Added a gallon starter b4 taking OG. What was my real OG?

[gigapunk]

I made a 4.5 gallon partial-mash batch of bohemian pilsner today. BeerSmith said it should have had an estimated OG of 1.044

Three days ago I made a gallon starter of wyeast bohemian pilsner yeast.

My original wort (including sparge) was about 3 gallons. I then added the gallon starter, and then topped off the last 0.5 gallons with filtered water to the fermenter.

I forgot to take an OG before adding the starter and topping off. I just took. a specific gravity reading and I'm at 1.024 not the predicted 1.044.

This is already not a very strong recipe, with a predicted ABV of 4.3. I'm worried that I had very poor conversion, and am considering boiling a concentrated bit of DME to add to the wort. For my mash I just held the grains at about 156 for 30 minutes in 2 gallons, and then sparged at 170 for 40 min in 1 gallon, and then combined the two pots, brought to a boil and added the LME then hops.

Or maybe I'm just over reacting? And a gallon starter is likely to have lowered my (perfectly converted) wort from the 1.044 it really was (and would have been had I measured at the correct time) to the now just fine 1.024?

Help?!

 

[a10t2]

You'd need to know the gravity of the starter to get a precise answer; however, assuming it was 1.010:

(x*3 + 1.010*1 + 1*0.5)/4.5 = 1.024, solving for x gives about 1.033.

 

[weirdboy]

Assuming you mixed everything well before taking the sample, your OG is the one you took.

I mean, that's the gravity of what's in there and fermenting...

Anything else isn't really your OG.

 

[gigapunk]

Everything I've read says that you have to take the OG before adding the yeast. Is that not correct?

 

[weirdboy]

The idea behind taking the reading before adding the yeast is because the yeast is going to ferment the wort, thereby reducing the gravity. But if you are measuring the gravity right after pitching, it's the same. Don't pitch, and then check gravity hours or days later, because that number is not going to be correct.

 

[gigapunk]

Thank for all the help guys! It's a good thing I havn't tried All-Grain yet...

I added about 2.5 lbs of light DME in less than a gallon. New OG is 1.054.

 

[dcp27]

You'd need to know the gravity of the starter to get a precise answer; however, assuming it was 1.010:

(x*3 + 1.010*1 + 1*0.5)/4.5 = 1.024, solving for x gives about 1.033.

You'd need to know the OG of the starter not the FG as whatever alcohol has already been formed is added as well, not just the remaining sugar. Add however much extract was used for the starter to your recipe. However, considering the 3.3lbs of LME alone in 4.5gallons is 1.026, clearly some fermentation has already taken place and its not possible to figure out your true OG at this point. Just remember to take it prior to pitching next time.

 

[gigapunk]

I keep screwing up, and I keep getting beer anyway...

This is a great hobby.

 

[a10t2]

You'd need to know the OG of the starter not the FG as whatever alcohol has already been formed is added as well, not just the remaining sugar. Add however much extract was used for the starter to your recipe. However, considering the 3.3lbs of LME alone in 4.5gallons is 1.026, clearly some fermentation has already taken place and its not possible to figure out your true OG at this point. Just remember to take it prior to pitching next time.

I'm sorry, but that's not correct. The FG of the starter is affected by the presence of alcohol, but that doesn't change its value. Fluids of different specific gravities, when mixed, sum proportionately. Adding a gallon of 1.010 liquid that's 4% ethanol and a gallon of 1.010 liquid that's only water and sugar will change the resulting solution's SG by exactly the same amount.

For that matter, you *can* determine the effective OG of the full 4.5 gallons. You just need to know both the OG and FG of the starter. FWIW, assuming the starter fermented from 1.040 to 1.010, the OG for the 4.5 gal would be 1.031.

edit: But based on the most recent reading of 1.054, it sounds like the wort wasn't well-mixed before taking the 1.024 reading. The OG was almost certainly between 1.060 and 1.070, but at this point you'll probably never know exactly what it would have been.

 

[dcp27]

I'm sorry, but that's not correct. The FG of the starter is affected by the presence of alcohol, but that doesn't change its value. Fluids of different specific gravities, when mixed, sum proportionately. Adding a gallon of 1.010 liquid that's 4% ethanol and a gallon of 1.010 liquid that's only water and sugar will change the resulting solution's SG by exactly the same amount.

agreed 100%, but the way you originally stated it only accounted for the 1.01 liquid which is why he'd need to know the OG. Either way, the FG of the starter is irrelevant to the OG of the total 4.5gallons, as it would just be the sum of the OGs. (I think were essentially saying the same thing, but in different ways)

So now knowing the starter was 2.5#dme in 1g, the real OG would be (3x + 1.110)/4.5, which like a10t2 said, most likely puts you in the 1.060-1.070 range, as x would be from about 1.04 (0% eff) to 1.075 (100% eff)

 

[a10t2]

agreed 100%, but the way you originally stated it only accounted for the 1.01 liquid which is why he'd need to know the OG. Either way, the FG of the starter is irrelevant to the OG of the total 4.5gallons, as it would just be the sum of the OGs. (I think were essentially saying the same thing, but in different ways)

OK, I read the OP as wanting to know the OG of the original 3 gallons, to compare to the expected 1.044. So yeah, we're agreeing, just answering different questions. Sorry about that.

