Metallic residue in FV?

[ssashton]

Hi all,

Many times after fermenting a beer in my pressure barrel I find a silver metallic residue on the bottom of the (brass?) pressure valve in the middle of the lid.

I don't believe this is a problem; presumably just a result of condensation forming there because the metal is cool, combined with the various off-gassing compounds from the beer. Although, I'm not sure if it is only present on the pressure valve or also on those stainless screws (plugging unused holes) and the aluminium schrader valve for pressure monitoring. Since those are bright in colour it might be there but not noticeable, or not there at all which would suggest a reaction with the brass.

I'm curious if anyone knows exactly what is causing this, any ideas?

 

[foxy]

Could it be electrolysis, different metals over each other. Brass is not a good idea in a fermenting vessel, nor copper. While copper may be fine in a mash tun it isn't in a fermenter.

 

[ssashton]

The valve is not touching other metals, only the plastic lid.

I wondered if it's some kind of compound from the yeast, like sulphur. Only I think sulphur would look yellow.

 

[foxy]

The valve is not touching other metals, only the plastic lid.

I wondered if it's some kind of compound from the yeast, like sulphur. Only I think sulphur would look yellow.

In that case I would say the co2 in the fermenter, the co2 is not pure and the gas carries sulphur, water acid alcohol. As I said previously brass isn't good in a fermenting vessel. Can't you switch it for stainless?