Not Hitting OG in my BIAB

[J A]

I use my refractometer to measure wort during mash. That way I can track changes and estimate when I'm maximizing conversion. To get a gravity reading for making calculations, I'll get a hydrometer reading. And, as I mentioned, I only use the gravity reading and accurate volume measurement after boil to calculate actual efficiency and OG. If you don't know anything other than SG before and after fermentation, it'll tell you about the attenuation and the alcohol content. Accurate volume readings are important for setting equipment profiles, tracking efficiencies and building recipes accurately.

 

[Donoroto]

@Northshore I have the same one, and under the right conditions it is very close to the hydrometer.

 

[Zambi]

[double post]

 

[Zambi]

Even if the reading was quite far out compared with a hydrometer, I wouldn't throw it out.
I use it to see if the fermentation has finished. Basically all I need to know is if the reading stays the same for a couple of days running.
I do small batches and would hate to have to throw out that hydrometer sample liquid everytime I check

 

[Nosybear]

Even if the reading was quite far out compared with a hydrometer, I wouldn't throw it out.
I use it to see if the fermentation has finished. Basically all I need to know is if the reading stays the same for a couple of days running.
I do small batches and would hate to have to throw out that hydrometer sample liquid everytime I check

Yep. You can use the conversion formulas to get an exact (within 0.001 SG) FG but if you're looking to see if fermentation is complete, all you need to look for is change.

 

[Northshore]

That's a good point and I doubt I would pitch it unless it truly was useless. I did get myself a Tilt hydrometer (Christmas present to myself) and that has been excellent for tracking temperature and watching the graph for gravity.

Even if the reading was quite far out compared with a hydrometer, I wouldn't throw it out.
I use it to see if the fermentation has finished. Basically all I need to know is if the reading stays the same for a couple of days running.
I do small batches and would hate to have to throw out that hydrometer sample liquid everytime I check

 

[Silver_Is_Money]

If you know your mash efficiency for a given pre-boil specific gravity (PBSG), you can get a rather decent ballpark of your expected mash efficiency at other PBSG's as follows per this simple empirical relationship I've come up with:

Example:
Known: Whenever I brew batches with a pre-boil SG of right close to 1.043 I tend to quite often average a mash efficiency of ~76%
Unknown: What will my mash efficiency be for a pre-boil SG of 1.057?

Anticipated Mash Efficiency = Knowns_Efficiency x (1+(Knowns_PBSG - Unknowns_PBSG) x 3.35)
Anticipated Mash Efficiency = 0.76 x (1+(1.043 - 1.057) x 3.35)
Anticipated Mash Efficiency = 0.7244 = 72.44% for a pre-boil SG of 1.057

(for all else remains constant, such as pre-boil volume, process, equipment, etc...)

 

[Silver_Is_Money]

Extending the above:

If (for a given pre-boil volume, which is to remain constant) hitting 76% mash efficiency at 1.043 PBSG requires 11 Lbs. of grist, then:

57/43 x 76/72.44 x 11 = 15.3 Lbs. of grist required to hit a PBSG of 1.057 at an efficiency of 72.44%.

 

[Silver_Is_Money]

If all constants remain constant, the above two posts math formulas can also be reliably applied to FG's and FV's (final volumes), but for some processes and/or equipment it may be a bit more difficult to get the final (meaning pre fermentation here) constants to remain sufficiently constant. That said, I've used it successfully for FG's without significant issues cropping up, but YMMV.