How much free SO2 is lost after filtering?

[Juggernaut]

I want to add Potassium Metabisulphite to my red wine now because my free SO2 test titrets expire this month. I'm planning on filtering and bottling next month. I'm wondering how much free SO2 I can expect to lose after I've filtered so I can calculate that in.

Also I'm using this for the calculations. http://www.extension.iastate.edu/NR...96C04C8DC4A/163603/SulfurDioxideAdditions.pdf
Does this account for SO2 that is getting bound up?

 

[sour_grapes]

For your second question, I would say that this worksheet does NOT take into account SO2 getting bound. The worksheet says that K-meta is "57% SO2." The molar mass of SO2 is 64 g/mol, and there are two of them per K-meta molecule. The molar mass of K-meta (K2S2O5) is 222 g/mol. (2*64g/mol)/(222g/mol)=0.57. So it appears that this worksheet is assuming all the SO2 derived from the K-meta that you add will go to free SO2.

 

[ibglowin]

I have tested SO2 (free) both before and after vacuum filtering. I see an INCREASE in free SO2 after filtering. This is due to the fact that I run KMETA through the filter and lines in order to sanitize. There is enough KMETA in the filter (after draining all the lines) that I have seen anywhere from 7-12 ppm increase in free SO2. It depends on how long you let the filter drain out.

 

[Juggernaut]

Thanks for the replies. After reading them I think I better filter now, check the SO2 level, and then I can bottle at a later date. My only question mark is how much extra KMETA do I add to compassionate for the SO2 that will be bound?

 

[ibglowin]

There is no way to know without accurate testing using either an A/O Rig or Vinemtrica.

 

[Juggernaut]

What do you suggest I do then?

 

[ibglowin]

How much KMETA has been added already?
Is this a kit or what exactly you don't really say?
How long has it been since you added your initial dose of KMETA?
Do you know at least an accurate pH?

 

[sour_grapes]

Wait, Juggernaut says he is going to test the SO2 levels, ergo, he has a way to test them. I would filter, test, and then add the amount (say, from that worksheet) that should bring the free SO2 up to the right level (assuming no more is bound). Then test again, and add more if needed. (This seems too simple; did I miss something that makes this uncertain?)

 

[Juggernaut]

I was hoping I could test once and make an adjustment to my calculation to compensate for the SO2 that will be bound after adding the Kmeta. I don't have enough test titrets for two tests and these things expire faster then I use them. Sorry I didn't want to make this complicated. I have 3 Chilean wines going from juice buckets. A Cabernet sauvignon, a Carmenere, and a Malbec.They were started in April and racked three times with an initial does of a 1/4 teaspoon of KMETA on the first racking. I tested the Carmenere in October and it had a free SO2 of about 18 and a PH of about 3.3 (PH Strip).

 

[ibglowin]

The amount of KMETA required to protect your wine is based solely on the wines pH. Its that simple. The lower the pH the less SO2 is required to protect it and vice versa. Knowing the pH is step one. You don't know the pH you can't really go on to step two. pH strips are not very accurate either. My best (guess) advice for you is that since you have only added an initial dose (1/4 tsp which seems low) back in April and nothing since then and its now 8 months later that you add another 1/4 tsp and call it good.

If you plan on staying with the hobby you should invest in some testing equipment (pH meter and either Vinemetrica or A/O rig for SO2) The pH meter can also be used for testing TA.