Low Original Gravity readings

[Bw1985]

Hi all,

I noticed that the last couple batches of beer I made had lower than expected OG readings. Not sure what’s going on, could this be due to mash water temp? Too much water in the mash?

I still ended up with great tasting 5% (or above) beers but was aiming for closer to 6-7%. For example, my latest West Coast Pale had an OG of 1.052 but I was aiming for above 1.060. The beer seems to be fermenting as expected and there was no lag or anything after pitching yeast.

Had around 12.5lbs of grain, 0.5lbs dextrose, 5 gallons of mash water at 170f for 60mins (held at 162 as I wanted), then sparge with 3 gallons at 175.

Boiled for 60mins, cooled and transferred to fermentor. Pitched yeast and took my sample. Tasted and looked great!

Any advice or pointers would be helpful. I can provide more info if needed.

Thanks!

 

[bracconiere]

5 gallons of mash water at 170f for 60mins (held at 162 as I wanted), then sparge with 3 gallons at 175.

too hot....you want your mash at ~150f, and your sparge wtaer around 168f......and i'd also say you used too much strike water....be better off saving that volume for a better sparge/rinse.....

 

[DVCNick]

A couple thoughts...
It is probably ok but that mash is a little thin, most people recommend 1.25-1.5 qt per pound.
The dextrose would normally be added late in the boil... not sure what the effect would be, but want to make sure it isn't going in the mash.
162 is quite high... 152 is usually more like the center of the recommended range and tweak slightly from there if so inclined.

 

[Bw1985]

Thanks for the reply. Odd about the temp being too hot because the recipe called for just above 160 on mash? I used 170 for strike because the grain brought it down to 160ish. How much strike water would be better?

 

[Bw1985]

And yes, I used the dextrose late in the boil to try to produce a higher abv.

 

[AzOr]

Agree with others that mash temp may be high.
Another thing- don’t be afraid to throw in some dme to adjust og while you’re getting used to your system.
I did that for a few batches while I was switching from extract to all grain brewing.
Dme is useful to have around for yeast starters anyway.

 

[bracconiere]

recipe called for just above 160 on mash?

sure that wasn't a strike temp? i mash-in at 162f, with 20lb's of 70-80f malt.....get about 150f after mixing it in.....and 7 gallons of water....for a 10 gallon batch, and sparge with 10 gallons....

 

[Bw1985]

sure that wasn't a strike temp? i mash-in at 162f, with 20lb's of 70-80f malt.....get about 150f after mixing it in.....and 7 gallons of water....for a 10 gallon batch, and sparge with 10 gallons....

It’s entirely possible I screwed up and used strike temp value. I used a water calculator before that recommended 9 gals of water (around 4.5 each for strike and sparge) and still had the low OG.

This is also the first few times I’ve used RO water and added gypsum and calcium carbonate as well. Could that be a factor? Previously I used tap water and never had this issue.

 

[DVCNick]

I'm assuming this is a five gallon batch? What was your target preboil volume, did you hit it, and what was your post boil volume?

 

[bracconiere]

i'm scared of water calculators.....

tried using them once, had me adding so much gypsum, my beer was so acidic, it wouldn't ferment......

edit: didn't realize it until i bought a ph meter.....

 

[Bw1985]

To be honest, those aren’t factors I was worrying about. I haven’t come up with a good way to measure those (advice appreciated). I’ve been on more of a learning path trying to make beer that didn’t turn out like crap! (Had 2 failed batches last summer, this year I have had good results). Still a newbie to all of this, so apologies for my ignorance on technique.

 

[marc1]

To be honest, those aren’t factors I was worrying about. I haven’t come up with a good way to measure those (advice appreciated). I’ve been on more of a learning path trying to make beer that didn’t turn out like crap! (Had 2 failed batches last summer, this year I have had good results). Still a newbie to all of this, so apologies for my ignorance on technique.

Wait, does this mean that you don't know what your volumes are before and after the boil? If your volume is higher at the end than calculated for, then it's not an efficiency issue, it's a dilution issue.

 

[Bw1985]

Wait, does this mean that you don't know what your volumes are before and after the boil? If your volume is higher at the end than calculated for, then it's not an efficiency issue, it's a dilution issue.

