Original gravity

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Original gravity

Postby mikec51 » Tue Dec 01, 2009 4:05 pm

HI, I keep missing my original gravity on most of the beers I have been brewing since I went to all grain. Last was a red ale with a calculated OG of 1.059 and it came in at 1.048. Similar results on previous brews. Beers that were supposed to be 5.5% ABV are 4.7% - 4.8%. I'm using a 7 gallon cooler with a false bottom from Midwest Supplies for mashing at a pretty consistent 155 degrees. I'm using a HLT with a sparge arm and it's taking around 45 - 60 minutes to sparge completely. I'm using iodine to test for conversion which has been taking 60 - 90 minutes. Any suggestions on getting the OG where it's supposed to be?

Thanks,

Mike
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Efficiency

Postby slothrob » Tue Dec 01, 2009 10:56 pm

It seems that your efficiency is a bit low.
The two places where you can take a hit on your efficiency are Conversion and Lautering. If you record the gravity of your first and second runnings and the volumes you add, you can calculate the Conversion Efficiency and Lauter Efficiency. Once you locate where you are losing efficiecy, it's easier to narrow down good approaches to solve the problem.

Kai Troester runs this great site for learning about troubleshooting efficiency and has the resources you need to determine your Conversion and Lauter Efficiencies.
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Efficiency

Postby mikec51 » Wed Dec 02, 2009 2:01 pm

OK, I'm brewing Saturday so I'll check it and get back to you. Thanks
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Efficiency

Postby slothrob » Wed Dec 02, 2009 5:20 pm

Kai supplies this spreadsheet for doing all the calculations, but you can get a pretty accurate idea from this table:
Image
Measure the gravity of your mash liquid and compare that to the value the table says it should be for your mash thickness. When the mash is complete, you should be approaching 100% conversion (at least well into the 90s.) If not, the mash needs to run longer and might benefit from a step up to 155-162F to force conversion to finish. Conversion efficiency is heavily influenced by how well the grain is crushed, so if this area is a problem, you may want to look into making the mill gap tighter or double crushing.

The difference between the total sugar in your mash, and the amount you get out will tell you your lauter efficiency. The calculation gets a little screwy without the spreadsheet, because of the water absorbed by the grain and the volume increase from dissolved sugars, but essentially the difference between your Conversion Efficiency and your Mash Efficiency is your Lauter Efficiency. Lauter Efficiency is influenced heavily by the size of the grain bill and how much water you sparge it with, but also the amount of dead space in your tun and channeling of the flow through the grain bed (if fly sparging). That last factor can be removed as a variable and analyzed by trying a batch sparge and comparing it's efficiency to a similar gravity beer that was fly sparged.
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Efficiency

Postby mikec51 » Sun Dec 06, 2009 11:54 pm

Well, this amateur needs some direction. I brewed a brown ale with the following grain bill: 8.5# Maris Otter, 1# Caramel 80L, .75 # Belgium Aromatic, >75 # Belgian bisciut, .25# chocolate. I mashed at a ratio of 1.5/1. Collected 6.5 gallons into brewpot. OG prior to boil 1.030, considerably low! Mash pH = 5.2. If my math is correct extraction = 17.3, mach effriciency 47%. OG in fermenter = 1.045, predicted 1.057. Starch test was perfect. I used a single infusion mash at 155 degrees F. Recirculated and lautered right at 45 mins. I have been getting my grains pre-crushed from Midwest Supplies. I have only done a few all grain recipes and these results are pretty typical. Most of the beers have tasted pretty good, just missing the mark on gravity. I brewed this same recipe a few months ago with similar results, but comments were the beer was as good as any premium you could buy! That's great to hear but I'm obviously falling short somewhere. I'm guessing the low extraction is the problem. How do I get it up to the 27 - 30 range? Will that in turn improve efficiency? Another question I have is what is optimum time to bring the wort to a boil, and what would the absolute maximum be? If it takes too long what are the effects on the beer? Thanks.

[img][/img]
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Re: Efficiency

Postby slothrob » Mon Dec 07, 2009 7:53 am

Did you get the gravity of your first runnings? Meaning the gravity of the wort in your tun at the end of the mash, after recirculating, but before you add sparge water.

That will give you your conversion efficiency. Gravity is much more informative than the starch test for determining problems with conversion.

For your efficiency to be that low, you're almost guaranteed to be getting incomplete conversion as well as some lautering problems. What is your manifold design? What is your dead volume?

You're pushing the mash time for someone getting low efficiency. I think you might want to take a gravity reading at 1 hour, then if you don't have close to 100% conversion, then mash for 90 minutes.

Also, I'd recommend doing an experimental batch sparge. Batch sparging will eliminate the variable of channeling, which will help diagnose the problem.
mikec51 wrote:Another question I have is what is optimum time to bring the wort to a boil, and what would the absolute maximum be? If it takes too long what are the effects on the beer? Thanks.

I'm not sure what you mean by "time to bring to a boil."
Are you wondering if it's taking too long to bring your runoff to a boil?
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Postby mikec51 » Mon Dec 07, 2009 12:28 pm

Yes, it may be taking too long to come to a boil. The gravity of the first runnings was 1.065. My mash/lauter tun is a round 7 gallon cooler with a false bottom. I'm also using a sparge arm. So I used the wrong gravity figure to calculate conversion efficiency? My dead volume is 68 oz.
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Efficiency

Postby slothrob » Mon Dec 07, 2009 4:17 pm

mikec51 wrote:Yes, it may be taking too long to come to a boil. The gravity of the first runnings was 1.065. My mash/lauter tun is a round 7 gallon cooler with a false bottom. I'm also using a sparge arm. So I used the wrong gravity figure to calculate conversion efficiency? My dead volume is 68 oz.

