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Help Problem with smell of sulphur dioxide

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A Stephenson

Registered Member
Feb 11, 2013
UK, South West

I started getting the smell of sulfur dioxide coming out of the airlock.
PH 3.6

I added 7g calcium carbonate in 1 L of water with 4 tsp of yeast nutrient & energiser, stirred and waited for 2 hours.

Smell has decreased and a sweeter smell coming back, fermentation rate has increased and is vigorous.
PH test 3.8 so added another 7g of calcium carbonate and degassed must after pitching.

I expect the PH to be 4.0 and intend to keep it there for a while to prevent the yeast getting unhappy. Lalvin 71B seem to like PH above 3.8?

Must temperature has gone up from 22.5c to 24.5c.

Below is my full recipe. I did not have potassium carbonate, will have to buy some, but have calcium carbonate.
The pollen and yeast nutrient & energiser should be sufficient.


Sweet Sack Traditional Mead

Abv % 14.5 - 15
Volume 25 Liters
OG 1135
FG 1025

Fermentation PH 3.9 - 4.0 minimum

Clover honey 11.80 Kg
Water 16.43L (10L chilled)
10g Lalvin 71B
Yeast Nutrient & Energiser @ 25L (3tsp/4.5L) 16.5 tsp. Will only use 8 tsp.
Pollen 30g/L @ 25L = 750g

Boiled 2L water pitched into 35L fermentation bucket.
Dissolved 4 tsp yeast nutrient & energiser in water.
Added honey 26 x 454g jars
Mixed and aerated.
Added 16.43L water using chilled to obtain temperature of 22c

Checked SG which is estimated at 1.150, as my hydrometer's scale only goes to 1.120 with approximate scale to 1.130.

Added 2 liters of water making up 27 L
OG approx 1.132
PH 6.5
Temp 22.5c

Re-hydrated 10g Lalvin 71B as instructed on package and pitched at 15 mins.
Yeast foamy stirred to suspend and temperature was 36c and dropping.

Pitched in the centre of must and left for 2 hours.

Added 800g of pollen which was an adjustment for 27L, short 10g.
Must temperature 22c

Fermentation occurred after 12 hours, but within 16 hours.

Aerated must 3 times over the course of the day stirring the pollen to make sure all is dissolved.

Added 5 tsp yeast nutrient & energiser.
PH checked at 4.5

SG checked approx 1.134.

Yeast nutrient & energiser for 29 L of must 19 tsp / 4 stages = 4.75 tsp
(will only be using half of required nutrients & energiser as pollen should provide rest)

Added 4 tsp before pitching yeast
Added 5 tsp 24 hours after pitching yeast.

I hope the Lalvin 71B yeast will achieve at least 14%, corresponding to a SG drop of .103 during ferment.

Medsen Fey

Fuselier since 2007
Premium Patron
I'm not sure why you are trying to keep the pH so high. 71B doesn't need the pH to be above 3.8; works fine even as low as 3.4. Because meads generally have relatively little TA compared to wines, they are more dependent on low pH to keep them from tasting flabby. While I am a big proponent of adjusting the pH with carbonates, I suggest raising the pH ONLY ENOUGH TO GET COMPLETE FERMENTATION. Usually somewhere in the 3.2 to 3.4 range is fine.

It would seem that with 30 g/L pollen added to 1/2 dose nutrients, your must should have enough nitrogen and micronutrients particularly for 71B. You might give it a dose of yeast hulls which can bind sulfur compounds and give it a good aeration to blow off as much H2S as possible.

My suspicion is that your fermentation temperature is too high at 24.5° C. A lot of yeast get stinky at that temperature.

A Stephenson

Registered Member
Feb 11, 2013
UK, South West
Thanks for the feedback, got a little worried. Have been stirring lots and aerating.

I though that PH should be between 3.7 and 4.6, but as 71B was good for range between 15 - 30c temp did not come to mind. Never had a problem with stinky fermentation like that, but it does not taste bad and it just crept in.

Will have to sink some sterile ice packs into must to keep temperature lower. Wanted to maintain max 22c.

Many thanks.

A Stephenson

Registered Member
Feb 11, 2013
UK, South West
Hi Medsen Fey,

Thanks for your help today, you were right the 71B seems to be quite pungent, compared to ale yeast, Lalvin D47 and EC-1118.

I freaked out a little when the sulphur type smell intensified. Ken's book advises optimum PH 3.7 - 4.6 so I was worried when it had dropped from 6.5 to 3.6 thinking that the yeast were becoming stressed and producing the pungent aroma.
It must have just been the esters that 71B produces that gave me the impression of a sulphur type smell.

The fermentation bucket is now in a water bath and temperature now down to 20c. Vigorous fermentation going on though.
Tasted a small sample of must and I think the 71B puts a unique musty floral type character in to the wine,, which seems to be the one I have been looking to achieve.

Many thanks.
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