Potassium Metabisulfite Question

[hounddawg]

Did you add Kmeta during those two years.

no just the first and only rack, I S-air lock and keep them full, then i rack to clean carboy with K-meta and sorbate then bottle
Dawg

 

[Cap Puncher]

Why? One thing that comes to mind is the evaporation through the wood, but I can't see that affecting SO2, although that's a guess and not personal knowledge.

The microoxygenation from the barrels is what causes the free SO2 to decrease more in barrels. This happens more if you have low humidity dry conditions which causes more evaporation “Angel’s Share”.
I see this happen in my 15 gallon barrel and I lose 10-15 free ppm every 1-2 months. This matters a lot more for high pH wine.

 

[winemaker81]

I see this happen in my 15 gallon barrel and I lose 10-15 free ppm every 1-2 months.

Thanks for the info!

 

[Rice_Guy]

Did you add Kmeta during those two years.

The “rules” for newbies or is it kit makers say every three months.

My pattern is add K meta every time I open a carboy, therefore if I have pulled gross lees at four weeks or so and don’t have a lot of lees (added clarifier) a carboy will get racked and metabisulphite / bottled next March when I am selecting contest wines. The most extreme example of sulphite every time it is opened was a carboy of black raspberry in mom’s basement which had a solid cap put on it in 1978, in 2001 when I was taking over mom’s equipment that carboy was still in good shape. , , , , next my pattern is to assume that free SO2 is zero every addition therefore dose the maximum meta each time a carboy is opened.

I don’t run oak barrels so I don’t have data/ decay numbers on consumption of free SO2. My assumption from the ”rule” that one should top off a barrel (to minimize oxidation) is that the barrel ullage is an oxygen environment and a adding meta every time it is topped off would be wise.

 

[winemaker81]

I don’t run oak barrels so I don’t have data/ decay numbers on consumption of free SO2. My assumption from the ”rule” that one should top off a barrel (to minimize oxidation) is that the barrel ullage is an oxygen environment and a adding meta every time it is topped off would be wise.

I top the barrels every 3 to 4 weeks, so a full 1/4 tsp per 5/6 gallons would be too much. Mine are 54 liter / 14.25 US gallons, so I've been adding 3/4 tsp every 3 months. Given that 3 months is 13 weeks, if I add 1/4 tsp at each topup, that gives me 3 to 4 doses, e.g., 3/4 tsp to 1 tsp.

This requires more thought, but on the surface it's adding up.

 

[cowine7]

I have a QUESTION:

If i have 50 mg/ l So2 (ppm), how can i calculate to add as Potassium metabisulfite ?
(because is solid, need in grams i think...)

 

[Raptor99]

I have a QUESTION:

If i have 50 mg/ l So2 (ppm), how can i calculate to add as Potassium metabisulfite ?
(because is solid, need in grams i think...)

Kmeta powder is 57% SO2 by weight, so to get 50 mg/L you need:
50 / 0.57 = 87.7 mg/L of Kmeta powder

If your carboys are measured in U.S. gallons, then for each gallon you need:
87.7 mg/L * 3.7854 L/Gal = 331.98 mg of Kmeta powder (or 0.332 g)

You will need a small scale accurate to 0.01 g.

If you measure the pH, you can fine-tune the amount of Kmeta to add. 50 mg/L of free SO2 is for 3.6 pH. If the pH is lower you need less. pH 3.3 only needs 26 mg/L free SO2. More info on that here: https://www.accuvin.com/wp-content/uploads/2015/04/How-SO2-and-pH-are-Linked.pdf

 

[She’sgonnakillme]

I top the barrels every 3 to 4 weeks, so a full 1/4 tsp per 5/6 gallons would be too much. Mine are 54 liter / 14.25 US gallons, so I've been adding 3/4 tsp every 3 months. Given that 3 months is 13 weeks, if I add 1/4 tsp at each topup, that gives me 3 to 4 doses, e.g., 3/4 tsp to 1 tsp.

This requires more thought, but on the surface it's adding up.

@winemaker81 I am just now starting my two new rbarrel break-in’s (both 20L) and really don’t want to fuss with PH / So2 testing unless I really need to. Using your method/approach, what would you suggest as far as how often I should top off and also how much K Meta should be added each time I do top off? Thanks for the help.

