Just be patient, or...

I brewed a 10gal batch of scotch ale 3wks ago, OG 1.078. I pitched the yeast cake of a 600ml starter of WLP004-Irish Ale yeast divided into each 5gal half. Fermentation temperature was around 60-62 degrees. That is the temperature of my floor which is a slab on grade foundation. After 10days, I assumed it was done fermenting, because most all of my beers have been done after 10days. After racking, I took a gravity reading. One carboy was at 1.040 and the other at 1.030. The 1.040 half, I left at 60 deg and after a few days, it didn't change. I then warmed it up to 70-71 and after 3 days, the gravity was at 1.035.

My questions are:

1) should I continue to have patience, or try a little yeast energizer?

2) I don't currently have a yeast cake from a fermented batch, but if I end up needing to rack it onto a yeast cake, would a lager yeast work? Since it is winter and I can find a cool place to ferment, I was thinking about brewing a bock or dopplebock for the spring.

You need to raise your temps up a bit. At 60f, it will take a lot longer to ferment.

You WAY under pitched. A single 600ml (.6L) starter isn't enough for 5 gallons of 1.078, not to mention 10 gallons. With a starter you shake as often as you walk by Mr. Malty calls for almost 4x per 5 gallons. You're going to need to repitch and try to save it.

Under-pitching just means it takes a long time for the yeast to get to the right population. It will eventually getthe job done.

I'd go with the low temperatures. Up the temperatures (not really clear, but you seem to have done that), and somehow rouse the yeast (gently swirl the fermenter).

I'm going to agree with Calder. Underpitching won't cause a stalled fermentation, it just takes a few extra days for the yeast to get up to healthy numbers.

Suthrncomfrt1884 said:

I'm going to agree with Calder. Underpitching won't cause a stalled fermentation, it just takes a few extra days for the yeast to get up to healthy numbers.

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No but racking early (FG of 40) and under pitching is going to to stall it.

I disagree. Underpitching leads to yeast that are more stressed out. They have to use a greater proportion of nutrients for cell division rather than fermentation. Then they get to the fermentation stage and are nutrient deficient. Underpitching absolutely leads to stuck fermentations.

If you look through all the threads on HBT with "stuck fermentation" in the title, I'd guess that in at least 80% of them the problem was underpitching.

Might want to pick up a couple packs of S-04 and chuck them in (after rehydrating of course). I'd shoot for a temp closer to 64-65 if possible.

I was getting ready to brew a SMaSH pale ale with Simcoe hops, but I was hoping to brew a lager next, so I had the idea to call the brewer from a local microbrewery who has been helpful in the past. He gave me 20 oz of yeast from the bottom of a fermenter that had just finished. I dumped that into my corny's. I'll post follow up when I have the final results