Campden Tablets vs. Potassium Metabisulfite question.

[MJJ]

If a recipe calls for using a Campden Tablet a day before pitching the yeast & I don't have any. Can it be successfully & safely substituted with Potassium Metabisulfite ?

Thank You for your time.

[wayneb]

Yes, you can! A Campden tablet is simply potassium metabisulphite (or sodium meta, if you buy the older, cheaper kind) compressed into tablet form for ease of measure. You can always use 0.44g of metabisulphite powder in place of the most common size Campden tablet.

[MJJ]

Originally Posted by wayneb

Yes, you can! A Campden tablet is simply potassium metabisulphite (or sodium meta, if you buy the older, cheaper kind) compressed into tablet form for ease of measure. You can always use 0.44g of metabisulphite powder in place of the most common size Campden tablet.

Since I only speak newbee, 0.44g = what in measuring spoons?

[TAKeyser]

Originally Posted by MJJ

Since I only speak newbee, 0.44g = what in measuring spoons?

The directions on my Potassium Metabisulfite gives 1/4tsp per 5 gallons

[wayneb]

OK - one teaspoon (US dry measure) of potassium metabisulphite weighs approximately 1.4 grams. So, 0.44 grams (the contents of one Campden tablet) is 0.44/1.4 = 0.314, or roughly 1/3 of a teaspoon.

While working in teaspoon measure is certainly possible, you'll get much more precise results if you can weigh your materials, since the amount of settling in a teaspoon of any dry crystalline powder can vary the weight by 10% or more. You can get a relatively cheap (under $25) gram scale from places like eBay, and they are far more accurate than working in teaspoons.

[MJJ]

Originally Posted by wayneb

OK - one teaspoon (US dry measure) of potassium metabisulphite weighs approximately 1.4 grams. So, 0.44 grams (the contents of one Campden tablet) is 0.44/1.4 = 0.314, or roughly 1/3 of a teaspoon.

While working in teaspoon measure is certainly possible, you'll get much more precise results if you can weigh your materials, since the amount of settling in a teaspoon of any dry crystalline powder can vary the weight by 10% or more. You can get a relatively cheap (under $25) gram scale from places like eBay, and they are far more accurate than working in teaspoons.

Thank You for the advice, It is very much appreciated.

[TAKeyser]

Originally Posted by wayneb

OK - one teaspoon (US dry measure) of potassium metabisulphite weighs approximately 1.4 grams. So, 0.44 grams (the contents of one Campden tablet) is 0.44/1.4 = 0.314, or roughly 1/3 of a teaspoon.

While working in teaspoon measure is certainly possible, you'll get much more precise results if you can weigh your materials, since the amount of settling in a teaspoon of any dry crystalline powder can vary the weight by 10% or more. You can get a relatively cheap (under $25) gram scale from places like eBay, and they are far more accurate than working in teaspoons.

OK the directions on my Campden Tablets says 1 tablet per gallon, so if I'm reading your math correctly that is the equivalent of 1 2/3 teaspoons of Pottassium Meta Bisulfilte for a 5 gallon batch. My package of Potassium Meta Bisulfite says 1/4 tsp for a 5 gallon batch and that seems to be a really big discrepancy?

[wayneb]

Yeah - but the various "rules of thumb" on the use of metabisulphite are hugely different as they are all based on different assumptions, and the actual level of molecular and free SO2 that an addition of metabisulphite produces can vary all over the place, based on the pH of the liquid and the amount of SO2 binding chemicals present in the must. There are several great discussions on sulphite additions in past threads here on Gotmead (some of them are in the Patron's sections), so drill down using the search tool, and become enlightened!

BTW - that one tablet per gallon instruction on your tablets, IMO, adds enough free SO2 to kill a horse in most musts (figuratively speaking). There have been several different sizes of Campden tablets produced over the years since I started brewing - do you happen to know the effective mass (weight in grams) for yours?

[TAKeyser]

Don't know the effective weight, I know from the company that each tablet adds 75 ppm free SO2 per gallon. They are LD Carlson brand and just looking at the package it actually says use 1 to 2 Tablets per Gallon, though I've always just added 1.

[MJJ]

Originally Posted by wayneb

Yeah - but the various "rules of thumb" on the use of metabisulphite are hugely different as they are all based on different assumptions, and the actual level of molecular and free SO2 that an addition of metabisulphite produces can vary all over the place, based on the pH of the liquid and the amount of SO2 binding chemicals present in the must. There are several great discussions on sulphite additions in past threads here on Gotmead (some of them are in the Patron's sections), so drill down using the search tool, and become enlightened!

