Do I need more yeast?

I am brewing a barley wine that has an OG around 1.100. I determined initially that I needed 4 million yeast cells. I pitched the wort on top of a yeast cake from a previous brew. I'm not sure if fermentation is complete although it seems to have stopped. If in doubt, should I add more yeast or should I leave it alone?

 

Current gravity is about 1.04 and holding.

 

do you mean 4 million cells per degree plato? a yeast cake has 500 billion or more cells. in any case, if you pitched on top of a complete cake, i doubt you will get any more attenuation than what you've already got. 1.04 is awfully high, though.

 

How long has it been since you pitched? How are you determining that fermentation has stopped? Are you measuring the current gravity with a refractometer? What temperature are you fermenting at?

 

It's been fermenting for 9 days. I am using a refractometer which I am a little suspect of. I'm stating that is stopped fermenting because it stopped bubbling, and it's cleared up considerably. I plan on checking the gravity again to confirm.

 

It's been fermenting at around 64 degrees.

 

This is what I suspected when your gravity reading was so high. Refractometers are a wonderful tool when used at the right time. When you are brewing all grain you can grab a sample of hot wort and use the refractomenter because the drop or 2 of wort you need will chill pretty quickly so you get an immediate reading.

However, once you get alcohol involved, the reading gets skewed from that so without using correction tables, you get an incorrect reading. You should only use the refractometer on brew day and once you have pitched the yeast switch to using a hydrometer. Your 1.040 refractometer reading is much higher than the actual gravity.

 

I'll use a thief and a hydrometer and check it again. Do sanitize and pour the beer back into the ferment or or do you dispose of after the reading? I'm a pretty frugal guy and I hate the thought of tossing out potentially good beer; even just a few ounces 😢.

 

i find the refractometer to be useful on brewday, like for checking pre boil gravity w/out waiting for wort to cool, but not so much when checking FG. try a hydrometer instead.

for a while i was using a sanitized thief and returning samples to the beer. now i draw them with a thief but then toss them or drink them. for me it isn't worth the risk of contamination