 

[Rice_Guy]

The generic answer is top up at a couple inches/ less than two.
There are several factors on when on the calendar. It is worth while filling to see how fast your condition is. , , , You can control some of this, for example
* Warm temperature will evaporate faster.
* High humidity as a cave will reduce the rate.
* air pressure as Denver is faster than the coast
* quality of wood

am just now starting my two new barrel break-in’s (both 20L) and really don’t want to fuss with PH / So2 testing unless I really need to. Using your method/approach, what would you suggest as far as how often I should top off

 

[Sailor323]

Back when I made large quantities of wine from grapes, I typically racked when primary fermentation was complete and added 1/4t per 5 gallons at that time. Then during the clarification stage I would rack every 2 or 3 months and added 1/4 tsp at each racking and finally 1/4t at bottling. While I still follow that regimen for kit wines that spend a lot of time in carboys post fermentation I also make a few wines for quick drinking--racking after fermentation at which time I add meta, then additional racking at 2 week intervals 2 or 3 times and typically bottling at 8 weeks after beginning the process. How necessary is it to add meta at each racking? Does the dose of meta added post fermentation persist in the wine? for how long? Does it really matter since SO2 allergy is not a problem for me?

 

[winemaker81]

I am just now starting my two new rbarrel break-in’s (both 20L) and really don’t want to fuss with PH / So2 testing unless I really need to. Using your method/approach, what would you suggest as far as how often I should top off and also how much K Meta should be added each time I do top off?

As @Rice_Guy said, many things affect the evaporation rate of a barrel, so I can't provide concrete answers. You'll have to experiment to see what your barrels' requirements are. But I can tell you what I do, to use as initial guidelines.

My barrels are 54 liter, triple the size of yours, and both are well into neutral (manufactured in 2010). I add oak cubes to provide the flavoring while the barrels provide the concentration effect.

The former owner said the barrels average about 500 ml top up per month, and this appears accurate, but it varies. I top up every 3 to 5 weeks, 3 in the summer, 4 to 5 in the fall and spring, and 3 to 4 in the winter. In the summer my cellar heats up (70-75 F) and the winter it's 58-60 F. Summer and winter the humidity is the lowest. This explains my apparently odd variation in top up times.

In the summer I'll add 750 ml at top up, and less than 500 ml during cooler times in the spring and fall. I figure the angel's share of each is about 10% over a year's time. I plan 16 US gallons of wine to keep each barrel full.

I've been adding 3/4 tsp K-meta to each barrel (54 liters, 14.25 US gallons) every 3 months. However, based upon recent conversations I'm considering use 1/4 tsp per barrel at each top up. This works out to a bit more than 3/4 tsp every months, but as @Sailor323 said, SO2 is not an issue for me, and the overall additions during a year are well below the industry maximum level.

If I had new 20 liter barrels?

I'd put the heaviest reds in the barrels first and leave them 4 weeks. At that time, gently stir the barrels to ensure the wine is mixed, and taste. It's highly likely the wines will have absorbed enough oak to swap them out. If not, let them go another 2 to 4 weeks.

I draw a sample at each topup, although with my barrels it's not a necessity, just a pleasure. I love seeing how the wine develops over that first year.

Note that you have small barrels, so the volume to internal surface area ratio is lower, so 4 weeks may be too much. I'm making a wild-assed guess on that. However, if a wine gets over-oaked, either blend unoaked wine into it OR use it to top up other wines. With the amount you're making, a batch or two that is overoaked is NOT a real problem.

From what I gather, each succeeding batch can remain in the barrel twice the time of its predecessor, roughly 4, 8, 16, 32 weeks. Note that this depends on the wine, e.g., a lighter red will be overpowered by the oak sooner than a heavier one. This is simply a rough gauge -- you'll have to monitor the barrels for the first one to two years. After that the oak character is diminished enough that you may have to start adding oak adjuncts.

Also note that you'll get little evaporation effect during the first few batches, as the wines won't be in there long enough.

You asked for help ... I wrote Phd thesis!

 

[She’sgonnakillme]

As @Rice_Guy said, many things affect the evaporation rate of a barrel, so I can't provide concrete answers. You'll have to experiment to see what your barrels' requirements are. But I can tell you what I do, to use as initial guidelines.

My barrels are 54 liter, triple the size of yours, and both are well into neutral (manufactured in 2010). I add oak cubes to provide the flavoring while the barrels provide the concentration effect.

The former owner said the barrels average about 500 ml top up per month, and this appears accurate, but it varies. I top up every 3 to 5 weeks, 3 in the summer, 4 to 5 in the fall and spring, and 3 to 4 in the winter. In the summer my cellar heats up (70-75 F) and the winter it's 58-60 F. Summer and winter the humidity is the lowest. This explains my apparently odd variation in top up times.