BTW - that one tablet per gallon instruction on your tablets, IMO, adds enough free SO2 to kill a horse in most musts (figuratively speaking). There have been several different sizes of Campden tablets produced over the years since I started brewing - do you happen to know the effective mass (weight in grams) for yours?

each tablet equals 1/16 tsp of sodium bisulfite.

75 ppm of sulfur dioxide (so2) per gallon


Dont ask me to translate, Its all greek to me. Except for "1/16 tsp"




the potassium metabisulfite says
usage 1/8 tsp per gallon = approx 100 ppm of free so2

[wayneb]

ARRGH! Well part of the discrepancy is my memory. I incorrectly recalled the 1.4 gram to tsp relationship, but in fact now that I check my reference sources, 1.4 g of metabisulphite is what 1/4 tsp weighs.

Sorry about that!

Re-doing the calculation, and realizing that 1.4 g per 1/4 tsp translates to 5.6 g per tsp, 5.6 g/tsp / .44 g/tablet means one tsp of metabisulphite powder is roughly equivalent to 12-1/2 tablets (that's for potassium meta, the equivalence for sodium meta is slightly different). That reduces the discrepancy a bit. All these conversions, and my inability to do arithmetic without resorting to a calculator, is one of the reasons why I prefer to work only in grams.

[MJJ]

the potassium metabisulfite says
usage 1/8 tsp per gallon = approx 100 ppm of free so2



I have a follow up question.
Is this "potassium metabisulfite" safe to use twice? For example, Before pitching yeast, I use it to kill any possible bugs in the must. When the must has finished sweet, Can I use it again to kill remaining yeast following with sorbate
a few hrs later?

[TAKeyser]

Originally Posted by MJJ

each tablet equals 1/16 tsp of sodium bisulfite.

75 ppm of sulfur dioxide (so2) per gallon


Dont ask me to translate, Its all greek to me. Except for "1/16 tsp"

It's all Greek to me as well i just follow the directions on the packaging, if it says 1/2 tsp that is what I use, if it says 2 grams I weigh it out and do it that way. Seems to work for me.

[wayneb]

Originally Posted by MJJ

the potassium metabisulfite says
usage 1/8 tsp per gallon = approx 100 ppm of free so2



I have a follow up question.
Is this "potassium metabisulfite" safe to use twice? For example, Before pitching yeast, I use it to kill any possible bugs in the must. When the must has finished sweet, Can I use it again to kill remaining yeast following with sorbate
a few hrs later?

It is safe to use, and up to doses in the neighborhood of 300 ppm it would be almost undetectable in the flavor or aroma profile by the vast majority of people. In fact since the amount of free SO2 decays over time (usually taking days to reduce to insignificant amounts), it is common practice to add sulphites several times during the production of commercial wines. So if you wanted to add another 1/8 tsp just before you add the sorbate, you certainly can.

Do keep in mind that several factors (including pH and any compounds that can "bind" the sulphite in your mead), can actually make the actual ppm concentration of free SO2 significantly less than that predicted by the dosage indicated on your meta package. So if I were you I would certainly add an additional 1/8 tsp before sorbate addition, and I might even add another dose prior to bottling if you age this one in bulk for any extended time before getting it into the bottle.

[MJJ]

Originally Posted by wayneb

It is safe to use, and up to doses in the neighborhood of 300 ppm it would be almost undetectable in the flavor or aroma profile by the vast majority of people. In fact since the amount of free SO2 decays over time (usually taking days to reduce to insignificant amounts), it is common practice to add sulphites several times during the production of commercial wines. So if you wanted to add another 1/8 tsp just before you add the sorbate, you certainly can.

Do keep in mind that several factors (including pH and any compounds that can "bind" the sulphite in your mead), can actually make the actual ppm concentration of free SO2 significantly less than that predicted by the dosage indicated on your meta package. So if I were you I would certainly add an additional 1/8 tsp before sorbate addition, and I might even add another dose prior to bottling if you age this one in bulk for any extended time before getting it into the bottle.

That is very good to know, Thank You.

[hepcat]

Excellent question mjj, I've been wondering the same thing, I knew that campden tabs are pot meta but had decided that it would just be easier to use the tabs as they supposedly contain the correct amount of it so you don't have to worry about measuring/weighing such tiny amounts(if you want to add to less than a 5 gallon batch for example). I already have the powder and wanted to get some tabs on the last visit to my local LHBS but a new shipment had just arrived and were still buried under alot of other inventory they had not yet had a chance to unpack yet, I think I will get them next visit.