# How I Rehydrate Dry Yeast In Ten Easy Steps



## mobrien (5/11/06)

I've seen the questions "how to I rehydrate yeast" asked a few times - so since I'm using a dry yeast today with an aussie ale, thought I would document the process.


*Step 1.*

Choose a good yeast. If you are using a kit, ditch the yeast its probably been in the lid for years and heated/cooled hundreds of times! Buy a good yeast!

Some good brands (and there are others of course!):

Fermentis Safale, Safbrew and Saflager
http://www.fermentis.com/FO/EN/06-Ales/90-10_product_cb.asp

Lalvin a wine yeast manufacturer that does some beer yeasts such as Nottingham
http://www.lallemand.com/Brewing/eng/aboutus.shtm#product

Brew Cellar 
http://craftbrewer.com.au/index.php?page=s...t&Itemid=29


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## mobrien (5/11/06)

*Step 2.*

Find the specifications for your chosen yeast there are usually FAQs, datasheets or PDFs on the website of the manufacturer or supplier.

What you really want to know is What temperature should I rehydrate this yeast at.

For this photo tutorial, well be using a Fermentis Safale US-56.

According to the PDF, it should be rehydrated in 10 times its own volume of sterile water or wort at 27 degrees +/- 3 degrees.


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## mobrien (5/11/06)

*Step 3.*

Find a nice clean container to rehydrate your yeast in. I like to use beer glasses.

*Step 4.*

Clean your glasses, yourself and everything that will come into contact with the yeast. I use Idophor made up in a spray bottle. This means I can spray everything, and know I kill most of bugs. This is sanitising, not sterilising I cant be sure I kill everything. As a note, clean the spray bottle too no point in cleaning everything, and then getting dirty hands from the spray bottle!


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## mobrien (5/11/06)

*Step 5.*

Even though idophor is a no rinse sanitiser, I rinse it out with boiling water when making a starter. Why? I dont want to kill any yeast, and Im using boiling water anyway!

Rinse out the glasses, then drain.


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## mobrien (5/11/06)

*Step 6.*

I like to use a mix of water and wort the argument here is it is easier on the yeast to start, as it is dilute, but you are training it on the actual wort you will pitch it into.

*Edit: 
Please note: Some people believe that yeast should be hydrated only using water, because of the osmotic pressure in a wort solution. I don't agree, so this is the way I do it. You have been warned! For a full description of why you should or shouldn't use wort in the rehydration, there are posts at the end of the steps adressing both sides.*

Fill the glasses with boiling water, and then top up with chilled boiled water to about . 




Then using some wort from the fermenter, fill the glass.




At this point you want to measure the temperature you need a decent thermometer! You are aiming for a few degrees above your target, to allow time to get yourself sorted out.


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## mobrien (5/11/06)

*Step 7.*

Cover the whole setup with glad wrap this stops any airborn bugs! Now wait for the correct temperature.




Since the temp range for the yeast I am hydrating is 27 degrees +/- 3 degrees, it means I can pitch anywhere from 24 to 30 degrees. As I know it will cool during the hour long process, I like to pitch at the top end of this range around 29 degrees. This means over the time it will drop to pretty close to the wort temp.


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## mobrien (5/11/06)

*Step 8.*

Once it is at pitching temp, sprinkle the yeast VERY SLOWLY while briskly stirring the mix. You need to dissolve each individual particle of yeast and not get clumps. It should take about 1-2 mins for a 11g sachet.




After its all dissolved, you probably will get a bit of froth on top 




Now cover and wait for 15-30 minutes.


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## mobrien (5/11/06)

*Step 9.*

You should now have a nice cup of frothing yeast.

After 5 minutes:



After 15 minutes:




You want to stir it about every 5 minutes for then next 30 minutes. By now it should smell, well. Yeasty! You can actually hear it bubbling and watch the froth grow. Ive had these fire so well I have to stir every 2-3 minutes so as not to froth over the top of the glass! Always recover the glass with gladwrap in between each stir you still dont want airborn nasties in there!

After stirring:


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## mobrien (5/11/06)

Step 10.

