Infection?

[HT Shen]

Hi All,

My Friend helped me to do the dry hop process yesterday.
When he opened the fermentation tank, he found there is black color item on the tank (Point by Red color arrows).

He asked me what is it. My friends did taste the beer, and he said it looks like normal, but he is not quite sure.
I have no idea what is it, and this is the first time which I saw this after complete the fermentation processes.

Does anyone know what is it?
Does it infected?


Thanks
HT

 

[jschein]

Not infected, it looks like you didn’t scrub off all the machine oil before use. Don’t ask how I know

 

[bruce_the_loon]

Nope that is not an infection. Stainless steel tanks sometimes get that blackening at the upper edge of the krausen as some reaction between the drying yeast and the metal. I've had it a couple of times, even after proper cleaning so it isn't machine oil residue, and the beers have been fine.