Understanding FG

[Spud395]

I think I have this right in my head, just need to cheak.
My 1st AG went into the fv last Sat.
With an OG of 1.059
Last 2 days its reading 1.020

Beer Engine gave me a OG of 1.057 and a FG of 1.017, so I guess I'm not far off those figures.
I had only ever brewed kits before and allways got down to around 1.010/12, however I allways had lower og than this brew.

Am I right in thinking with the higher gravity to start, there will be more unfermentables?
I discovered on brewday that my thermometer wasnt really up to the job, as a result I'm not 100% on what actual mash temp I had.

My boiling wort showed up as 95deg on the thermometer, if it was 5deg out all down along this would have given a mash temp of 61deg.
I thought this should have given a really fermentable wort, but I just dont know what is the story with the thermometer.

Anyway I roused the yeast a little today and am in no hurry to bottle, it still might drop a point or two.
But am I thinking along the right lines?

[coatesg]

Am I right in thinking with the higher gravity to start, there will be more unfermentables?

Generally yes, though expected FGs are different depending on what yeast strain, how much sugar you use, etc. For something like S04 in a bitter, I generally assume about 70-75% apparent attenuation - good aeration helps a lot.

Either way, 1.020 is a little high, but it has only been 6 days or so, so I'd give it at least another 4 days to see what it does - you can try rousing if you want to see if it'll go another point or 3.

[Jolum]

Couple of things.

Am I right in thinking with the higher gravity to start, there will be more unfermentables?

One word Belgiums. Apparently they get up to 95% attenuation. There are lots of factors that can create a less fermentable wort - grain bill (as you say higher OG but if most of that OG is sugar it'll ferment just fine ergo why I mentioned Belgiums ), mash temp, attenuation capacity of the yeast used etc.

My boiling wort showed up as 95deg on the thermometer, if it was 5deg out all down along this would have given a mash temp of 61deg.

Have you confirmed your thermometer readings? I have 7 thermometers (of different types) and only 2 of them are within a degree of each other

--EDIT Damn Coatesg beat me to it by a minute...must type faster

[coatesg]

One word Belgiums. Apparently they get up to 95% attenuation.

My thoughts exactly - it's the high sugar percentages and the rampant yeast strains they use!

On the other hand, something like Windsor has lower attenuation than other strains and so you'd expect a higher FG.

[Eric]

I'd be happy with those gravity readings. As you say, they aren't far from the predicted.
Your boiling wort would be higher than 100C due to its sugar content so your thermometer was reading more than 5 degrees LOW. IF it reads low throughout its range then the mash temperature would be HIGHER than your thermometer reading and would give less fermentable sugars.
I'd keep it covered and leave it well alone for the best part of a week trying to keep it cool. Looks very much like a winner.

[Spud395]

Pretty much as I thought lads thanks, got my mash temp thoughts backways allright.

She's sitting at 18deg for the past week and Saturday is allways my day for brew related doings, so it's got another 7 days to sit

[brewzone]

For a 1.059 OG wort I'd be bottling at around 1.015 so long as this FG had been observed for around a week.

I remember reading a Graham Wheeler post some time ago where if kegging He talks about racking to keg slightly higher than the required FG and allowing some pressure to build up in the keg.

This pressure is then realesed which has the effect of removing some of the unwanted volatile compounds along with the CO2.

[Bobba]

You can try raising the temperature up a to 20C or so to help the yeast along a bit further.