I like those 7 gallon coolers, they're a great size for 5 gallon batches.

For Conversion Efficiency, you need that gravity of the First Runnings, because you want to compare the gravity of the mash liquor, independent of any losses due to Lautering efficiency, to ensure that your mash is running to completion. For reference, you should see conversion rates of approaching 100%.

With the numbers we have now, we can learn a lot of interesting things.

If you take your mash ratio of 1.5 qt/#, you can refer to the table I posted above and see that your First Running's gravity would be expected to be 1.082. The 1.065 that you actually measured indicates that you had a Conversion Efficiency of 65/82 x 100 = 79%. Your conversion didn't approach completion during your mash.

Factors you can change to achieve completion are:
-crush finer
-mash longer
-step your mash to a warmer rest to improve starch gelatinization and push enzyme activity to complete conversion.

What I would recommend, if you have no control over your crush (though you could request a double-crush, and they might do that for you) is to use that table and refer to it when you reach the end of your mash. If you are not well into the 90's on percent conversion, then you should let the mash run longer; 90' or more if you need to. Recirculation may help this progress.

If you don't see the gravity increasing significantly enough or if it is slow, then you can increase the temperature of the mash, after the first rest, with a hot water infusion. Pushing the mash into the 155-162F range can accelerate conversion. I will often use 158F, just because it's toward the middle of that range.

We also now know that, given a Conversion Efficiency of 79% and your calculated Mash Efficiency of 47%, that your system has a Lauter Efficiency of 47/79 x 100 = 59.5%.

This means that, had you had complete conversion you would have pushed your Mash Efficiency to nearly 60%.

I still think that your Lauter Efficiency is also low. I would expect it to be 70%-85%. This indicates that there is a significant inefficiency in draining your tun or rinsing the grain. I again would recommend a trial Batch Sparge to remove the possibility of channeling during your sparge, but a false bottom should preclude this possibility and the large Dead Volume is concerning.

People can sometimes refer to 2 different things as Dead Volume. Brewers who use false bottoms will sometimes call the volume below the false bottom the Dead Space, but for the purposes of improving Lauter Efficiency, I'm talking about the amount of liquid that would remain in your tun if you filled it with water, opened the valve and drained it until the water stopped flowing out on it's own.

If you really leave 68 oz in your tun after a complete drain, then this is probably the cause of your low Lauter Efficiency (for reference, the dead volume in my tun is a little over a cup and you should be able to reduce yours to closer to a pint.) The solution to this is to build a dip tube that goes from your false bottom to the actual bottom of the tun. This will allow the liquid to drain completely and prevent leaving a lot of high gravity wort under the false bottom that needs to try and mix with the sparge water during the sparge.
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Postby mikec51 » Mon Dec 07, 2009 7:20 pm

slothrob,

Thanks for all the info. I'll check my mash tun and see what I can do to lower the dead volume. I filled it above the false bottom this morning and let it drain, then measured the volume left and it was definitely 68 oz.

So the other question re. the time it takes to reach a full boil? I think I'm taking too long trying to do the whole 6.5 gallons on the stove. I don't have a large burner yet. I read you can split the wort and boil in 2 pots, just be sure the hops are divided in the same ratio. Any thoughts on this?

Thanks
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2 pot boil

Postby slothrob » Mon Dec 07, 2009 7:50 pm

You can boil in 2 pots, and I've done it. It's a decent stop-gap move, but it will probably increase your boil-off and kettle caramelization. I'm actually surprised you can bring 6.5 gallons to a boil on a stove.

How long is it taking to get to a boil? I think that it isn't really important how long it takes, unless you are spending a long time below 170°F and find that you're beers are finishing too dry and you can't correct for that by raising your mash temperature.

Another option is to collect about half your volume and start that on the stove, then collect the rest of your runnings, which should be warmer, in another container and add that to the hot wort on the stove. If you mash out, and sparge the grain bed at 170°F, it shouldn't make much difference if it takes a little time to get to boil, though. If the wort is sitting around at less than 158°F for a long time, you might get a drier beer.
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Postby mikec51 » Tue Dec 08, 2009 1:53 pm

It takes about 45 min. to get to a boil. I've been thinking about the dead volume. The false bottom is dome shaped and is about 7/8" high in the center. I came up with the 68 oz. by filling the tun above the false bottom and then draining it. I don't think this is an accurate # as the grain is pretty much on the bottom all around the edge and displaces some of that water. I'll have to completely drain it with my next batch to get a closer number. I put a short nipple on the drain tube inlet and got 64 oz. Not sure why it's different from my first #. I think the nipple will allow me to draw wort closer to the bottom, but will not decrease the dead volume as I haven't changed the height of the drain.
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dead volume

Postby slothrob » Tue Dec 08, 2009 4:06 pm

I started with around a couple quarts of dead volume and 50% efficiency.

What I did to solve the dead volume problem was to run a dip tube to the bottom of the tun from the outlet valve (and tubing from the valve to the kettle to maintain a siphon, since I Batch Sparge.)

What a lot of brewers with false bottoms do is to run a tube from the center of their false bottom to the bottom of the tun. While you are Fly Sparging, it shouldn't matter that the valve is above that tube's inlet, it will still continue to draw from the bottom of the tun.

I think that connecting tubing to your outlet valve would be unnecessary on brew day, if you don't want to, but you would need to temporarily connect tubing to get an accurate measure of the dead volume by allowing a siphon to draw the liquid down to the collection point of the dip tube below the outlet.

It's true that grain will take up some of that space, but the smaller the better (within reason). My dead space is a little over a cup without grain.
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