By now you should have a nice creamy glass of yeast! This may take longer with some yeasts or on a cold day. Open your fermenter, pitch while stirring (pretty much the same as when you dissolved the yeast in the starter) - Remember to sanitise your spoon first (remember the idophor spray).




Close the fermenter and add airlock/blowoff tube. Nowadays I use a dilute idophor solution in my airlocks it is easy to see the level, and if there was any back pressure, the liquid going in should be sanitised. I also leave a tuppaware container of idophor in the fridge to wash/rinse hands etc.




All done hope this is useful!


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## bindi (5/11/06)

I use only pre boiled water to rehydrate dry yeast and start feeding it wort after about 20 min if I have to wait to pitch it.
Something about Osmotic pressure <_< . I will let the *gurus* explain.

Edit: Fermentis Site here on how to rehydrate dry yeast.


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## dr K (5/11/06)

bindi said:


> I use only pre boiled water to rehydrate dry yeast and start feeding it wort after about 20 min if I have to wait to pitch it.
> Something about Osmotic pressure <_< . I will let the *gurus* explain.
> 
> Edit: Fermentis Site here on how to rehydrate dry yeast.




Bindi is quite correct. The idea of rehydating is exactly that, to replace the water by absortion through the cell walls, the osmotic pressure of a sugar solution will cause stress and death.
Ahh...but you say, commercial breweries often pitch dried yeast direct into a sugary wort !!
If you look at the various dried yeast sites (or read the instructions on a 500gm pack) you will find that the pitching rate for ale (assuming fresh yeast) fresh yeast is 1gm per litre and for lagers about twice that so for 25 litres of lager you really need 50gms of dried yeast!!.
Of course you only need one cell of your yeast to start fermentation, its all about competition. Correct rehydration of dried yeast will give your yeast a much better chance.
Anyway mobrien, edit out the wort and you have a great post !!

Kurtz


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## normell (5/11/06)

Thanks mobrien, but is it really necessary to re-hydrate dry yeast ?? :blink: 
I've done 30+ brews, all using Saf yeasts, both Ale & Lager, and always just "sprinkle" onto the wort.
Not one failure yet  

Normell


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## mobrien (5/11/06)

Hi guys - glad I started some healthy discussion! Ok - I'll respond in order

*Bindi and Dr K*

Whilst I understand where you are coming from, I'm not going to edit my post, nor will I be changing my method. This thread was a "this is how I do it" post - its up to you as to how you want to do it. I'm glad you raised your point of view though, as it will hopefully make people think about what they want to do and why.

Just for the record, I will give a rationale for why I do it my way.

As you both quite rightly point out, there is an osmotic pressure because of the sugars and other items in the wort. Wort at around 1.041 is the equivalent of a sugar solution of 67.4g/L. If we do the osmotic pressure calculation for this, we find the pressure is 4.9 atm - that is around 5x normal air pressure.

_<geeky science calculation>

mass sugar = 67.4g
molar mass sugar (C12H22O11) = 342g/mol

therefore n(sugar) = 67.4/342 = 0.197 mol

Because we are talking about 1L (1000mL) the molarity of the solution is the same:

[sugar solution] - 0.197 M or 0.197 mol/L

Using P=MRT we can work out the pressure in atmospheres:

First 29 deg C = 302K

So:

P = 0.197 x 0.0821 x 302 = 4.9 atm

</geeky science calculation>_

This is quite a large pressure! its the same as the yeast being in water 39m deep! And yet, as you know, sprinkling yeast onto wort will work just fine (in fact, as you allude to, it is even on the instructions!)

However, I don't think this is a good idea. It stresses the yeast, and of course decreases numbers. In the end it will work, but I like to play the odds in my favour.

So in my case, I dilute the wort, using a 1:2 dilution, water to wort. Now using the same geeky calculation as above, but this time with 22.46g of sugar (1/3 wort), we find the pressure is now 1.6 atm. Now this is only the same as the yeast being 6m deep in water (coincidently about the size of the big industrial fermenters).

