testing. Takes a bit of time and experience (and yes, I made mistakes), but after 20 years, I kind of got it figured out now (combination of both the art and science of wine making....).


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## Rice_Guy

@balatonwine ,,, good analysis on post #20. To me the key was to see that there was an ionization constant Ka in the very acid range, therefore to get the good stuff SO2 it is useful to make this an acidic solution. anyway since ppm concentration also pushes the reaction, ,,, it really doesn’t matter.


bstnh1 said:


> There is no need to rinse. According to Tim Vandergrift, after a couple of minutes the amount of sulfites is negligible. He has stated that he never rinses k-meta from anything. I have never rinsed anything.


I would not worry about rinsing in the home environment. If I drain and 5ml (1 tsp) remains (drains after dumping) in the bottom of a 5 gallon glass or PET carboy the dilution is 0.026%. I can’t even measure the effect of this quantity of SO2 in a full carboy therefore ignore it in calculations of added meta. 
In the industrial environment/ stainless steel tanks I would rinse any time there is some time between transfers. K meta is extremely corrosive on metals. In the factory I would always rinse, just in case the tank sat for a day.


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## Rice_Guy

It would be useful to see your data. ,,,, I have had a project in the back of my mind of monitoring SO2 after typical home processes for basic types of wine, Most of our vinters club members don’t test SO2 and those that do test mainly do it at racking.
My gut feel from testing so far is reds are fairly stable but whites and country wine eat up the SO2.


balatonwine said:


> I rinse bottles with a Kmeta solution at bottling specifically to add the correct amount of KMeta to the wine at bottling.
> 
> That is, from experience and measurement I know how much wash solution I "loose" while washing bottles (i.e. the amount of KMeta solution left in each bottle after brief draining). Ergo, from that, and from knowing how much KMeta I need to add before bottling (and correcting for pH of the solution and the wine) I can simply wash with an appropriate KMeta solution to bring the bottled wine up to the necessary ppm that I want. Simple. Easy to do at bottling. This can be confirmed by opening a bottle in a few weeks and re-testing. Takes a bit of time and experience (and yes, I made mistakes), but after 20 years, I kind of got it figured out now (combination of both the art and science of wine making....).


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## jgmillr1

The acidified meta mix is not only an effective sanitizer but also neutralizes the sodium hydroxide caustic cleaning solution I use.



balatonwine said:


> True. But industry also has to deal with OSHA (or other national equivalents). And adding KMeta to a very acidic solution produces a lot of SO2, which can come out of solution as a gas. Which is toxic. So proper methods need to be used to prevent exposure to this toxic gas with acidic KMeta solutions. And if you have ever worked in industry...


Yes, I have worked in OSHA regulated industries and currently work in the wine industry as winemaker and winery owner. The SO2 compressed gas cylinders are what you need to watch out for, not acidified sulfites.

I agree that the publishers will tend to couch their advice with cautionary statements to avoid liability. This explains Cox's further advice to ventilate the room.


balatonwine said:


> That is, it is one thing to deal with a demijohn or similar small container in an open space, but if you have to clean a vat from 60 L up to 200 L like I have, which may need bending into the container to scrub it out, you may encounter quite a layer of toxic SO2 layer in that large container if you use a more acidic KMeta solutions


I use the acidified mix when I sanitize my 2000L tanks. Yes, the SO2 can be strong. I have chemical air mask filters I can use but have not found the need. Note Jeff Cox's comment about using the sulfite-only solution on stainless below.


balatonwine said:


> Same formula as found in Jeff Cox's 1999 book "From Vines To Wine". Yes, I have a copy.


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## balatonwine

jgmillr1 said:


> Yes, I have worked in OSHA regulated industries and currently work in the wine industry as winemaker and winery owner.



Wonderful that you are an expert and a professional. Good to know.



jgmillr1 said:


> The SO2 compressed gas cylinders are what you need to watch out for, not acidified sulfites.



That time I had to take a break once when simply added KMeta to a 300 L vat of must, coughing and hacking by getting too much SO2 upon addition, basically says my personal experience is different. 

