Delayed pitch, no ferment?

Hi all - after a normal brew session last night, 4th so far, a minor kid crisis (don't ask - haha) prevented me from icing down the wort to pitching temperatures. I ended up leaving the wort to cool in the primary with an airlock on it. This morning it was at temp so I pitched (smack-pack) and aerated with the usual shake and whisk. 12 hours later and zero activity, which is a first for me. Assuming the yeast is fine (@ 6 months old, I wasn't surprised to see only minor bulging in the pack after an overnight sit), is it generally considered a no-no to let the wort sit for ~10 hours after brewing?

Thx!

Supposedly doing it that way (cooling the wort down gradually) will prevent the cold break and could possibly cause a little cloudiness in the beer, nothing really to worry about though. It sounds like you had it sealed for the most part so it shouldn't have been contaminated.

As long as it doens't get contaminated, its houldn't be a big deal if it sits for that long.

As well the slow cooling could cause DMS.
I make a starter for my smack packs at least 4 days in advance of brewday. It just gets things moving faster.
Just wait it out. The low yeast count will wake up if you aerated good enough and things should be bubbling by later today. I have waited up to 48 hours for things to start working before pitching a pack of dry yeast to jump start my brew.

Your problem was leaving your smack pack till the last minute, and pitching it while it was still half asleep. The small amount of yeast that were active are now using your wort as a giant 'starter' trying to reproduce as fast as they can.

If the pack is not fully swollen, then it's not ready. The manufacturer states that you should count on 1 day for every month since the date it was made.

Even better, next time make a starter a day or two ahead of time to avoid the lag.

Your beer should be fine.

Thanks all - and yes, I wasn't exactly on the ball this time. Had one of those 'oh crap I was supposed to brew tonight' moments. No starter, half-done smack pack, no rapid cooling....not my best effort.

The primary is currently sitting in my cool basement (60's) per the recipe, but I think moving it to a warmer place will help get things moving. If I still don't have any visible activity (airlock or surface foam) after 24 hours at 70deg, is it still recoverable with repitching with a good starter? The wort will have been sitting for several days without a nice CO2 layer on top (though this is a decently hopped brew). How long until an unpitched wort to goes 'stale'?

Thanks again!

I would re-pitch & move it to a warmer location until the fermentation starts. Since the yeast don't switch to making alcohol until they have consumed all of the O2, there won't be any change in the final flavor.

The main problem with slow cooling is bacterial infection in the 90-140F range.

As usual in homebrewing, patience is rewarded: first gurgles are appearing tonight, just 36 hours after pitching . I moved it to a 70 degree location, and hopefully we'll be a-rockin' soon. Thanks again to all for the advice.