Doing my 2nd batch (after a break of 20 years :) ). Its a LME / DME porter attempt. It all went according to plan and the OG = 1045. It started fermenting more or less on time, but was sluggish from the start. From what I can see, it only built up a krausen of max 1cm. It was blubbing nicely for a few days but has slowed down now at 72 hours. Just took a sample (have a tap on the fermentation vat, so no disadvantage to doing so) and it's still at 1030. I haven't found any info or rules of thumb indicating where it should be. The yeast was a M42 New World Strong Ale Yeast. Should I repitch, or will I hit 1010 - 1015 with a few weeks of fermentation + bottle conditioning?
Firstly, welcome back to the world of home brewing.
Dried yeast during re-hydration are sensitive, but a little gentle shaking will not ruin the viability.
I would leave it for about 7 days from pitching if you are no where near FG by then, then make a small starter and pitch that. Once there is alcohol in the mix you really want to make a starter to ensure your dried yeast are most importantly re-hydrated when re-pitching. As if they are not the alcohol can diffuse quickly through the dehydrated cell walls and damage the cells. This is less critical with liquid yeasts.
There are a few things that may be affecting the fermentation:
- is the wort sufficiently aerated?
- was the yeast nice, fresh and well stored?