In the summer I'll add 750 ml at top up, and less than 500 ml during cooler times in the spring and fall. I figure the angel's share of each is about 10% over a year's time. I plan 16 US gallons of wine to keep each barrel full.

I've been adding 3/4 tsp K-meta to each barrel (54 liters, 14.25 US gallons) every 3 months. However, based upon recent conversations I'm considering use 1/4 tsp per barrel at each top up. This works out to a bit more than 3/4 tsp every months, but as @Sailor323 said, SO2 is not an issue for me, and the overall additions during a year are well below the industry maximum level.

If I had new 20 liter barrels?

I'd put the heaviest reds in the barrels first and leave them 4 weeks. At that time, gently stir the barrels to ensure the wine is mixed, and taste. It's highly likely the wines will have absorbed enough oak to swap them out. If not, let them go another 2 to 4 weeks.

I draw a sample at each topup, although with my barrels it's not a necessity, just a pleasure. I love seeing how the wine develops over that first year.

Note that you have small barrels, so the volume to internal surface area ratio is lower, so 4 weeks may be too much. I'm making a wild-assed guess on that. However, if a wine gets over-oaked, either blend unoaked wine into it OR use it to top up other wines. With the amount you're making, a batch or two that is overoaked is NOT a real problem.

From what I gather, each succeeding batch can remain in the barrel twice the time of its predecessor, roughly 4, 8, 16, 32 weeks. Note that this depends on the wine, e.g., a lighter red will be overpowered by the oak sooner than a heavier one. This is simply a rough gauge -- you'll have to monitor the barrels for the first one to two years. After that the oak character is diminished enough that you may have to start adding oak adjuncts.

Also note that you'll get little evaporation effect during the first few batches, as the wines won't be in there long enough.

You asked for help ... I wrote Phd thesis!

@winemaker81..That’s great and thank you for taking the time to reply. I am going to stay with Cabs, Merlots and Supers only for the first year so oaking will be easier to gauge and as you said more forgiving. So if I follow the same formula I use for carboys of 1/4 tsp k meta per racking or at every 3 months even while in barrels it should still be good enough. I know some state that you lose it faster in barrels, but it also seems that people do not recommend leaving wine in these small 20L barrels any longer than 3 months anyway do to concerns of over micro oxidation, if that’s the case SO2 levels would be less of a concern I would think?! Am I wrong with these assumptions? BTW I love your website and blogs! Great readings and learnings to be had!!!!

 

[winemaker81]

I am going to stay with Cabs, Merlots and Supers only for the first year so oaking will be easier to gauge and as you said more forgiving.

It does make things simpler. As I remarked in a different post, I'm at the point where less than 15 gallons of a red is almost a waste of my time, as a carboy is gone too fast.

So if I follow the same formula I use for carboys of 1/4 tsp k meta per racking or at every 3 months even while in barrels it should still be good enough. I know some state that you lose it faster in barrels, but it also seems that people do not recommend leaving wine in these small 20L barrels any longer than 3 months anyway do to concerns of over micro oxidation, if that’s the case SO2 levels would be less of a concern I would think?! Am I wrong with these assumptions?

Some folks test pH and SO2 and carefully craft their sulfite levels. If anything, the "1/4 tsp per 5 gallons" is more than what people are stating as targets, so IMO it's fine. My 2019 wines that spent 11 months in the barrel are holding up just fine. However, I am leaning towards 1/4 tsp / 14.25 gallons at each topup to allow for extra SO2. IIRC, the details were provided by @Rice_Guy, and his presentation of facts is reliable.

Regarding evaporation rates, record how much topup you use each time. If your rate is similar to mine (10%/year) I don't see a problem with leaving the wine in the barrel longer for that reason. A new barrel will heavily oak the wine, which is different from the evaporation effect. Over-oaking is the primary reason to limit barrel time for new barrels.

In a discussion last summer (?), @Johnd and I exchanged notes regarding barrels and evaporation. I tried to develop a rough formula for evaporation rates by barrel size, but there are way too many uncontrollable variables, including barrel volume, internal surface area, wood porosity, humidity, temperature, probably the wine type, etc. My research was interesting, but provided no solid answer.

As I'm wont to say, we apply as much science as we can to winemaking, but in the end it's a natural process so winemaking is an art.

BTW I love your website and blogs! Great readings and learnings to be had!!!!

I'm happy it's useful! I started writing blogs on topics we discuss here, to record my thoughts and process on each subject, in detail. We answer variations on the same questions over and over, and it's better to write it once -- in detail -- than to piece-meal it out repeatedly.