Unfortunately the answer to that is yes. I only learned to brew last summer from a friend. So that wasn’t something he taught me. I brewed several ale recipes with great results. Never any problems achieving my OG or FG. With these newer recipes I agree, I think it is dilution. Should I mark all my brew pots and fermentors with measurement marks? They don’t have any lines to indicate volume. I figured they usually “looked about right”.

 

[VikeMan]

Should I mark all my brew pots and fermentors with measurement marks?

Probably. You will never know your true mash/brewhouse efficiencies, and probably won't ever get your process dialed in, if you can't measure volumes.

Never any problems achieving my OG or FG. With these newer recipes I agree, I think it is dilution.

If you use brewing software, you will never be at the mercy of someone else's recipe (and the assumptions those recipes make about your brewhouse). You can make any recipe fit your equipment and process.

 

[marc1]

Unfortunately the answer to that is yes. I only learned to brew last summer from a friend. So that wasn’t something he taught me. I brewed several ale recipes with great results. Never any problems achieving my OG or FG. With these newer recipes I agree, I think it is dilution. Should I mark all my brew pots and fermentors with measurement marks? They don’t have any lines to indicate volume. I figured they usually “looked about right”.

Now we're getting somewhere in the troubleshooting! This might not be the only cause, but it will help you be more consistent with your brews. Once you know your volumes, you can start filling in all the missing pieces to dial in your process. Then you can tweak recipes (or come up with your own!) so that they come out as expected on your system.
I have long handled wooden spoons with notches cut into the handle for volume. The volume is going to be a little higher when hot so don't be surprised if it goes down when you chill.

 

[Bw1985]

Now we're getting somewhere in the troubleshooting! This might not be the only cause, but it will help you be more consistent with your brews. Once you know your volumes, you can start filling in all the missing pieces to dial in your process. Then you can tweak recipes (or come up with your own!) so that they come out as expected on your system.
I have long handled wooden spoons with notches cut into the handle for volume. The volume is going to be a little higher when hot so don't be surprised if it goes down when you chill.

So I brewed again today, and am still experiencing the low OG! This is so weird, I was super careful with all of my measurements. I can break down all of my numbers to see if this can prove anything.

13lbs of grain, 4 gallons mash water at 160 (held perfectly at 150 for 60 mins). Drained mash tun (noticed grain soaked up a lot of water, not tons in my boiling pot). Continued with sparge water (another 4 gallons this time at 170). Added it all at once to grain, noticed the wort during sparge looked a little thin). Ended up with 6.5 gal pre-boil. Pre-boil gravity was low, (around 1.032?). Started my boil, took a gravity reading after 60mins and noticed the OG was still too low (still below 1.040). Boiled for another 30 mins, chilled my wort and ended up with slightly below 5 gal. OG reading with corrections was 1.043. I was shooting for 1.056, and have no idea where I went wrong. At least the longer boil saved the beer and I lost volume, but won't be a 3% ale, ha!

Any advice or feedback is appreciated. I know the beer will likely taste good and ferment, but still disappointed it will be lower abv than I hoped..

 

[bracconiere]

Drained mash tun (noticed grain soaked up a lot of water, not tons in my boiling pot). Continued with sparge water (another 4 gallons this time at 170). Added it all at once to grain, noticed the wort during sparge looked a little thin). Ended up with 6.5 gal pre-boil.

back before i learned to sparge slowly i used to get 62% effec.....i'd just open the valve full bore and dump water onto the grain.....then i learned i was supposed to just crack the valve a bit and let it drain slowly while topping it up with fresh water.....

 

[Bw1985]

back before i learned to sparge slowly i used to get 62% effec.....i'd just open the valve full bore and dump water onto the grain.....then i learned i was supposed to just crack the valve a bit and let it drain slowly while topping it up with fresh water.....

Would that be the proper approach? I thought I had tried that before but still ended up with low gravity. I fully drained my mash water, closed the value, then dumped my batch of sparge water in and opened the valve to drain to get my pre-boil volume of 6.5gal.