It still is a positive pressure on the yeast, but one I am willing to put up with - why? Well, yeast use both oxygen during aerobic respiration, and sugar during anaerobic respiration. Whilst we want aerobic respiration during the rehydration, as this encourages multiplication, it is very easy for the yeast to remove all the oxygen. When this happens, I want them to have a food store - and I have a choice - I can use DME, sugar or wort - I'll use the wort any day of the week.

Anyway, that is the logic and the science behind the way I do it - and it works for me!

Matt


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## mobrien (5/11/06)

And now to reply to Normell,

Sprinkling the yeast over the top will work fine any day of the week. I've done it many times, and like you have never had a failure.

However, rehyrdating the yeast in a more favourable environment will get the active and ready to go a lot faster. This is for two main reasons. The first is they have absorbed the water, and so come "back to life" - when you add them to the wort, they are ready to go and more survive. The second (if you add sugar or wort either at the start or pretty soon into the rehydration process) is that you get the yeast reproducing (or well on the path to reproducing) before they hit the wort, so again, numbers increase.

A case in point - the two hydrated yeasts I made this morning for this thread were added at 10:00am or so. The airlocks were bubbling by 11:30. Dry yeast (in my experience) takes around 6-12 hours to do the same.

M


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## normell (5/11/06)

points taken onboad mobrein, will buy a thermo tomorrow, and do your method for my next brew.
this Homebrewing caper is all learn, learn and learn some more  

Normell


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## Ross (5/11/06)

Adding wort will work, as will sprinkling dry, but for maximum viability & health of your yeast, JUST REHYDRATE WITH WATER. 

cheers Ross...


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## dr K (5/11/06)

Ross said:


> Adding wort will work, as will sprinkling dry, but for maximum viability & health of your yeast, JUST REHYDRATE WITH WATER.
> 
> cheers Ross...



Ross
In one single line, what would have taken me 5 paragraphs !!!!

k


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## mobrien (5/11/06)

But why? Where is your data?

For now, I'll keep on doing things my way - I'm happy to have my opinion changed, but "just do it this way" with no explanation or data won't go any way to changing my mind.

So I propose an experiment:

24 x 250mL conical flasks
4 concentrations of sugar - 0g/L; 22.4g/L; 44.8 g/L; 69.2g/L
4 packets of yeast
bung and delivery tube for each flask, to inverted water filled measuring cylinder

Pitch 1/3 pack of yeast (equal weight to 3 dec places) in each flask on 100mL fluid. 3 replicates of each treatment - i.e. 3 flasks 0g/L sugar; 3 flasks 22.4 g/L sugar; 3 flasks 44.8 g/L sugar and 3 flasks 69.2g/L sugar.

Measure the volume of gas produced over the rehydration time - since CO2 gas production is a known measure of yeast activity. This will tell us which one is the best for rehydrating.

After 1 hour, pitch 10mL of each of the hydrated yeast into 200mL of 69.2g/L sugar solution, and continue to measure CO2 gas production. 3 replicates of each again. This will tell us which is the best over time for fermenting.

I have the equipment to do this at work - so before I do, do the "anti wort" people have any problems with the experiment? What yeast should I use?

M (willing to test it all)


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## bigfridge (5/11/06)

mobrien said:


> But why? Where is your data?
> 
> For now, I'll keep on doing things my way - I'm happy to have my opinion changed, but "just do it this way" with no explanation or data won't go any way to changing my mind.
> 
> So I propose an experiment:



Mobrien,

No need to test your theories as the research has all been done before by a leading yeast authority. See here for a full description of what happens when you re-hydrate dry yeast and why you should not use wort for the best results.

David


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## Lindsay Dive (5/11/06)

Try Fermentis K-97.....only joking.
I reckon the test would be real interesting....go for it....use SO4.

Regards,
Lindsay.


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## beers (5/11/06)

bigfridge said:


> mobrien said:
> 
> 
> > But why? Where is your data?
> ...



Nice article David. 
It's a shame that he doesn't elaborate on the "Very dilute wort seems to be OK." comment.


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## mobrien (5/11/06)

bigfridge - thanks for the data! The nice quote I think is:

"The water should be tap water with the normal amount of hardness present. The hardness is essential for good recovery. 250 -500 ppm hardness is ideal. This means that deionized or distilled water should not be used. Ideally, the warm rehydration water should contain about 0.5 - 1.0% yeast extract. 

