Gravity Issue

So, I have had the same issue for the last three brews that I have never had before. I have over 50 brews under my belt, and I have to say this issue has me perplexed. I brewed yesterday and after transfer from mash tun and after sparge, my pre boil gravity was 1.043 (recipe called for 1.040). After a 60 minute boil and chilling my wart, I took my OG gravity reading. ONLY 1.044. The recipe calls for and OG of 1.055. I used a refractometer and my hydrometer and got the same reading. What could possibly cause this?

What did the beer taste like?

Assuming your preboil SG was correct, then the only way I can see gaining only 1 gravity point after a 60 minute boil is if you only had about a 3-4oz. water loss due to the boil. So something has to be off. Could your chiller have a leak that’s adding water back to your kettle?

Wort tasted like wort. It is a recipe that I have brewed a lot. I checked the chiller and no leaks. Lost 2 gallons in the boil. This was a 10 gallon batch

You double checked the OG did you double check the BG ? Did you correct for temp? Just throwing stuff out there. What were your gravities the other times you made that beer. That is confusing.

I double checked the Pre Boil and triple checked the OG. The other brews where I had the same problem were all within this range. OG only went up .01 after an hour boil. I had to boil them and extra 45 min to get to my target OG. This has been so frustrating. I literally cannot think of why this is happening. Could weather be a factor. I never had this issue in warmer weather. Am i Just stretching with this theory?

Are you taking your preboil gravity reading with refractometer or hydrometer? are you chilling the samples? I find that my preboil gravity readings when using my refractometer were all over the place till I started taking a larger sample and cooling it quickly, then taking the reading. You could be getting evaporation on your preboil reading causing the reading to be high. There is no way that your boiling for 1hr and only gaining 1 point.

I took the pre boil gravity with the refractometer. I used the eye dropper to extract the wort, cooled it in an ice bath, then took the reading. Same thing with the OG plus I used my hydrometer. Same readings with both the refractometer and the hydrometer.

Have you changed water sources? I’m not a chemist but could something be converting the sugars to something more soluble?

Maybe your wort is not mixed well after the sparge and you’re not getting a true pre-boil gravity? I think I’ve had that happen a couple of times because I had similar differences between pre-boil and OG. I’m usually on or over target OG though.

Have you always done 10 gal batches or are you just scaling up and seeing this issue?

What were your pre-boil and post-boil volumes?

The water source is the same. I just use either the tap water or water out of the hose if it is warm enough (same source). Let me clarify one thing. Out of the three batches, two were 5 gallon batches. I brewed these inside on my kitchen stove. I had a good rolling boil on both of them. I figured that the hood was allowing the steam to get back into the wort, and thus I was not losing enough volume. I ended up having to re-boil the wort for another 30 min to an hour. The last batch I did with a friend. I shared a recipe with him and so we used his 10 gallon system. It was my first time brewing 10 gallons but not his. I think the pre-boil gravity was correct as i triple checked it. He took the OG when I was not there and upon further discussion with him, I do not think he mixed up the wort well enough before he took the reading. What confuses me the most is how we both had this problem on two separate brewing rigs.

On the 10 gallon batch, the pre boil volume was 14 gallons, and the post boil we got just over 10 gallons.

You had 4 gallons of boil off in an hour? That seems a bit high. Or was this after additional boiling?

This calculator here should tell you exactly how much you will need to boil off to achieve your target gravity. ... alculator/

I always use this after i check my pre-boil gravity to make sure im going to be anywhere near my target gravity with a 60 minute boil and adjust if i am a bit low on gravity. It’s obviously better to boil more before adding the hops to prevent excess bittering.

+1 to Dannyboy. I usually let my wort come to a boil for a few minutes prior to checking my “pre-boil” gravity. I’ve consistently hit somewhere near the predicted “pre-boil” gravity since I started doing this. Prior to that it would be all over the place.


If you have friends who brew take your hydrometer and refractometer over to their house on a brew day or borrow theirs for your brew day. I know the odds that both of yours are having the same problem at the same time is remote, but hell some people win the lotto and those odds are insane.