Top fermentation - lumps

[Riastradh]

I have a few basic questions I need cleared up about fermenting ale. Are you alloud to let air at your beer in primary fermentation? Like, I know you can open the tub to take a gravity reading but does exposing it too much kill the yeast or anything?

On the surface of the beer, it's very lumpy - I assume those are little clumps of yeast hence top fermenting? I'm just worried it might be bad bacteria, how can you tell?

Do those lumps completely dissapear when fermentation has completed and can I stirr the lumps in and scrape down the spume left on the sides?

Oh yea...one more question *rolls eyes* ... this the temperature changes now and then, from about 16 - 24 C surely that won't ruin anything, it'll just slow it down when the temperature decreases then speed up again when the temp rises?

Thanks so much!

 

[SpanishCastleAle]

Allowing air in after fermentation has really got going can produce off flavors. It doesn't hurt the yeast, they rather like it but they also like fermenting at 90* F too.

It's prob yeast. Some strains do that more than others. In extreme cases the yeast can make too thick of a cake on top and the yeast is all stuck in that cake and not fermenting, leading to under attenuation. You can gently rouse/swirl it to get that yeast to fall back in.

During the early phases of fermentation you'd like to keep the temp cool (say mid 60's F on average). After the majority of fermentation you can let it warm up to room temp with no ill taste effects and better attenuation. But if you let it cool too much during the end of fermentation the yeast can floc out too quickly (causing under-attenuation). The yeast generates heat during the fermentation and that heat generation fades towards the end, so the beer usually will cool down a little at the end of fermentation (if the ambient temp is kept constant). Even more reason to make sure it doesn't get too cool towards the end.

 

[suprchunk]

Allowing air in after fermentation has really got going can produce off flavors.

Plenty of breweries still brew with open fermenters with no ill effects.

 

[ChshreCat]

As to the lumpy beer, if you mean you're seeing little things that look like someone flicked bits of cottage cheese in your beer, those are yeast colonies and are completely normal. If you mean the who top looks like lumpy beer meringue pie, that's krausen and is completely normal too. No stirring needed, and in fact you want to avoid agitating the beer if it's fermenting normally so things can settle out completely. don't worry about the floaties or the crusties on the side. When you siphon out of the primary to bottle or go to secondary, that'll get left behind. Just keep an eye on it and avoid anything floating as you get to the end of the siphon. If a little bit gets through, it's not the end of the the world though. It'll settle out again in secondary or in the bottle.

 

[Riastradh]

Thanks everyone, that's a brilliant help!