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OG Problems

I have had a problem hitting my Original Gravity lately. Before I moved to my new house I had brewed both Extract and All Grain and had no problem hitting my OG, however, since moving I have not been able to hit my OG’s. Today brewed an extract because my past six AG brews have failed to hit the mark. When I finished my extract brew today, my OG was supposed to be 1.046 and came out 1.035…this has been the typical difference in my AG brewing also. My temperatures are right and everything seems on point, what could be causing this difference? Is my stove top not getting hot enough? Is my hydrometer not calibrated properly? Do I just need to find another hobby(please say no)? Any help or advice would be very much appreciated.

Thanks-Mike Driscoll

The only way an extract batch can be off is if your water volume is off or the extract is not mixed completely.

Or, are you using a new hydrometer? Or the paper in the hydrometer get knocked out of adjustment?

… or you calculated the expected gravity incorrectly to begin with.

[quote=“Nighthawk”]The only way an extract batch can be off is if your water volume is off or the extract is not mixed completely.

Or, are you using a new hydrometer? Or the paper in the hydrometer get knocked out of adjustment?[/quote]

+1 What is your temp when your taking a reading?

I am going to try a new hydrometer. The calculations should be right because it was a kit from northern brewer. The temperature was 70 degrees, so I don’t think that was why the readibg was off. The hydrometer was the only thing I could think of besides thinking maybe it wasn’t boiling hard enough. Thanks for the help, very appreciated.

The strength of the boil will not make a difference. Unless you ending volume is not reached in the time you allocate for the boil.

A strong boil for 1 hour that reduces 6 gallons to 5 gallon will have the same results as a 2 hour simmer that reduces 6 gallons to 5 gallons.

New hydrometers can be off also. Test them in distilled water to see if they are off. You can paint some nail polish on to make it heavier. Or use a fine file to remove some glass to try and make it lighter.

Do you have a preference on the color? :wink:

I tested my hydrometer today, it was at 1.000 in 70 degree water. When i did my extract I started with 2.5 gallons of water per the kit instructions, which boiled down to 1.5. I then added 2 gallons to the carboy, per instructions, then added wort. And, again, per instructions topped off carboy to 5 gallons with 1.5 gallons of water. I am at a loss, figure it might be to much added, but followed the instructions and figured a kit purchased from NB would be a safe test kit since they have figured everything out for me…not sure what to do.

Your extract OG is off because the top-up water is not thoroughly mixed with the wort. This is very difficult to do at room temp and would require several minutes of stirring/shaking. Don’t even bother with OG measurements after top up, you can easily calculate the gravity with a known volume and amount of extract used.

How are you measuring out your finished wort volume and top up water? It’s best to have markings to the nearest quart, either with a graduated dip stick or markings on the container. Accuracy on this measurement directly affects your OG calculation, so being off by a quart on volume is a difference of 3 gravity points in 5 gallons.

@ nyakavt…I have gallon lines marked on my carboy, and use a pitcher with quart markings on it to add any water. Could you give me the formula for process you were talking about after adding the top off water? Thanks for the responses from everyone, nice to have support from others and njot feel as lost.

I just wouldn’t bother. If you know how much extract you are adding and how much wort volume you have, then you know the OG.

Alternately, you can do what I do, which is to measure the volume and gravity at the start of boil (chilling the wort before taking the gravity and accounting for the fact that the volume will shrink by 4% when cooled). Multiply the gravity times the volume and you know the total gravity points. Divide that by the final volume, including top-up water, and you have your OG.

[quote="miked4041Could you give me the formula for process you were talking about after adding the top off water?[/quote]
It’s just the standard way you figure OG by multiplying by pounds of extract used and dividing by # of gallons of wort. Extract yield is typically expressed in points per pound per gallon, which is ambiguous as stated so I prefer pointsgal/lb. Liquid is somewhere around 35 pg/lb, and dry is around 45 p*g/lb.

So if you make a batch of wort with 10 lbs of liquid extract, then top it up to 5 gallons, your OG is 35 p*gal/lb * 10 lb / 5 gal = 70 points, or 1.070.

To put what slothrob is saying into a formula: G1V1 = G2V2. So if you know the gravity and volume in the kettle with your concentrated boil, and the volume in the fermenter after top-up, you can figure out the gravity in the fermenter. It can be hard to get a concentrated boil gravity with big beers because of the limit of the hyrdrometer, but in that case you can get very close with an accurate weight measurement for the extract and volume measurement of the finished wort.

With that formula, my OG is correct. So there is no way to loose gravity points during the boil? As long as you have the proper water amount and extract amount you should be on no mater what…I take it? It works for me!! I also used some crushed grains in until the water reached 170 degrees, how would this factor in, is there a gravity for grains the same as there is for liquid and dry extract, and does it depend on the grain?

Right; you can’t evaporate sugar, only water.

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