Vinmetrica SC 100-A

[Kraffty]

My new SO2 testing kit arrived last Friday. List price everywhere is $299.00 but Midwestsupplies.com sent a 20% off promo code to me to entice an order since I hadn’t bought anything from them in about 3 years. Perfect timing since I was going to buy it this month anyway, It worked and at $239.00 I jumped on it.

I confess to reading the instructions a obsessive number of times and even watching youtube instruction videos before running my first tests but It really was pretty easy to use. The specific reason for buying this was in response to judges notes on a wine I entered in the Cellar Masters contest suggesting Mercaptans or maybe slight Oxidation as a flaw. Until now I’ve relied on throwing in 1 campden tablet per gallon whenever I rack with no clue where I really stood. My first test on my 2016 Cab showed 27ppm SO2 but at 3.79 ph it should have been at about 80ppm. I adjusted the ph down to 3.65 and plan to retest, rack and adjust the SO2 levels next weekend. My Pinot tested at 40ppm and at 3.5 ph was just where it was supposed to be.

Now for the hard part, by next weekend I just need to become a MIT level Chemist in order to understand to formulas for calculating the amount of K-meta and how to make the correct ratio solutions to add to the wines. Seriously though, the MoreWine Guide to Red Wine Making spells out the process in detail. At least I won’t be adding chemicals blindly from now on and that has to help make better and more consistent wines.

Mike

 

[Boatboy24]

Mike,

Congrats on a great purchase. I'd been going along much the same way you've been and was blissfully ignorant for quite a while. When I started having some 'sour' tasting wines, and later some difficulty getting some to complete MLF, I broke down and got one as well. I was shocked when I measured my first wine and found it was down at 17ppm!! That won't happen again.

I also read the directions several times and watched many a YouTube video before actually opening mine and using it.

 

[NorCal]

Here is the formula I derived:

Gallons of wine being treated X PPM wanting to add / 156.25 = grams of SO2

an example:

5 gallons of wine x 50 ppm wanting to add / 156.25 = 1.6 grams (which is a 1/4 teaspoon)

 

[Boatboy24]

@NorCal: does that account for part of the addition being bound up? That's the part I struggle with. Need to read more. I think that's in the MoreWine manual.

 

[Kraffty]

This is from Red Wine booklet, this is where I started thinking I needed to become a chemist.

PPM of “free” SO2 needed x 3.785 x Gallons (US) of wine you are adjusting
____OVER____
0.57 (the actual % of SO2 that will become “free” in your addition)

 

[sour_grapes]

This is from Red Wine booklet, this is where I started thinking I needed to become a chemist.

PPM of “free” SO2 needed x 3.785 x Gallons (US) of wine you are adjusting
____OVER____
0.57 (the actual % of SO2 that will become “free” in your addition)

A couple of comments, Kraffty, if I may.

I found that equation you reproduced very annoying, because it did not tell you WHAT UNITS the result was supposed to be in. So I just looked at the Morewine! Red Wine book. You reproduced it perfectly, so it wasn't your fault! By context, evidently, the quantity you will compute in that equation is in grams.

Secondly, they don't actually mean ppm. They want you to take your ppm value and divide by 1000, i.e., they really meant parts per thousand (ppt). Sheesh.

Third: your equation and NorCals are the same, once you multiply them out. I like NorCal's version better! I'd just use his.

 

[Tnuscan]

https://vinmetrica.com/sulfite-adjustments-what-to-do-with-my-so2-results/

http://srjcstaff.santarosa.edu/~jhenderson/SO2.pdf


https://www.practicalwinery.com/janfeb09/page5.htm

 

[Kraffty]

Thanks Paul, I freely admit to being confused by that formula. Norcal's seems so much simpler but the one I copied is supposed to adjust for bound SO2 so, as Boatboy asked, does the @Norcal formula account for that?
Mike

 

[BigSell]

http://winemakermag.com/1301-sulfite-calculator

Try this, takes all the guess work out of it.

