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-   -   Extra 15 minutes of mash? (http://www.homebrewtalk.com/f36/extra-15-minutes-mash-74160/)

jpsloan 07-28-2008 11:27 PM

Extra 15 minutes of mash?
Ok, so. I've done three AG brews so far. The first and third were Biermuncher's Centennial Blonde ale. Both times, I ended up with a final gravity of 1.032, which is about 16 points less than what Brewsmith says it ought to be (1.048). The recipe is 8-3/4lbs of grain, with a 11 qt mash at 150degrees, and a 4.5 gallon sparge @ 180degrees, split in half.

Forgiving the crush that I get from AHS, I pretty much follow the double batch sparge method with no mash out. I went through my settings in Brewsmith, and I found one key, salient point that I had missed both times.

The program asks for a 75 minute mash. I've only been giving it a solid hour before vorlauf.

So, here's my question: is that last 15 minutes of mash enough to make up for at least most of my final gravity sucktitude? Or is it only a minor thing, and I really need to contend with the crush (somehow), or adjust the sparge?

Beerrific 07-28-2008 11:30 PM

Are you talking about final gravities after fermentation, or original gravity before fermentation?

I am thinking it is OG. So essentially you are not reaching the same efficiency that BM has his recipes set to. I can get 70% eff. with the crush from AHS. How are sure of your thermometer calibration?

avidhomebrewer 07-28-2008 11:50 PM

Do a starch test. Take some of the wort and add some iodine to it, in a separate container. If it turns black, let it go for another 10 minutes and repeat. I do a 90 minute mash with all my batches and my gravity is close (a couple points either way) to what is called for. How confident are you in the hydrometer reading? Are you correcting for temperature when you calculate the hydrometer reading?

wurt 07-29-2008 12:21 AM

It is really difficult to know what the problem is without seeing your method.
Generally, 15 extra minutes of mashing won't increase your efficiency. Actually, there is some debate as to whether a 60 minute mash is even required. I've had success with mashes shorter than 40min.

Here is a few factors that might be affecting you:
1. The recipe seems to assumes ~70% efficiency, which is pretty good, and only really achievable if you are continuously sparging. I personally prefer batch sparging, but have never gotten above 65% efficiency from a batch sparge.
But your efficiency seems to be more like 50%.
2. Maybe your crush isn't very good
3. Do you mix your mash well to assure that you have no dry pockets
4. Hydrometer readings could also be a bit off.
5. Does your final volume match what the program gives you?

It is still really surprising that you would be low by 16 gravity points, but maybe the combination of a few of these factors is getting you there.

Also, why are you using 180degree sparge water. With batch sparging you don't worry about extracting tannins, as much as in continuous sparging but at 180degrees you might actually extract some. Plus if you are not mashing out you aren't really denaturing that enzymes anyway, so why risk adding 180degree water to your grainbed.

jpsloan 07-29-2008 12:49 AM

Ack... yes. I mean Original Gravity after boil. I'm a dink.

I have never calibrated my thermometer, and I think that would be worthwhile. I appear to be achieving my temperatures as predicted by Brewsmith, so I haven't had any red flags that indicated I was missing them, but I will look into that.

I will also do a check on my hydrometer... I have an extra (came with the wine kit), which makes this easy.

I don't have any real control over crush. I haven't seen several thread screaming at Forrest to improve on his mill, so I figure others have done well with it so far. I do give the grist a thorough stirring at dough-in, and then again prior to the first vorlauf... and each time I add the sparge water. However, there is a possibility that I'm shying off the bottom of the MLT for fear of knocking loose my braid (it's just kind of sleeved onto the vinyl tube since I'm a dink, and can't figure a decent way to attach it to the barb with hose clamps). So, it's a possibility that there's sugars down there at the very bottom that could be stirred into suspension better.

So, the extra fifteen minutes might not be a significant factor? I did a Witbier for my second batch, but I was in a little stormcloud of chaos and managed to not check the gravity on that one.

wurt 07-29-2008 01:07 AM

What temperature are you taking your hydrometer reading at? And what is you hydrometer calibrated to 60degrees or perhaps 68? You can use a site like this:
to correct it.
A scratch test may be useful. After three all grain batches the best approach is to try again. It can take a while to learn your system.

TexLaw 07-29-2008 02:52 AM

Unless you are working with poor mashing conditions, you should not need a 75 minute mash to reach your OG. The only difference you should see between a 65 and 70 minute mash there should be for fermentability.

That said, if you are working with poor mashing conditions, then you might need that other 15 minutes. The recipe probably says to go 75 minutes "just to be sure." Like avid said, the only way you know what is in your mash tun is to do an iodine test (you can use iodophor).


jpsloan 07-29-2008 01:42 PM

Alrighty. Thanks for the replies, guys. I have some equipment calibration checking to do. And Sunday, I'll be doing another batch, and I'll do an iodine test to see if I'm converting. I'll also work towards measuring volumes and gravities as I go this time, in an effort to quantify what's happening more precisely.

Choguy03 07-29-2008 02:54 PM


1. The recipe seems to assumes ~70% efficiency, which is pretty good, and only really achievable if you are continuously sparging. I personally prefer batch sparging, but have never gotten above 65% efficiency from a batch sparge.
But your efficiency seems to be more like 50%.
I disagree with that. I have done two AG's and have gotten 82% and 78% while batch sparging. I would say that more sparge water, better mixing. Hitting strike and mash temps are all more important to look at. Your water-grain ratio looks to be ok, but I always shoot for ~ 1.5 quarts/lb of grain. But I don't know how much that would change your efficiency.

TheH2 07-29-2008 03:26 PM

I would recommend checking for starch conversion. It is very easy to do and will prevent you from draining the mash before it is ready, which I would assume will increase efficiency.
Last time I mashed it took 75 minutes at 152 degrees for conversion (my spoon wasn't big enough to get a very good stir). If you don't have iodine (easy to find at drugstore/grocery store) make sure the wort has an iridium shine to it before draining.

My efficiency was 77% and I batch sparge in a 48 quart cooler with a double sparge.

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