So now knowing the starter was 2.5#dme in 1g, the real OG would be (3x + 1.110)/4.5, which like a10t2 said, most likely puts you in the 1.060-1.070 range, as x would be from about 1.04 (0% eff) to 1.075 (100% eff)

I think he added an *additional* 2.5 lb DME and <1 gal water. So now it's (3.3*37 + 2.88*37*Eff + 0.9*43 + 2.5*43)/5.25, assuming the total volume is 5.25 gal and the OG of the starter was ~1.040. That ranges from 1.051 to 1.072, depending on the mash efficiency.

 

[gigapunk]

It's nice to know that I can back calculate proportionally. I thought that an OG in the 1.030s was too low. So I tried to bump it up with a late addition of the DME in ~1g. The 1.054 was after that was added to the original mess. And the 1.054 was taken from the total 5+ gallons after mixing in the extra DME solution.

I think that this keeps happening to me (low conversion) because I keep overshooting my mash temps. With my partial mashes I'm usually trying to mash 4-5 lbs of grain in about 2.5 gallons of water, in my 5 gallon Aluminum pot on the stove. I've started using two thermometers (one probe, one floating) and stirring more. But it seems like I'll move the thermometer and it will go from reading 148 to 170! Then I'll throw in some water and turn off the flame and stir like crazy... I'm trying to stir more and keep a closer eye, but this is getting silly.

Will 170 for a few minutes destroy the enzymes that are needed for the mash?

 

[dcp27]

Will 170 for a few minutes destroy the enzymes that are needed for the mash?

The enzymes aren't denatured immediately, but they won't last too long (10mins maybe if you're lucky). It sounds like you keep the flame on while you're mashing? While you can mash at around 2qt/lb like you are, you'll have better temperature control around the standard 1.25qt/lb and may not need to keep the heat on and cause such fluctuations.

 

[gigapunk]

Thanx for the suggestion on improving my efficiency. That's exactly the kind of info I needed!

 

[dcp27]

Have you read death brewers partial mash guide yet: https://www.homebrewtalk.com/f39/easy-partial-mash-brewing-pics-75231/ ?
It may have a few more tips littered throughout to help you out

 

[a10t2]

While you can mash at around 2qt/lb like you are, you'll have better temperature control around the standard 1.25qt/lb and may not need to keep the heat on and cause such fluctuations.

Shouldn't it be the other way around? The more water, the smaller the fluctuations. And the less heat lost overall. You might be able to go to 3 qt/lb and only lose a couple degrees over the full hour, assuming it'll fit in your pot.

Either way, I'd turn the flame off after doughing in, stir for a couple minutes, and only turn it back on if needed.

 

[gigapunk]

Have you read death brewers partial mash guide yet: https://www.homebrewtalk.com/f39/easy-partial-mash-brewing-pics-75231/ ?
It may have a few more tips littered throughout to help you out

It was actually his thread that got me started on the partial mash! I'm using his methods, with my slightly inferior pots. I read upto about page 40, it's at 96 pages right now!!! Maybe it's time to go back to reading.

I just got done with a crazy oatmeal/rye american amber partial mash and got 78-80% efficiency! I had to use the same amounts of water to grain approximately. Here's what I did this time. Comments and Suggestion appreciated:

I added the grain bag 4.16 lbs to ~2 gallons of room temp water, and brought the whole thing up to 154 together. I tried to keep the heat very low to off, and to stir as much as possible. The mash frequently would go down to 147, and I'd have to heat it back up. I had to add some water in the middle to maintain my level (I think the pound of oatmeal sucks up a lot of water) I kept at it for a whole hour starting the timer after I had reached 154.

My sparge was a little over a gallon of water in a second pot at 177 degrees. I put the bag in, stirred a bit, and just put the lid on and forgot about it for an hour.

Combined the two, stirred in the LME, brought to a boil and did the hops.

What do you guys think about bringing up the temp with the grains rather than adding them to the hot water? My grains were 68% unmalted this time and I thought going through the protein and glucanase rest temps couldn't hurt.

 

[gigapunk]

You'd need to know the gravity of the starter to get a precise answer; however, assuming it was 1.010:

(x*3 + 1.010*1 + 1*0.5)/4.5 = 1.024, solving for x gives about 1.033.

I thought I should mention. I did a little experiment with this new batch today. Before thining out the wort I took a small sample from the brew pot, cooled it and took an OG it was 1.086. After adding a 0.4 gallon starter and some water for top off the formula predicted 1.056. When all was said and done I had a measured OG of 1.054! Pretty damn close!

 

[dcp27]

Shouldn't it be the other way around? The more water, the smaller the fluctuations. And the less heat lost overall. You might be able to go to 3 qt/lb and only lose a couple degrees over the full hour, assuming it'll fit in your pot.

Thats entirely possible. I cant remember my thermodynamics, but my thought was a thicker mash has a lower heat capacity, so it would take less heat to maintain the same temperature, and being on the stovetop, it would have the hot grid to make that happen.

 

[gigapunk]

The scientific term is "specific heat value". Its the amount of energy it takes to change the temp of something. VERY few things have as hi a "specific heat" as pure water. Anything you add to pure water, will make it easier to change the solutions temp.