1.070 OG, is one pack US-05 enough?

I usually pitch directly into the wort, just like Fermentis suggests . And I, too, use US-05 almost exclusively.

 

@mikehartigan is indeed correct that on the US-05 package is simply provides instructions to just “sprinkle into wort”. That is his method and I have absolutely no doubt that this method can work (and does work for him).

If you go to the Fermentis website and read the spec sheet for US-05 you will also read:

“REHYDRATION INSTRUCTIONS
Sprinkle the yeast in minimum 10 times its weight of sterile water or wort at 27°C± 3°C (80°F ± 6°F). Leave to rest 15 to 30 minutes.
Gently stir for 30 minutes, and pitch the resultant cream into the fermentation vessel.
Alternatively, pitch the yeast directly in the fermentation vessel providing the temperature of the wort is above 20°C (68°F). Progressively sprinkle the dry yeast into the wort ensuring the yeast covers all the surface of wort available in order to avoid clumps. Leave for 30 minutes, then mix the wort using aeration or by wort addition.”

So, the enquiring mind might ask: why bother with re-hydrating yeast if simply sprinkling the dry yeast will work?
The answer(s) is on the link that @CASK1 provided:

“Most standard 11.5 gram packs of dry yeast contain over 200 billion cells, which is plenty.”

“The same holds true when yeast are introduced directly to wort. Sugars and other compounds are able to pass into the yeast cell, killing it. For this reason, direct pitching is not an ideal situation. A loss of 30% in viable yeast cells, possibly more, could be the result.”

So, a 11.5 gram packet of dry yeast will have 200+ billion yeast cells. If you rehydrate that packet you will have closer to 100% viable yeast cells.

If you simply sprinkle the dry yeast you will have less viable yeast cells (30% loss of 200 billion yeast cells = 140 billion yeast cells).

I believe that Mike is achieving good results in his homebrewing since something like 140 billion yeast cells is sufficient for his homebrewed batches.

I suppose I could be considered a cheapo (but I prefer the word thrifty): my attitude is that I paid for 200+ billion yeast cells and I will take steps to achieve those 200+ billion yeast cells that I paid for. For me, the rehydration process is inexpensive (a cup or less of water costs basically nothing) and the time/effort for rehydration is very easy.

Cheers!

 

Depends on gravity, and I meant I rehydrate as Fermentis suggest. I would still rehydrate anyway as most of my beers are above 1.070 anyway, and if by some chance I didn't I would use (2) packs for anything above 1.060

 

I didn't mean to suggest that rehydrating is a waste of time and/or effort. Only that, when sufficiently fresh and properly stored and handled, 140 billion remaining viable yeast cells (whatever number you believe) is more than adequate for complete, healthy fermentation of a five gallon batch of a 'normal' gravity beer. Sprinkling directly into the wort, as per the package directions, is a perfectly legitimate - and effective - method of using this yeast. If it takes 2 gallons of gas to get you from point A to point B, five gallons in the tank will not get you there any more efficiently or quickly. It only buys you peace of mind - and I won't argue with that benefit.

 

I rehydrate my yeast to see a much quicker start w/ fermentation. Sometimes wouldn't see bubbing for 12+ hours after adding dry yeast. With hyrdrated yeast, usually bubbles after 2-3 hours.

 

If using Go Ferm, a 2 step rehydration and wort introduction is advised: http://www.scottlab.com/product-102.aspx

 

In short, osmosis.

In long, the link by CASK1 above puts it in layman terms.

 

“Can the sugars in that small amount of wort really mess anything up?” Short answer: yes.

Longer answer: read the link that CASK1 provided.

Cheers!

 

'Rehydrating' in wort is virtually the same as pitching it dry.

 

At this point, more yeast won't make a difference. Pitch rate needs to happen when you pitch. Sounds like everything is going fine as is. RDWHAHB.

 

Your beer will be fine. Given what you're observing at this point, I think the chances of it being the best beer you've ever made are not in jeopardy. While yeast handling is an important part of brewing, many people over think it, IMO. The obsessiveness shown by some is simply to ensure some level of overkill. And, in this context, overkill is better than underkill.