Camden tablets' effect on yeast

[alan.monaghan]

I'm a bit worried about adding camden tablets/sodium metabisulphate to sanitise the water. Won't this kill off the yeast during fermentation, or does the chemical reaction remove the harmul ingredient (sulphite?). If so is there an upper limit to the amount which should be added?

[steve_flack]

Although yeast is affected by sulphite, the concentration required is considerably above what you'd get from using campden tablets to treat for chlorine - you shouldn't really be trying to sanitise water with bisulphite. Bisulphite is a rubbish sanitiser.

[alan.monaghan]

Thanks. Just found an old Boots campden tablet packet from earlier brewing days, which recommends usage a minimum of 24 hours before fermentation, so I presume its effects wear off with time (and possibly with boiling?). The main ingredient is sodium metabisulphate though!

[Jim]

I'm assuming that your intention is actually to sanitise the water?

Many brewers add 1/2 campden tablet to each 5 gall of tap water, but that's to neutralise the chlorine, not to sanitise it.

[alan.monaghan]

My mistake. My concern was about adding camden tablets to the water, ie water treatment, rather than sanitising. I have previously relied on boiling to remove chlorines but thought I might need to add campden tablets to remove chloramines. Since I use camden tablets/sodium metabisulphate to sanitise the equipment I was concerned that its effect on the baddies might carry over to the goodies if I added it to the water. It looks like thats not a problem if the water is left to stand (presumably in a sealed container) for 24 hours before use.

[sib67]

It looks like thats not a problem if the water is left to stand (presumably in a sealed container) for 24 hours before use.

There's no need to let the water stand for 24 hours after treating with Campden tablet(s).

[FlippinMental]

I've taken to filling the hlt and leave to stand overnight with the lid loose fitted. this method provides the opportunity to set timers to automatically heat the water while I'm still tucked up in bed

[alan.monaghan]

Thanks for all the useful comments. To remove both chlorines and chloramines I've added sodium metabisulphite to the water at the same rate as the suggested amount (by volume) for camden tablets (as these are 93% SM). I'm not sure if this is any less effective than adding it in solution. I have left it overnight, but not to have any effect on water treatment but purely because of the note on the old Boots camden tablet packet which recommends leaving 24 hours between use and fermentation - not sure why they recommend this but I'm assuming its effect as a sanitiser will have worn off by then, and the yeast will be safe (if it was ever under any threat from such a small dose).