New (larger) brewkettle contributing to lower OGs?

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saxman1036

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I recently upgraded my brewkettle from a plain stainless steel 5 gal pot to an 8-gallon polarware. It makes brewing a lot easier, however my stove is having a tougher time getting 6 gallons to a boil than I expected. In fact, unless I leave the lid on for at least 5 minutes (bad idea), I can never reach nor maintain much more than a strong simmer. I didn't think much of this until I also noticed that my switch to a larger pot also correlated with consistently under-shooting my target OG... usually by 5-10 points (I've replaced my hydrometer, so that's not an issue). So my questions...

1) will the inability to maintain a strong boil for extended time reduce the amount of sugars that dissolve in the wort?

2) can extending my "boil" time to 70 or 80 minutes help to mitigate any negative side effects of not coming to a true boil for 60 minutes?

3) is it possible for sugars to coagulate with other solids during the cold break, such that if draining from a spigot they get left behind in the brewkettle?

I'm already taking steps to address these two of these (I just bought an outdoor propane burner for easier boiling, and I plan to strain the wort just to see if that gives me a little bit of an OG bump), but I'm interested if any of you out there have any thoughts on how not maintaining a boil can affect gravity readings.
Thanks!
 
1) will the inability to maintain a strong boil for extended time reduce the amount of sugars that dissolve in the wort? Check your post-boil volume, if it's higher than you typically get than that is the issue.

2) can extending my "boil" time to 70 or 80 minutes help to mitigate any negative side effects of not coming to a true boil for 60 minutes? You need to get a boil going to push DMS precursors out of the wort if you are doing All-Grain brewing, maybe look in to a heatstick for helping out the stove? Boiling for longer will however help your evaporation and get you back down to your original volume thus increasing your OG.

3) is it possible for sugars to coagulate with other solids during the cold break, such that if draining from a spigot they get left behind in the brewkettle? Nope, not unless you didn't mix them well enough to dissolve. They should be dissolved in to the liquid wort by the end of a 60minute boil.
 
I think you really just need to invest in a propane burner and move outside. Home Depot/Lowes even typically discounts their burners right after Christmas, as they consider them a seasonal item. A decent burner will only set you back about $30-40. You can probably even find one used on Craigslist for more like $10-15.
 
wyzazz said:
1) will the inability to maintain a strong boil for extended time reduce the amount of sugars that dissolve in the wort? Check your post-boil volume, if it's higher than you typically get than that is the issue.

2) can extending my "boil" time to 70 or 80 minutes help to mitigate any negative side effects of not coming to a true boil for 60 minutes? You need to get a boil going to push DMS precursors out of the wort if you are doing All-Grain brewing, maybe look in to a heatstick for helping out the stove? Boiling for longer will however help your evaporation and get you back down to your original volume thus increasing your OG.

3) is it possible for sugars to coagulate with other solids during the cold break, such that if draining from a spigot they get left behind in the brewkettle? Nope, not unless you didn't mix them well enough to dissolve. They should be dissolved in to the liquid wort by the end of a 60minute boil.

Thanks for the response! I have a few follow-up questions...

1) does the post boil volume matter if it only means that I supplement with less water added to the primary? I would think that the same amount of sugar ends up in the carboy, so it shouldn't matter if the extra water is added at the end when topping off or if it's in the kettle during the "boil".

3) What about late sugar additions? Typically corn sugar or dme gets added pretty late... I make an effort to stir them in well, but could they not have enough time to dissolve?
 
Sure thing, let me give these a shot.

1) does the post boil volume matter if it only means that I supplement with less water added to the primary? I would think that the same amount of sugar ends up in the carboy, so it shouldn't matter if the extra water is added at the end when topping off or if it's in the kettle during the "boil". If you are topping up after the boil then it should not matter.

3) What about late sugar additions? Typically corn sugar or dme gets added pretty late... I make an effort to stir them in well, but could they not have enough time to dissolve? Late sugar additions shouldn't matter, however topping up does. If you're not mixing your wort up with something akin to a paint mixer on a drill for around 5 minutes after topping up, than you are likely not getting a proper OG reading. If you're making a kit then they are usually pretty spot on as far as OG is concerned, if you aren't you can use some simple math or brewing software to calculate your OG. As long as your finishing volume is correct and you added the correct amount of sugar (DME/LME/ETC...), things should match up.
 
I feel as though I aerate the fairly well, but I will admit I don't do it for 5 minutes. What methods do you use for aeration? That seems as though it may be the simplest solution to my problems.

On a related note (at least to earlier comments of mine), the propane burner arrived today! Super pumped to put that to use.
 
How do you aerate?

I fill up my fermenters (plastic buckets), then dump into another sanitized bucket, and then back into the fermetor- takes about 15 seconds.


I am sure that others have different methods but this has worked for me.
 
While you can certainly use a Mix-Stir for aerating and mixing your top up water after a partial boil, if your pot is big enough and you now have a propane burner I would start doing full boils.
 