Oh, I know what I did "wrong", after the fact (in short, I got careless -- a common cause of accidents, at the home and in industry). A learning experience. But that is kind of the point.... A lot can go wrong that one may not expect. Especially if all the right conditions are met. Which may align more often with home DIY projects trying new things, and possibly being not fully informed of possible issues at forum discussions. Even by experts who may see many precautions as so "routine" that it does not merit mention, or think at an industrial scale, not at a bench level scale. And that a DIY may not even think about as being need to be done, and which can actually end up causing themselves damage if not done. Been there myself. Sometimes I was too much an expert in my field, that I missed informing a layman of what to me was an "obvious" point. I had to learn, there are no "obvious" points.



jgmillr1 said:


> This explains Cox's further advice to ventilate the room.



Oh, yes. I forgot to mention... the above SO2 issue to me happened outside. So Jeff Cox also missed a different obvious** that caused me to fail in my case. 

In short... Bad things can happen anywhere. And in unexpected ways. The best defense if a good offense, and a good offense is to try to avoid when things may go wrong if possible, but if not possible to be fully informed of what may happen so one can take rapid and corrective measures. And since you work in Industry, I trust I am preaching to the Choir here.

** I took a lot of chemistry in college. I know what I did wrong. And called myself an idiot right afterword, because I knew better. Kind of like...



Again, I just got careless. But it was a mistake anyone could make, especially one who was not aware of what could happen.



jgmillr1 said:


> Note Jeff Cox's comment about using the sulfite-only solution on stainless below.



I don't have SS. And I find this rather simple to make mix ratio is rather mild in its SO2 release compared to more acid solutions that are more likely to be not prepared correctly and may release more SO2.


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## CDrew

zxert said:


> I'm extremely confused about how much pot-met to mix with water to make one gallon of sanitizing solution!
> 
> I've seen anywhere from 1/4 teaspoon to five tablespoons!
> 
> Can anyone clear this up for me?
> 
> Thanks!!



LOL-I'm sure you're even more confused now! There is no doubt that a lower pH makes for a more effective metabisulfite solution. It's a better living through chemistry thing. More free SO2 = more killing power. But also more toxicity if you happen to inhale the fumes from your spray bottle. Me, I like 2 tablespoons of KMBS and 1 tablespoon of citric or tartaric acid per gallon. This is effective, cheap and concentrations are so low that no rinsing is needed or desirable. Just drain and use. I mix just before use and discard usually the same day any unused amount.

But as you can tell from the discussion in this thread, ALL reasonable amounts of KMBS with or without something to lower pH will work to kill undesirable winery bacteria and yeasts. But it will be more effective at a lower pH.

With that said, I would recommend you use the KMBS solution only for a final bottle rinse. (and also for barrel care but that's another story) For all other sanitizing chores, StarSan is a safer, better, and non toxic choice. It comes in a clever container with a measurement device built in. It's also easy to mix and use, very effective, and you could swim in a solution of it if you chose to. And if you use distilled water to make up your solution, it remains good for months.

You guys realize this thread is from 2008! The info is still relevant though.


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## justsipn

I’m very glad I read this thread. But, have to admit, I’m disappointed. 

I’ve been mixing a gallon, putting it in an old distilled water jug and filling a spray bottle when it gets low. Then just using the spray bottle to spray stuff down when needed. 

Now, I read that I’ve been probably using worthless solution all this time. 

If I have to mix up even a half gallon every time I need to do something like checking SG, that’s a lot of wasted K Meta.


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## jgmillr1

justsipn said:


> just using the spray bottle to spray stuff down when needed.


This what I (and other wineries) do and it works well. I mix up a couple gallons or so with the citric/meta mix and store it in an acid friendly sprayer. I'll work through it over a month, more or less.

The evolved SO2 gas is noticeable and a way of letting your nose tell you the solution is doing its job. I don't know how long the meta-only solution lasts, but I'd guess just as long.

At the end of the day, your goal is to sanitize the equipment. That means sufficient contact time with a sufficiently strong sanitizer. This is data which I don't have though. If anyone has a reference to a study on sanitation effectiveness, please post. 

For things I can soak, I use iodophor. That at least has a published working rate of 2 min when mixed at the right concentration. Even the health department approved of it.