 

[bracconiere]

Would that be the proper approach? I thought I had tried that before but still ended up with low gravity. I fully drained my mash water, closed the value, then dumped my batch of sparge water in and opened the valve to drain to get my pre-boil volume of 6.5gal.

sounds like what i've heard of a batch sparge...how long did you let your second running sit in the tun to dissolve the sugar? sugar is water soluble, but, still needs some time to get to know each other....a batch sparger would have to chime in on that....

i'm no pro brewer or anything, just amature...that got help from forum like this when i was getting 62%, and they helpped me get it to 83%, and now 90%.....lol i just shake malt at water now, and get 9% ABV beer!

 

[bracconiere]

pre-boil volume of 6.5gal.

i haven't brewed a 5 gallon batch in a LONG time, but that also seems low? if i remember, when i brewed 5 gallon batches, i'd get like 7-7.5g's.....or to the brim of a turkey frying pot.....

 

[Bw1985]

sounds like what i've heard of a batch sparge...how long did you let your second running sit in the tun to dissolve the sugar? sugar is water soluble, but, still needs some time to get to know each other....a batch sparger would have to chime in on that....

i'm no pro brewer or anything, just amature...that got help from forum like this when i was getting 62%, and they helpped me get it to 83%, and now 90%.....lol i just shake malt at water now, and get 9% ABV beer!

Haha! That is what my goal is at this point...here's hoping. To be honest I didn't give the batch sparge that much time...perhaps that's where I went wrong. Hopefully a fellow batch sparger will chime in...

 

[Bw1985]

i haven't brewed a 5 gallon batch in a LONG time, but that also seems low? if i remember, when i brewed 5 gallon batches, i'd get like 7-7.5g's.....or to the brim of a turkey frying pot.....

I don't think my pot would hold much more than 7gals... I was too worried about dillution and low gravity so I went with the 6.5 gal.

 

[bracconiere]

https://www.homebrewtalk.com/threads/maximizing-efficiency-when-batch-sparging.77125/

 

[bracconiere]

I was too worried about dillution and low gravity so I went with the 6.5 gal.

dillution is a good thing for a sparge, if you boil the water off.....the more you can rinse the grain the better, that's why people brewing BIG beers get crappy effec, can't rinse enough, or they'd have to boil for 5 hours to get good effec.....


i posted a link to something you might get some use out of.....just scanned it myself....

 

[Holden Caulfield]

A couple of thoughts...

1. At 160, the alpha amylase should still convert all of the starches. However, the fermentability of your wort will be low so you will end up with a high finished gravity. See chart below from BYO. That said, the mash temp, if accurate, is probably not the reason for your low OG.
2. 13 pounds of grain for a 5 gallon batch should provide adequate fermentables to hit your your OG. 8 gallons of water should be adequate and will leave you with about 6 gallons in the kettle. This suggests about a 72% efficiency which is even low for BIAB. Perhaps during your second batch sparge you are not mixing the grains first, and then channeling all the added sparge water straight through to the mashtun without extracting remaining fermentables?
3. Is your grain bill high in adjuncts, as the diastatic power of your mash may not be high enough to convert all the starches to sugars reducing your efficiency and lowering your OG?

 

[Tobor_8thMan]

Thanks for the reply. Odd about the temp being too hot because the recipe called for just above 160 on mash? I used 170 for strike because the grain brought it down to 160ish. How much strike water would be better?

I believe the 160F meant the mash in temp figuring once the grains were stired into the 160F the temp would settle on 150F to 152F. In other words, 160F is too high for the whole mash (be it 60 minutes, 90 minutes, etc) time.

 

[bracconiere]

A couple of thoughts...

1. At 160, the alpha amylase should still convert all of the starches. However, the fermentability of your wort will be low so you will end up with a high finished gravity. See chart below from BYO. That said, the mash temp, if accurate, is probably not the reason for your low OG.
2. 13 pounds of grain for a 5 gallon batch should provide adequate fermentables to hit your your OG. 8 gallons of water should be adequate and will leave you with about 6 gallons in the kettle. This suggests about a 72% efficiency which is even low for BIAB. Perhaps during your second batch sparge you are not mixing the grains first, and then channeling all the added sparge water straight through to the mashtun without extracting remaining fermentables?
3. Is your grain bill high in adjuncts, as the diastatic power of your mash may not be high enough to convert all the starches to sugars reducing your efficiency and lowering your OG?

