Can SG get lower after 10 days?

[Vetal]

So I did my third batch with borrowed, on hand ingredients plus a few extras. A friend had a 2 month old liquid yeast from "Escarpment Labs" - Irish Ale Yeast which he was not planning on using... so I thought I would use it with some roasted barley and cara 85 I had on hand. I used an Irish Red recipe and modified it.

1 lb of Maris Otter Pale Malt (grain)
1/2 lb of Cara 85 Malt (grain)
1/2 lb of Roasted Barley
3 lbs of Pale DME
3.3 lbs of Light LME
1 lb of Caramelized Table sugar

Escarpment Labs Irish Ale Yeast (2 qt starter - on stir plate for 18 hrs)

45-50 mins grain mash at 145-160 range (dont have the equipment to hold the temperature precisely) - to get a "grain tea"
60 mins boil with 1 oz East Kent Golding (4.7 AA) (~ 3 Gallons)
Whirlpool Hop Addition @170 of Amarillo Hops (12.7 AA)

I had some challenges cooling the wort down... even after leaving it in a snowbank @ 30F for 30 mins - my wort was still hovering around 90+F. I added approx 2 Gallons of RO water to bring the wort to 5 Gallons... this brought my temp down another 10F.
I used a cheap refractometer as I couldnt find my hydrometer. As far as I can read (eyes arent as good as they used to be ) ... the OG was 15 Brix (approx 1.065) - which would be fairly close to the expected value.
I pitched the yeast starter at a wort temp of 80F... ambient temp of yeast was around 68F. Almost within the hour - I had vigorous bubbling in my airlock.... but 24 hrs later there was almost no activity anymore.
After almost 10 days - I finally got around to taking the SG reading using the same refractometer. It is reading approx 9 Brix... I used the refractometer reading calculator with a wort correction factor of 1.040 to get an ABV of approx 5.2%.

My fermenter was sitting in my basement @62F - so I have brought it upstairs with ambient temp @ 68F. So - all good - looks like I am in the range of what an Irish Red should be. BUT - I had expected that my ABV would be around the 6.2% range based on an online calculator.

Question:
- I hear that the refractometer is fairly accurate for OG readings? Is that correct or should there be a Wort Correction Factor applied?
- I had aerated the wort, added yeast nutrients, created a starter etc - so I was expecting fairly healthy yeast... Still - why is my ABV still 1% lower than the expected value?
- Can I expect the SG to drop further over the next week or so?

Thoughts/ advice greatly appreciated - THANKS All !!

 

[McKnuckle]

You can't use a refractometer for gravity readings when there is alcohol present. Go to this calculator, which will help you estimate the actual gravity (given the pre-fermentation OG):

https://www.brewersfriend.com/refractometer-calculator/

P.S. This mistake is extremely common.

P.P.S. Don't try to determine ABV from the refract scale. Calculate ABV using your OG and FG measurements.

 

[bucketnative]

A refractometer is fairly accurate for OG readings

Refractometers are not terribly accurate at determining the SG once alcohol is in the mix. You can get an OK correction using one of the sites out there, but as @balrog recently demonstrated (https://www.homebrewtalk.com/forum/threads/first-time-this-has-happened.674492/#post-8769253), it is not 100 % linear in its relationship with a hydrometer reading. Note the variability between "FG-h" and "FG-calc". Also note, that he stated that his measurements may not be totally accurate, but that just speak to the variability involved in all of this.

Every ferment is different, especially without accurate temperature control. The rule of thumb is that a stable SG over three days indicates fermentation has finished (there are exceptions to that rule, though... stalled fermentations).