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## justsipn

jgmillr1 said:


> This what I (and other wineries) do and it works well. I mix up a couple gallons or so with the citric/meta mix and store it in an acid friendly sprayer. I'll work through it over a month, more or less.
> 
> The evolved SO2 gas is noticeable and a way of letting your nose tell you the solution is doing its job. I don't know how long the meta-only solution lasts, but I'd guess just as long.
> 
> At the end of the day, your goal is to sanitize the equipment. That means sufficient contact time with a sufficiently strong sanitizer. This is data which I don't have though. If anyone has a reference to a study on sanitation effectiveness, please post.
> 
> For things I can soak, I use iodophor. That at least has a published working rate of 2 min when mixed at the right concentration. Even the health department approved of it.


Thanks for the information. But, earlier in this thread there's a post that says the K Meta will "gas off" within a day or two and become useless. Is that not true?


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## Rice_Guy

if the solution does not burn the nose it is useless
if the solution burns the nose/ makes you cough/ (could kill you) it is still active (the active portion is the SO2 gas as @jgmillr1 buys for his winery not the 99.97% that is a salt solution in water)


justsipn said:


> Now, I read that I’ve been probably using worthless solution all this time.


step back a minute, we put meta in a wine and it lasts, ,,,, in a SEALED, bottle I should be able to measure it for years, it will take more than a couple days in a sealed container.
On a practical basis I keep my solution of tap water, meta and acid for three months and if I am not opening the container for six months. Meta kills wine corks and some plastics and all metals (the spring in your hand sprayer) so these also get replaced.
In micro I was taught that cleaning with cold tap water removes most of the micro count, hot water removes about ten times more count and soaps remove about a hundred times more contamination.
,,,,,, if it looks clean most of the contamination is gone but if there are pores (wood barrels) or rubber gaskets chemical treatment adds a useful layer of safety


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## justsipn

@Rice_Guy , as always....thank you so much for your information. This makes me feel better. I always keep it in a sealed container. 

It also might explain why my spray bottle seems to be working less and less.


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## cmason1957

I was down in my wine area to do some racking last weekend, last time I was there was prior to knee replacement surgery first week of October. I opened the jug I had mixed up then that was still more than 3/4 full, had been sealed since I was last there. Took a nose hit as soon as I pulled the stopper out, it was still perfectly good.


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## hounddawg

bstnh1 said:


> There is no need to rinse. According to Tim Vandergrift, after a couple of minutes the amount of sulfites is negligible. He has stated that he never rinses k-meta from anything. I have never rinsed anything.


nor have i, when using K-meta, for several years, and on my 3 basin sink i fill one basin with k-meta solution and keep my hydrometer, ferment stirrer, and airlock and bungs for at least a week, knock on wood,, with out problems, but just my routine,, 
Dawg


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## hounddawg

so adding citrus acid to a k-meta solution will add affectedness to a k-meta solution ? 
just wondering,
Dawg


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## Rice_Guy

pH 1.8 is where half of the meta is in the active SO2 form and half is in the inactive salt form, the ratio of active versus inactive improves the lower the pH.


hounddawg said:


> so adding citrus acid to a k-meta solution will add affectedness to a k-meta solution ?
> just wondering,


_while you are wondering/ reading up this balance point is called the pKa_


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## winemaker81

balatonwine said:


> I had to learn, there are no "obvious" points.


YUP! I'd rather be told one time too many than one time too few!



CDrew said:


> You guys realize this thread is from 2008! The info is still relevant though.


Some folks get upset over thread necromancy, but most technical discussions are just as valid today as they were at the time.


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## Johnd

hounddawg said:


> so adding citrus acid to a k-meta solution will add affectedness to a k-meta solution ?
> just wondering,
> Dawg


Yes, by using acid to decrease the pH (increase acidity) of the solution, the effectiveness of the sulfite solution is increased. Citric acid has traditionally been used to decrease the pH as it remains clear in solution, tartaric has a tendency to cloud after a while, making the solution a milky color. I don't know if it loses its effectiveness when it gets cloudy.


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## bstnh1

winemaker81 said:


> YUP! I'd rather be told one time too many than one time too few!
> 
> 
> Some folks get upset over thread necromancy, but most technical discussions are just as valid today as they were at the time.


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