View attachment 694076

he tried again and mashed at 150f......but thanks for the picture! i haven't actually seen one with the extract yield on it, that i remember....that slight increase could explain why i go from 83% effec, to 88-90% with a second 162f step.......


(off-topic, but i'm still trying to get someone else to try it that doesn't add gluco to everything! to see how it affects fermentability)

 

[Willee]

Brew for flavor ... you can always add everclear to raise the ABV.
If that is not desirable then add some DME to your boil.

 

[Gnomebrewer]

So I brewed again today, and am still experiencing the low OG! This is so weird, I was super careful with all of my measurements. I can break down all of my numbers to see if this can prove anything.

13lbs of grain, 4 gallons mash water at 160 (held perfectly at 150 for 60 mins). Drained mash tun (noticed grain soaked up a lot of water, not tons in my boiling pot). Continued with sparge water (another 4 gallons this time at 170). Added it all at once to grain, noticed the wort during sparge looked a little thin). Ended up with 6.5 gal pre-boil. Pre-boil gravity was low, (around 1.032?). Started my boil, took a gravity reading after 60mins and noticed the OG was still too low (still below 1.040). Boiled for another 30 mins, chilled my wort and ended up with slightly below 5 gal. OG reading with corrections was 1.043. I was shooting for 1.056, and have no idea where I went wrong. At least the longer boil saved the beer and I lost volume, but won't be a 3% ale, ha!

Any advice or feedback is appreciated. I know the beer will likely taste good and ferment, but still disappointed it will be lower abv than I hoped..

Your problem is probably either mash conversion or lauter (sparge) efficiency. To find out which, you need to measure. At the end of your mash, measure the gravity of the wort. Use this spreadsheet http://braukaiser.com/documents/efficiency_calculator.xls to work out your conversion efficiency. It should be over 90%, preferably over 95%. If it's not, you need to mash longer or crush finer (or maybe address water issues). Unfortunately most recipes say 'mash for 60 minutes'. This is poor advice. A BIAB'er with a very fine crush can get full conversion in much less than 60 minutes. A coarse HERMS crush might take 90 minutes. A poor crush might take longer still. The point is that the mash should run for as long as it needs to. Adding a rest at about 162F helps speed up conversion.

If conversion efficiency isn't the issue, it's probably lauter efficiency. Measure the gravity in the boil kettle and multiply it by the volume in the boil kettle, then divide by the total potential gravity points. There are also lots of online calculators that will work it out for you. For a single sparge beer in the 1.050 to 1.060 range, this should be somewhere around 70 to 80% at a rough guess. If it's much lower than that, you must be leaving liquid behind when you drain the mash tun.

If efficiency is good into the boil kettle, your problem must be lost wort after boilling.

Hope this helps.

 

[MikeCo]

I’ve never batched sparged, but some quick research on it shows that usually two water additions are recommended, each with some waiting period before draining the tun to allow the sugars to dissolve. There’s always a vorlauf step as well for clarification but I don’t know if that has any effect on efficiency. Generally the total sparge water is more than the mash water.

 

[VikeMan]

Generally the total sparge water is more than the mash water.

That would generally be true with double batch sparges. In any case, the most efficient batch sparges are where each running, i.e. first (pre-sparge) running, second running, and third running (if applicable) has the same runoff volume as the others.

 

[Bw1985]

A couple of thoughts...

1. At 160, the alpha amylase should still convert all of the starches. However, the fermentability of your wort will be low so you will end up with a high finished gravity. See chart below from BYO. That said, the mash temp, if accurate, is probably not the reason for your low OG.
2. 13 pounds of grain for a 5 gallon batch should provide adequate fermentables to hit your your OG. 8 gallons of water should be adequate and will leave you with about 6 gallons in the kettle. This suggests about a 72% efficiency which is even low for BIAB. Perhaps during your second batch sparge you are not mixing the grains first, and then channeling all the added sparge water straight through to the mashtun without extracting remaining fermentables?
3. Is your grain bill high in adjuncts, as the diastatic power of your mash may not be high enough to convert all the starches to sugars reducing your efficiency and lowering your OG?