For the initial few minutes (perhaps seconds) of rehydration, the yeast cell wall cannot differentiate what passes through the wall. Toxic materials like sprays, hops, SO2 and sugars in high levels, that the yeast normally can selectively keep from passing through its cell wall rush right in and seriously damage the cells. The moment that the cell wall is properly reconstituted, the yeast can then regulate what goes in and out of the cell. That is why we hesitate to recommend rehydration in wort or must. Very dilute wort seems to be OK. "

The tests might be worthwhile afterall, if very dilute wort (the question of this thread!) "seems to be ok"!

M

Edit: I can't smell


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## wessmith (5/11/06)

And as I have posted on several occasions in the past, Lallemand and Fermentis use very different drying techniques in their respective production processes. That is why Lallemand say "only use water" and Fermentis says "water or wort". Why not believe the manufacturer! I can tell you that we ALWAYS use wort when rehydrating Fermentis products. Pitching rates are usually 60-70gms/HL for ale yeasts and 100-120gms/HL for lager yeasts - unless of course you want to develop some distinct ester characteristics when we pitch around 70% of those values to get a longer lag time. 

In 800ltr and 1000ltr brew lengths we find terminal gravities for the ale yeast styles achieved in 3 to 4 days at 18C and 6 to 8 days at 10C for the lager styles.

Mobrien, measuring CO2 production may not be all that accurate as the respiration rate of yeast will depend on the pitching rate and the corresponding lag time - ie how long does the yeast take to multiply before getting on with the task of making alcohol.

Of course all of the above assumes that you have the optimal environmant for the yeast to ferment properly. Any shortage of nutrients will skew the results. Interesting that Dr clone stresses the need for a certain calcium level in the rehydrating water for his companies yeasts. You will of course find those same calcium levels in wort.....

Wes




mobrien said:


> bigfridge - thanks for the data! The nice quote I think is:
> 
> "The water should be tap water with the normal amount of hardness present. The hardness is essential for good recovery. 250 -500 ppm hardness is ideal. This means that deionized or distilled water should not be used. Ideally, the warm rehydration water should contain about 0.5 - 1.0% yeast extract.
> 
> ...


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## Ash in Perth (5/11/06)

This probably isnt practical for homebrewing, but dry wine yeasts acheive the greatest viability when re-hydrated for 15min at 40DegC then cooled down to pitching temp. Its odd that those kinds of temperatures can be lethal to yeast.


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## Adamt (5/11/06)

I currently rehydrate with a procedure that is a mix of the opinions expressed.

I first pitch the yeast into stirring warm water, cover for 20, then add a small amount of wort.

This way I'm rehydrating with water preventing sugar entering the yeast cells, and then preparing the yeast for the wort I'm putting it in.

Awesome post mo!


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## Kai (5/11/06)

wessmith said:


> And as I have posted on several occasions in the past, Lallemand and Fermentis use very different drying techniques in their respective production processes. That is why Lallemand say "only use water" and Fermentis says "water or wort". Why not believe the manufacturer! I can tell you that we ALWAYS use wort when rehydrating Fermentis products.



Can you expound a little on this please, wes? I am too lazy so search the respective sites, and it seems so different to the basic knowledge I have at this point regarding any dried yeast.


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## Screwtop (5/11/06)

If we took a rock with a hole through it and put a log through it, then ran it along the ground until the edges wore off, this round thing could be very usefull, I have a name to call it, how's about "The Wheel"


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## bigfridge (5/11/06)

Kai said:


> wessmith said:
> 
> 
> > And as I have posted on several occasions in the past, Lallemand and Fermentis use very different drying techniques in their respective production processes. That is why Lallemand say "only use water" and Fermentis says "water or wort". Why not believe the manufacturer! I can tell you that we ALWAYS use wort when rehydrating Fermentis products.
> ...



Kai,

The specsheets are available for SafAle US-56 and SafLager 34-70 at the Fermentis website. 

David


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## mika (5/11/06)

I'm with MO...had too many yeasts not take off making me panic and pitch a second yeast.
My 2c anyway.

