Taking gravities

[eujamfh]

So on more then one occasion I have taken a gravity before boil and it ends up being within a point of my post boil gravity. The boil evaporated .75-1 gallon per five gallons so clearly it should be much lower…

When I take the gravity I give the pot a good stir and take it a couple times during ensuring thing are mixed up. The hydrometer is good - I have checked it with a spare…

My OG are general in the target range - its just the preboil ones that seem all over the place. Any idea what I am doing that could cause this?

 

[sparkshooter]

Are you taking both measurements at roughly the same temp?

 

[eujamfh]

temps different but used a temp adjusting calculator...

 

[Yooper]

temps different but used a temp adjusting calculator...

That's why. Even with calculators, readings taken over about 100 degrees are worthless.

Next time, chill your sample in a pitcher of ice water before taking the reading, making sure it's under 90 degrees, and then use a calculator to adjust for temperature. That should be pretty accurate.

 

[Croyzen]

Get a refractometer. Brew day is enough work already. Pour a spoonful and get an instant reading. Just make sure you have a temp correcting model. Amazon. 30 bucks. I'm way too impatient to deal with pulling and chilling samples. If you want you don't need the hydro at all on brew day. Northern Brewer has a calculator that will calculate OG by taking a brix reading AND a hydro reading on bottling/keg day. I've checked it for accuracy and it works. I still want the OG on brew day.

 

[eujamfh]

Ugh! Indeed the samples were in the 130-140s taken from the sparge. Yopper - that hits the nail on the head since my OG are typically spot on (taken in the 70s) given any recipe (usually running about 75% efficiency).

So - that is the choice that I have…chill the sample or get a refractometer…another toy or use what I have….

Thanks again - you confirmed what I suspected but was still not sure about!

 

[gwapogorilla]

I dunno guys. I use beersmith hydrometer tool when I check my samples. I use a hydrometer and a digital thermometer at the same time. When I enter it into the tool in beersmith, I am always within 2 points of what beersmith says I should be.

What calculator and type of thermometer are you using?

 

[pvault98]

+1 on getting a refractometer. I use a disposable pipet and check my gravity throughout the sparge and boil. I am able to make adjustments at any point in the process by taking a tiny sample of wort and reading it instantly. My pre-boil gravity and OG are always dead on or within 1 point of what I expect them to be. You can also use the refractometer when making your starters to make sure the wort is within the range. It is money well spent and saves you the hassle of pulling extra wort, chilling, checking the temp, etc. 5 seconds worth of work and you have your gravity and can go back to all of the other tasks.

 

[Brewmex41]

I agree, refractometers can be inexpensive and can save you headaches like this. I picked one up on amazon, and with an order over like 35 i think shipping is free. Ordered on a thursday and came that saturday from California to Vancouver, Wa.

I figured since the post fermentation readings were somewhat useless with a refractometer that I would be wasting time and money getting one. But i found that it is worth it.

 

[cjgenever]

$27 Chinese knockoff refractometer from eBay. Free shipping. I got the heavy duty one from a us seller. It's spot on and incredibly useful. The parts are built well.

Sent from my SCH-R970 using Home Brew mobile app

 

[millsbrew]

Another refractometer convert here. After many brews pulling samples and waiting for it to chill only to worry about missed gravities, I spent $30 on a ATC model. There are a ton of calculators to help with post-fermentation readings. Another point is the post-fermentation readings will be saving a whole beer using the refractometer. More beer to drink is always good to me.


Sent from my iPhone using Home Brew

 

[aslander]

I thought post fermentation readings with a refractometer were supposedly off and you had to adjust? I don't own one but remember reading something like that

 

[pvault98]

I thought post fermentation readings with a refractometer were supposedly off and you had to adjust? I don't own one but remember reading something like that

They are and have to be adjusted as refractometers measure the light refraction of sugar in water and the alcohol affects how the light is refracted so once alcohol is present the calibration is no longer correct for that solution. Also from my experience the conversion doesn't work well once gravity starts to get below 1.010 and the readings are just too low. For example I had a beer that was about 1.008 on a hydrometer however the corrected refractometer reading was something like 1.001.

 

[aslander]

Yeah, so refractometer easiest for OG and hydrometer easiest for FG it sounds like

 

[GotPushrods]

Yeah, so refractometer easiest for OG and hydrometer easiest for FG it sounds like

If you know the OG, getting the FG is still much simpler with a refractometer Add a few DROPS, type in your uncorrected FG (i.e. 1035) to an online calculator along with your OG, and it spits out your actual FG, say 1.012.

After taking dozens of measurements there is a way to determine if your refractometer needs a slight correction factor. But most are very accurate out of the box, and we're talking a point, maybe 2, anyway.