View attachment 694076

Wow thanks for all the responses, I truly appreciate it. I think #2 sounds like one of my issues. I think I just dumped all my sparge water in and didn’t even let it soak. So I basically just ran hot water into my boil pot and diluted the heck out of it!

In regards to #3, my grain bill was 6lbs of 2 row, 6lbs of wheat malt, 1/2lb of Munich, 1/2lb of carafoam.

I’ve never batched sparged, but some quick research on it shows that usually two water additions are recommended, each with some waiting period before draining the tun to allow the sugars to dissolve. There’s always a vorlauf step as well for clarification but I don’t know if that has any effect on efficiency. Generally the total sparge water is more than the mash water.

So, if I sparge with 4gal, should I split it in 2gal sparges at 170f and let them sit for a good 20 mins each? I don’t think my mash is problematic, pH looked healthy and it held solidly at 150.5 for an hour.

I never had issues when I used to batch sparge at closer to 180f, but I heard over 175 can strip too many bitter flavors off the grains. Is there any issue going hotter, or should I stay in 170f range?

 

[Bw1985]

Your problem is probably either mash conversion or lauter (sparge) efficiency. To find out which, you need to measure. At the end of your mash, measure the gravity of the wort. Use this spreadsheet http://braukaiser.com/documents/efficiency_calculator.xls to work out your conversion efficiency. It should be over 90%, preferably over 95%. If it's not, you need to mash longer or crush finer (or maybe address water issues). Unfortunately most recipes say 'mash for 60 minutes'. This is poor advice. A BIAB'er with a very fine crush can get full conversion in much less than 60 minutes. A coarse HERMS crush might take 90 minutes. A poor crush might take longer still. The point is that the mash should run for as long as it needs to. Adding a rest at about 162F helps speed up conversion.

If conversion efficiency isn't the issue, it's probably lauter efficiency. Measure the gravity in the boil kettle and multiply it by the volume in the boil kettle, then divide by the total potential gravity points. There are also lots of online calculators that will work it out for you. For a single sparge beer in the 1.050 to 1.060 range, this should be somewhere around 70 to 80% at a rough guess. If it's much lower than that, you must be leaving liquid behind when you drain the mash tun.

If efficiency is good into the boil kettle, your problem must be lost wort after boilling.

Hope this helps.

Based on this equation I think my efficiency is in the 63% range. 1.030 gravity with 6.5gal in the boil pot. Was aiming for 1.056.

 

[bracconiere]

Based on this equation I think my efficiency is in the 63% range. 1.030 gravity with 6.5gal in the boil pot. Was aiming for 1.056.

that would be a pre-boil gravity.....

 

[Holden Caulfield]

So, if I sparge with 4gal, should I split it in 2gal sparges at 170f and let them sit for a good 20 mins each? I don’t think my mash is problematic, pH looked healthy and it held solidly at 150.5 for an hour.

I never had issues when I used to batch sparge at closer to 180f, but I heard over 175 can strip too many bitter flavors off the grains. Is there any issue going hotter, or should I stay in 170f range?

Regarding batch sparging with 4 gals - you can do a single (no split) or double (split) batch sparge. You will get a little bit better efficiency with the double but less than you may think and may not be worth the extra time. Also, your PH climbs as your wort concentration declines so your risk of tannin extraction goes up with a double batch sparge. A few less efficiency % points can easily be made up with just a little bit more grain. In other words, spending a couple of $s more may lead to better beer.

Regarding batch sparging at 180 - not necessary, and potentially detrimental to your wort. 170 is more than adequate to rinse your grains. Above 170 you risk extracting tannins. Interestingly, research has demonstrated that most tannin extraction is due to high PH rather than temperature at sparge temperatures, that said, better safe than sorry.

Agree it's not your mash temperature.

Additional hypotheses to evaluate...