P.S. Slowly moving towards liquid yeasts so will stay out of these arguments in the future


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## Slurpdog (5/11/06)

Seems like Adamt has taken the science of both methods and combined both their advantages.
I've never re-hydrated in the past but will rehydrating give a better chance of a lower FG?
All my beers seem to finish quite high (1014-1018) with an average OG of about 1050-1052.
If this re-hydrating caper will acheive a lower FG then I'll definitely give it a go!


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## mika (5/11/06)

Yeast may not be to blame for your high FG...look closely at the fermenables in your brew


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## Brewtus (5/11/06)

This may be a little left field but when I bake if I rehydrate the yeast in luke warm, 25deg, water the bread/dough/whatever raises quicker. If I throw in a pinch of sugar, it is even quicker still. Even though it is not some super special beer yeast, ie defiance, it is still saccharomyces cerevisiae, ale yeast, and should react the same. 

FTR I do not use wort when baking nor baker yeast when brewing and in all cases prefer to rehydrate when I can..


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## Darren (6/11/06)

I think the only reason to re-hydrate in a seperate smaller container is to ensure the yeast is still alive. If it don't bubble don't use it.

cheers

Darren


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## Sammus (13/11/06)

Adamt said:


> I currently rehydrate with a procedure that is a mix of the opinions expressed.
> 
> I first pitch the yeast into stirring warm water, cover for 20, then add a small amount of wort.
> 
> ...



Exactly what Lord Palmer recommends, and I'm guessing for the reasons indicated in this post and thread.

For the record, I do it this way was well (when I use dry).

Edit: and doubley for the record, doing it with water is rehydrating, doing it with sugar/wort is proofing (as I understand anyway)...


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## Kingy (27/2/07)

Hi i need a little help :unsure: 

just tried to rehydrate yeast for the first time.

filled my schooner glass up just over half way with cooled boiled water to 28 degrees added the yeast that comes with a coopers kit stirred every 3 mins and 1 hour later nothing has happened except me drinking more beer and staring at it.

1.what have i done wrong

2.is it still ok to add to fermenter

3.should i put a little dextrose in there

4.should i halve it bcoz i filled the schooner up to much and add a little dextrose to the halved glasses

5.i dunno

6.drink more beer and wait.


p.s i think this thread has confused me

7. ditch the whole lot and throw a spare yeast into the fermenter.

8. maybe through the failed rehydrating exercise yeast in and also throw a differant yeast in all together (blu mountain lager and a coopers lager yeast?)


edit.add 8th step lol


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## lonte (27/2/07)

Kingy said:


> 2.is it still ok to add to fermenter


yes.


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## Kingy (27/2/07)

doesnt matter FFS i rehydrated my yeast in an empty schooner glass that i just finished drinking from grrrr.... and the iodopher soaked glass is just sitting there. Looks like this one is gunna taste like crap.

doesnt matter i brought the coles brand for the first time ever just to see if it turns out better than a brew shop brand. looks like its gunna taste like shit. im cursed by coles.

Waiting on my 2 keg setup to arrive,was due to arrive today im not gunna put this in the kegs ill bottle this ruined one and get some proper stuff tomorrow and brew a decent kit for the kegs.

i think i was cursed

im getting sick of k+k its not challenging enough and i fall asleep doin it. Now my kegs are nearly here AG is looking the go.


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## Keifer (27/2/07)

Some good reading on different approaches to yeast re-hyrdation.

Kingy, if your sick of kk coz it's not challenging, are you doing specialty grains and hops with em ?


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## PistolPatch (27/2/07)

I wrote this email to someone a few months ago so might as well throw it into the ring. This gives you something to do while brewing in case you arent drinking. Only has 9 steps though 

*Creating A Mini-Starter including Rehydration of Yeast*

You Will Need

1 x Sachets of Yeast
1 x Coffee Mug
1 x 250ml Pyrex Jug
1 x 500ml Pyrex Jug
1 x 750ml Bottle with Lid or larger (e.g. soft drink bottle)

Directions

1. Prior to Mash In: bring a half kettle of water to the boil. Leave to cool.

2. Duriing Mash In: Ensure jugs, mug and bottle are clean and then sprayed with no-rinse sterilizer. Cover them with plastic.

