Like everything else in brewing, there isnt necessarily a fixed rule on how to do it, there are probably different opinions on it, you just need to understand the processes and decide what has the least risks for your situation. What I do and probably is most common is drop the beer onto the dissolved sugar solution, give a gentle non-aerating stir and bottle immediately.
Posssible advantages of waiting 60 mins would be
-density and chemically driven motion should improve the mixing of the sugar through the beer and may give slightly more even carbonation
-the yeast will have a chance to start on the sugar and generate a little CO2. When you put the beer in the bottle, the headspace will maybe have a bit more CO2 to protect the beer by the time you cap it.
The main risk might be the potential for something nasty (wild yeast, bacteria, insects, oxygen, my dogs tongue) to get into the beer while in the 2nd fermenter, especially since there wont be much of a CO2 blanket on it.
So I would think the risks outweigh any potential advantages, and would bottle immediately, get the beer safely protected in the bottle.
Another reason to bottle immediately would be if the beer has been cold conditioning. If you let the beer warm up, dissolved CO2 will come out of solution, and the bottling process gets foamy and messy.
Yeah I agree the risks are low, but since I havent had a problem with uneven mixing for me there isnt much advantage in waiting. About the first 40 or 50 times I bulk primed, I didnt even stir and bottled immediately. Then I finally experienced the dreaded uneven carbonation so I'm a stirrer now.
OK, I'm gonna be the guinea pig here... I have always bottled immediately on bulk priming as I thought the beer would be best mixed at this initial point having been 'swirled' from the wort hitting the priming mixture on the bottom from the bottling tube. I'd have thought the longer you left it, the greater the chance of the dextrose/malt mix sinking to the bottom of the fermenter and producing uneven secondary ferments. Please feel free to point out just how wrong I am...
Like GMK says I rack to 2ndry and dry hop for 2 weeks or so.
Then rack to the bottling fermenter.
Make sure the priming sugars are well disolved first, add them first then rack the brew via a racking tube that reaches the bottom of the bottling fermenter. Creates a swirling, slow cyclonic motion which seems to mix the beer and priming solution pretty well. Bottle pretty much straight away.
Never had a bomb since I've been doing this, nor a flatty.
The racking tube action does a pretty good job of stirring the brew - don't see why I should waste any of my energy.
If you have reasons for me having a better workout, please let me know.
The major reason for the half hour standing period is simply because others have reported the swirling motion isn't enough for them. You haven't had problems, that is fine, but others have. I don't want to be on the receiving end of a 'YOU TOLD ME TO BOTTLE STRAIGHT AWAY AND NOW MY BOTTLES ARE BLOWING UP' in a months time.
Experience is the best way to work out what works best, but when giving advice I tend towards the safer end. The sugar solution won't sink as it is in solution. Adding it to the beer simply dilutes it.
Edit: JM, I always boil my priming sugar now, but never had any problems when I didn't. I usually put it in the microwave for a while.
Rack the beer into your secondary and cold condition for a couple of weeks (dry hop if you want to at this time)...
When you're ready to bottle, make your priming solution (I usually mix dextrose, really well, into a clean jug full of just boiled water but I will have a go with Wheat DME next time ) and pour into the bottling bucket / tertiary vessel.
JM - Does the Wheat help head retention as well as carbonate?? Same quantity of Wheat DME as Dextrose? I usually prime with 160g of dextrose for 23L of pale ale...
Do the cyclone thing ?! and I've NEVER had to stir to get a good mix and I've NEVER had a bottle bomb since 1995, nor have I had a "flatty"...Guess I've got the caper sorted out
The bulk conditioning helps improve the wort substantially, IMHO, rather than putting the wort into small vessels (ie, bottles) and letting it fight the fight in smaller quantities...Safety in numbers, yada yada...
My only concern (and this my own dead reckoning, not scientific analysis) is that if I make, say, a porter or something nice and hearty, would I be overdoing the brew if I prime with something that doesn't completely ferment out, like dextrose?
I always figured that priming with dextrose was a nice neutral solution and if I needed to worry about head retention or body of the beer, then I should be fixing the recipe and not trying to do something at the last minute, ie, use malt in the priming solution..