1. As mentioned in another response - your grains may not have been crushed enough.
2. Wheat malt (~50% of your grain bill) has a high PH relative to other base malts, and you have no roasted or crystal malts so unless you are treating your water, you probably have a high PH which will affect conversion and efficiency. Although probably not by the amount you are experiencing. How do you know the PH looked healthy? Even with 0 alkalinity, I would expect your PH to be in the 5.7 to 5.8 range, depending on how low your 2-row ph is, as it can vary quite a bit depending on maltster and origin.
3. Was the wheat malt actually wheat malt or un-malted wheat. Mistakes happen when filling orders. If un-malted wheat, the diastatic power of your mash would be around 50 which may be borderline for converting all that the un-malted wheat in an hour

Last, if you have access to Excel, below is a link to the program I wrote to build recipes. It is designed around how a homebrewer makes beer. It may look complicated but if you start with Brew System Inputs it will help you to think think about how your systems affects final batch size and OG. After this, build a recipe by first creating your "Beer vision" and then build the recipe in the "Grain-Hops Plan". The Execution worksheet will have all the information for brew day. Ignore the other worksheet as they are for building step and decoction mashes and water chemistry. By going through this process you will learn pretty much all there is to know about making good beer. I am happy to answer any questions.

https://www.dropbox.com/s/pc1vjpqre9dzjhz/Buildabeer v6.2 - DB.xlsm?dl=0
Regards,

 

[bwible]

Based on this equation I think my efficiency is in the 63% range. 1.030 gravity with 6.5gal in the boil pot. Was aiming for 1.056.

Its all gravity points. 6.5 gal at 1.030 pre-boil = 6.5 x 30 = 195 total gravity points in the brew. 195 / 5 gallons suggests this would be 1.039 when boiled down to 5 gallons.

I experienced low gravity a few times when I used old grain that had been sitting for awhile, out of a 55lb sack. I hadn’t been brewing for awhile and it sat for maybe a year. Freshness of grain, others said grain crush? Another major cause of missed gravity is dough-balls or pockets of dry grain within the mash bed. Stir, stir, stir when mashing in. Grain that doesn’t get wet and thoroughly mixed in will not give up its sugar. I poo-pooed this idea too, until I found I was actually doing it.

Far as batch sparging, I’ve been doing that for ages and that by itself doesn’t cause a major loss of gravity points. Just do a slow runoff as others mentioned. Do you recirculate at least some of the wort back through the grain bed? That makes a difference. I used to do it manually using pitchers until I got an Anvil pump. Now I use the pump to recirculate, drain when it runs clear then add all my sparge water at once, let sit for a few min then drain slowly again.

 

[bracconiere]

Its all gravity points. 6.5 gal at 1.030 pre-boil = 6.5 x 30 = 195 total gravity points in the brew. 195 / 5 gallons suggests this would be 1.039 when boiled down to 5 gallons.

thanks for the quick math....

edit: it's weird, it even works when done in liters.....

 

[Gnomebrewer]

Based on this equation I think my efficiency is in the 63% range. 1.030 gravity with 6.5gal in the boil pot. Was aiming for 1.056.

Efficiency is the percentage you got out of a theoretical maximum, not a percentage of your target. You had 13lbs of grain. Potential gravity (ppg, or points per pound per gallon) varies for different grains; I'll use 1.036 (36 points) as an average estimate. 13lbs x 36ppg = 468 gravity points. You had 6.5 gal at 1.030, so had 195 points in the boil kettle. 195/468 = 42%. So your mash-lauter efficiency was around 42% using a crude estimate for grain potential. 6.5 gallons at 1.056 would have been 364 points, which is 78% efficiency - a reasonable target for single batch sparge system.

It's apparent from this that your issue is either conversion efficiency (eg. crush) or lauter efficiency (sparge) or a combination. There's nothing you've mentioned about your process that is fundamentally wrong. Your efficiency should be better. Take measurements throughout the brewing process on your next brew to find out where the issue is.

 

[RM-MN]

6lbs of wheat malt

Wheat is smaller and harder than barley so it often does not get crushed well if at all. Without crushing you get very little conversion so you efficiency takes a big hit. If your supplier mixed the grains before crushing they had the mill set too wide to crush wheat malt.

Now that you have had problems with efficiency for more than one batch it is time to get your own mill and get away from the problems of too coarse of a crush. Until you do you are at the mercy of whomever you buy grain from.