Keep in mind that the gravity is not simply a measure of how much sugar you have but what ratio os sugar to water. Because of this if all else is the same but you have a different final volume you will have a different gravity. A major part of the rolling boil is getting rid of water to concentrate the same amount of sugar into a smaller amount of water. The thing about topping off is that if you boil off 2 gallons then add back in 2 gallons you have just taken your gravity back to it's preboil level.
To see this mathematically drop the "1.0" off your gravity multiply that by your initial gravity. Divide this amount by your new volume and you have your new gravity.

Example: 1.030 wort of five gallons boiled down to four gallons would be:

(5x30)/4= 4375, so the new gravity is 1.043.

1.040 wort of four gallons topped off to five gallons would be:

(4x40)/5= 32, so the new gravity is 1.032.

You really NEED a burner to get a strong boil.
 
It sounds like you are doing partial boil extract recipes. The boil has nothing to do with sugar conversion and you cannot change the amount of sugar in the wort, that is determined by the amount of extract you are using.

If your OG is lower there are three possible reaons; 1) you didn't use the amount of extract/sugar the recipe called for or 2) your volume is different from what the recipe called for, or 3) your water addition is not thoroughly mixed if 1 and 2 are correct.

It would help if we knew what volume you were boiling, what your post boil volume was, and what volume you are topping off to.
 
That is supposed to say, "multiply that by your initial volume," not "by your initial gravity."
 
I did a few calculations using the formula that cluckk suggested...
Suppose I start with 6 gallons of wort, pre-boil, at 1.050. If I boil down to various volumes, here's what I would be looking at *before* I top off to 5.5 gallons in my carboy:

Boiled down to...
5.5 - 1.055
5 - 1.060
4.5 - 1.067
4 - 1.075

If I plan to top all of these off to 5.5 gallons for primary fermentation, I would need to add various amounts of water to do this. The results are interesting...

5.5 (no extra water needed) - 1.055 OG
5.0 (.5 gallon added) - 1.055 OG
4.5 (1 gallon added) - 1.055 OG
4.0 (1.5 gallons added) - 1.055 OG

What this suggests to me is that it doesn't matter how much you boil, as the volume is restored to a full 5.5 gallons for primary fermentation anyway. The amount of sugar hasn't changed, and neither (in the end) has the water. So I'm still confused on how boil-volume affects the OG.

As for my other concern , in reading some other comments, perhaps I'm not aerating my wort well enough. I'm still able-bodied enough (and cheap enough) to be content rocking my carboy back and forth for my aeration. I have a number of other methods used in other threads, including research abstracts on the matter, and many suggest that rocking is sufficient if done for only 5 minutes. Maybe I just need to do this for longer...?
 
The amount of sugar hasn't changed, and neither (in the end) has the water. So I'm still confused on how boil-volume affects the OG.

OG is the gravity of your wort going into the fermenter. Changes through boiling and topping off are what gets you to that OG. What you are measuring is the amount of sugar dissolved in a volume of water. If you change either the water or the amount of sugar you change the gravity. Boiling does many things--sanitizing, blowing off unwanted compounds, isomerizing hops, etc. With gravity, boiling changes the ratio of water to sugar. To raise final gravity you can either increase the amount of sugar through mash efficiency or reduce the amount of water by boiling down. For example:

If I brew a batch in which I want an OG of 1.050 in a 5.5 gallon batch, and I start with boiling 7 gallons from my MLT, then I need my preboil gravity to be 1.039. However, what if I miss this number way low? If my efficiency is off in my mash and I only get 1.025 in that 7 gallons then with the same amount of boiling I will only achieve an OG 1.031 (into fermenter). This will be a very weak beer and way off my target. However if I boil it down to 3.5 gallons my gravity of 1.050 is hit and I would then cool and ferment this amount. I would end up with much less beer, but it would be at my gravity. (I would have traded volume for gravity) If I insist on having a 5.5 gallon batch then I must accept the weaker beer (unless I add sugar in one form or another).

Note: you would have to boil much longer which would caramelize more sugars (making it sweeter) and would also require you to alter your hop schedule.

The only other option, after pulling off from the MLT and starting the boil would be to add sugar into the kettle--such as Brewer's Sugar, honey, extract, etc. Be careful about these because they will thin out a beer.

I had one batch come in very low--it was during a parti-gyle experiment--so I added Brewer's sugar to the kettle and raised the OG from 1.023 to 1.030. This will of course produce a thinner beer, but I wanted the gravity.

The issue is the topping off. If your gravity is not high enough you can either remove water and have less of a stronger beer, add sugar to make the larger beer stronger, or continue to top off to get you target volume of a weaker beer.

If you have the kettle and MLT volume for a full batch and a cooker that will boil 7 to 8 gallons reasonably, then give up the topping off and instead boil the full batch.
 
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