 

[sour_grapes]

Thanks Paul, I freely admit to being confused by that formula. Norcal's seems so much simpler but the one I copied is supposed to adjust for bound SO2 so, as Boatboy asked, does the @Norcal formula account for that?
Mike

I understand why you said that, but I do not believe the formula you cited accounts for bound SO2. I am guessing you made that statement because your formula computes "the amount of SO2 that becomes free." But the opposite of "free" is not "bound" in this case. I am pretty sure they don't mean that the rest of it is "bound." Instead, that factor of 0.57 is to account for the portion of the k-meta that is not SO2, namely, the potassium part (and a little O).

As I say, your formula and NorCal's formula are the same formula. Whatever one does, the other will do.

I think one working assumption is that after your first SO2 addition, all the SO2 that will become bound does become bound. Thus, you have already "paid the toll" with your first addition; your first addition will NOT provide as much free SO2 as the formula predicts, but later additions WILL. Perhaps Greg or Mike or an experienced winemaker can check that statement.

 

[ibglowin]

Paul is correct (as usual!) ~57% of a pure KMETA powder is the SO2 that is available to protect your wine. The other part is the useless (for the most part) potassium molecules.

 

[sour_grapes]

Paul is correct (as usual!) ~57% of a pure KMETA powder is the SO2 that is available to protect your wine. The other part is the useless (for the most part) potassium molecules.

Actually, the part I was looking for correction or confirmation on was this last paragraph:

I think one working assumption is that after your first SO2 addition, all the SO2 that will become bound does become bound. Thus, you have already "paid the toll" with your first addition; your first addition will NOT provide as much free SO2 as the formula predicts, but later additions WILL. Perhaps Greg or Mike or an experienced winemaker can check that statement.

Said another way: Is it true that some of the first k-meta dose will be bound to various sulfite sinks, but then, once these binding sites are saturated, all the SO2 that later k-meta doses provide will be free?

 

[Boatboy24]

I always thought (which is dangerous), that part of each dose would be bound. Don't ask me where I got that idea - there's all kinds of crazy stuff floating in this brain and I've no idea where it originated.

 

[Johnd]

Part of every dose will be bound, but not an initial big chunk like the first dose, and it becomes bound over time as the sulfite reacts. That is my understanding.

 

[dcbrown73]

FermCalc is your friend.

 

[ibglowin]

I believe so and that is why Kits come with 4-5gms of KMETA. Way overkill and about 2X more than you need if you use the wine`maker mag sulfite calculator but then the extra is just for initial purpose, tie up everything you can with SO2 and yet still leave plenty (free) to protect the wine until it gets bottled down the road in 3 months or so.

Actually, the part I was looking for correction or confirmation on was this last paragraph:



Said another way: Is it true that some of the first k-meta dose will be bound to various sulfite sinks, but then, once these binding sites are saturated, all the SO2 that later k-meta doses provide will be free?

 

[Boatboy24]

FermCalc is your friend.

What is the "SO2 Equilibrium Constant"?

 

[ibglowin]

Chapter 4 : Chemical Equilibrium

What is the "SO2 Equilibrium Constant"?

 

[dcbrown73]

What is the "SO2 Equilibrium Constant"?

It's chemistry hocus pocus.

I generally do not assess that when I'm working with FermCalc. I just tally how many grams of SO² to add to my batch.

Based on what I can tell, (ie, Googled) it's the concentrations required to create an equilibrium between NO² and SO² to produce SO³ (and the equilibrium to eliminate the other two chemicals?)

This is beyond my current understand why you want the equilibrium to create SO³. You want SO², so why would you want it all converted to SO³?

Maybe someone else that actually understands it can explain it because I have no idea!

 

[sour_grapes]

What is the "SO2 Equilibrium Constant"?

If I may paraphrase Jim's question, perhaps he is pointing out that if you have to guess a number, then this calculator is not that helpful. (Not sure if that is a valid interpretation, Jim.)

However, the situation is not as bad as that. The equilibrium constant (and the pH, for that matter), only come into play if you are trying to determine the level of molecular SO2. For free SO2, it does not matter what number you put there. Moreover, FermCalc only allows a narrow range of equilibrium constants, so it doesn't matter too much anyway whether you have a way of knowing the precise value.