3. At Boil Start: By this stage the boiled water should have cooled 25-30 degrees. Until you can judge this by touch, use a clean thermometer that has been sprayed with no-rinse sanitizer. If the temperature falls within the 22-32 degree range then pour 110ml into the 500ml jug. Sprinkle the 11g sachet of yeast onto the top of the water. Do not stir. Cover with fresh plastic and let it sit.

4. 5 Minutes After Start of Boil: Regardless of whether you have added your boiling hops or not, remove a mugful of wort from the kettle. Pour 250mls into the 250ml jug to half fill it. Cover with plastic and place in a sink of 25 degree tap water. 

5. 20 Minutes After Start of Boil: By this stage hopefully your yeast will have formed a milky solution with a creamy head. Often it wont. Dont worry, just continue as follows. Remove the 250ml jug of wort from the sink. As you did in Step 3 above, ensure the wort is in the 22-32 degree temperature range. Add 40mls of wort to the rehydrated yeast in the 500ml jug.

6. 30 Minutes After Start of Boil: Add another 80mls of wort to the 500ml jug.

7. 40 Minutes After Start of Boil: Add remaining wort to 500ml jug.

8. 60 Minutes After Start of Boil: Pour the entire contents of the 500ml jug into your bottle. Screw on lid and shake. Release pressure and repeat occasionally until wort has chilled.

9. Chill End: Pour bottle contents into bottom of fermenter and syphon in wort. Or vice-versa! (Who knows)

P.S. Thanks Screwtop for the bottle shaking idea. The above seems to get things happening very quickly.


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## Kingy (27/2/07)

Keifer said:


> Some good reading on different approaches to yeast re-hyrdation.
> 
> Kingy, if your sick of kk coz it's not challenging, are you doing specialty grains and hops with em ?



nah still aint worked it out yet :unsure: 

therez some good threads on AHB but there are so many differant oppinions on "the next step" so to say threads, that it throws me in a distorted heap. and it just loses me.

ATM All Grain sounds easier to me. and id rather jump straight to doing that.

coz i know in the long run im gunna end up doing that anyway.

im only 24 as well so if start now, by the time im 30 i should be killin it. :super:


edit: spelling


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## MHB (27/2/07)

I sell something like 50-100 specialty dried yeasts a week (not the ones under the lids - Saf, Muntons, Brewcellar etc); on thing about being a retailer, everyone's problems are my problem.

Over the last couple of years I have received feed back from literally thousands of customers; the concessus observation is this.

*The only people who have any problems with dry yeast are the ones who rehydrate.* 

I am not suggesting that there are no benefits to rehydrating, just that if you just sprinkle the yeast directly onto a wort at the correct temperature you won't have any problems.

From the Fermentis website for US-56 the rate is 50g/hL, or 50g/100L; 12.5g/25L, either rehydrated or added directly with agitation (aeration).

Tho I prefer not to have unhappy customers, if someone wants to rehydrate yeast the steps mobrien outlines would work, the thermometer is the one critical piece of equipment that most would be yeast wetters leave out of their kit - and it doesnt take much heat to kill the yeast or to reduce the benefits that may be gained from rehydrating.

Be very careful or KISS - the simple way works every time.

MHB


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## warrenlw63 (27/2/07)

I have a "slightly" unorthodox method. Involves 1 x sanitised mason jar and 1 x sanitised plastic (or whatever) spoon. 

Note: Sort of for no-chill brewing but could be utilised regardless.

I add 500ml of the wort I'm going to pitch to the mason jar, open the yeast sachet and sprinkle on top of the starter wort. Leave it sit for 15 mins. Stir lightly with the sanitised spoon. Leave another 15 mins then shake the living shit out of the mason jar to mix, knead, distribute the dried yeast to the wort. After the shake the mason jar of wort looks like a milkshake. My aim here is nothing more than to break up the dried yeast clumps that sit about the liquid level etc.

Then I just add it to the fermenter(s) and it kicks off nicely after 6 hours or so. :chug: 

Edit: Added a bit.

Warren -


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