Spike Brewing 12.5 Conical Fermenter Giveaway!

Home Brew Forums > Home Brewing Beer > All Grain & Partial Mash Brewing > Partial Mash Question - mash temperature too high, low O.G.?

Reply
 
LinkBack Thread Tools
Old 08-16-2010, 01:46 PM   #1
KSR
Feedback Score: 0 reviews
Recipes 
 
Join Date: Aug 2010
Location: Richmond, VA
Posts: 9
Default Partial Mash Question - mash temperature too high, low O.G.?

Long-time lurker, first-time poster here.

I started brewing PM batches a few months back after brewing extract for over a year, the first two batches were kits from AHS and they came out great. Once I felt that I had the technique pretty much down I started playing around with formulating my own recipes and riffing on others using BeerSmith. All of those came out right on target as well. However, I picked up two more AHS kits for my most recent brews and I've run into issues with the O.G. coming in around .008-.010 lower than expected in both batches.

While mulling it over in the shower this morning, I realized that I'd followed AHS's instructions to the letter in both of those batches EXCEPT for the mash temperature: I'd gotten used to heating X qts. of water to 168 as per BeerSmith's mash calculations for my custom recipes. AHS's PM recipes call for heating 2.5 gal. to 160F and holding the mash at 155. So what did I do? I heated 2.5 gallons to 168 out of habit and mashed 3lb. 2 oz. of grain in it for 60 minutes. Because I'd gotten overconfident I neglected to take a mash temperature reading, but I ran the numbers through BeerSmith and according to it, that resulted in a mash temp of 161. I did do a starch conversion test with both batches and the results told me that everything had converted, i.e. the iodine didn't turn purple or black.

I didn't worry about any of this with the first batch batch that was off, but now it looks like something's up.

I'm certain that this isn't just an issue of the extract not mixing with the top-off water. I'm a big guy and have no problems thoroughly shaking the fermenter for 5+ minutes, and I've never had any problems with mixing in my previous 30-some batches.

The expected O.G. for the last batch was 1.052, reading came in at 1.044. The grain bill is 10oz. c-20l, 2lb 2-row pale malt, and 5lb extra pale liquid extract.

Sorry about the long exposition, my question is this: could mashing at a higher temperature account for a nearly .010 difference in my O.G. even though the iodine test told me that conversion was complete? At this point I feel like it's either that or my hydrometer is wrong. Thanks.

__________________

Last edited by KSR; 08-16-2010 at 03:03 PM.
KSR is offline
 
Reply With Quote Quick reply to this message
Old 08-16-2010, 04:34 PM   #2
artongue
Feedback Score: 0 reviews
Recipes 
 
Join Date: Dec 2009
Location: Austin
Posts: 11
Default

What temperature was your wort when you took the hydrometer reading? Have you tested it in plain water?

You could try lowering your mash water volume a little bit and performing a mini sparge. That will help you get those ever so important sugars left behind in the grain.

The high mash temp can be the culprit for low extraction, but it doesnt sound like it in your case since you did the conversion test.

__________________

Last edited by artongue; 08-16-2010 at 04:58 PM.
artongue is offline
 
Reply With Quote Quick reply to this message
Old 08-16-2010, 06:04 PM   #3
KSR
Feedback Score: 0 reviews
Recipes 
 
Join Date: Aug 2010
Location: Richmond, VA
Posts: 9
Default

It was at 68 when I took the reading, so even after correcting for temperature it was pretty far off. I tested the hydrometer in 70 tap water today and it read 1.002 (uncorrected), which struck me as odd but I know that it's supposed to be tested in distilled water so I'll need to try that too.

Could you explain what you mean by mini sparge? I always put the grain bag into a colander over the pot and pour 170F water over the grain after the mash is finished. Is that the same thing?

I guess the thing to do is to go buy a different hydrometer and compare readings from the two to determine if that's the culprit.

__________________
KSR is offline
 
Reply With Quote Quick reply to this message
Old 08-16-2010, 07:07 PM   #4
Pivovar_Koucky
Feedback Score: 0 reviews
Recipes 
 
Join Date: Feb 2010
Location: Cincinnati, Ohio
Posts: 399
Liked 8 Times on 8 Posts
Likes Given: 8

Default

Quote:
...and mashed 3lb. 2 oz. of grain in it for 60 minutes
Quote:
The grain bill is 10oz. c-20l, 2lb 2-row pale malt, and 5lb extra pale liquid extract
It looks to me like you mashed 2 lb. 10 oz. into 168 F. water, unless I missed something. Was there another grain? Because I think that 1.052 is optimistic with that grain bill. You'd have to top 90% efficiency which is unlikely in the best of circumstances.

Also, a higher temperature can mess with your efficiency. But it looks like you are getting ~50% efficiency from your PM, which isn't great, but considering you don't really sparge it's not awful.

If you want to bump your efficiency you could heat up a second pot of water to 170 F and transfer your grain bag to that for 5-10 min to extract more of the sugars. Just pouring hot water through the grains won't extract very much sugar.

They main thing to worry about with a high mash temperature is getting a lot of unfermentable sugars and bad attenuation as a result.
__________________
Pivovar_Koucky is offline
 
Reply With Quote Quick reply to this message
Old 08-16-2010, 07:25 PM   #5
KSR
Feedback Score: 0 reviews
Recipes 
 
Join Date: Aug 2010
Location: Richmond, VA
Posts: 9
Default

Oops, sorry. That should have read 2.5 lb. 2-row pale malt.

I'll try the heating up a pot next time around and see how it goes.

__________________
KSR is offline
 
Reply With Quote Quick reply to this message
Old 03-15-2011, 04:54 PM   #6
bmantzey
Feedback Score: 0 reviews
Recipes 
 
Join Date: Jun 2010
Location: Rome, NY
Posts: 153
Likes Given: 3

Default

I read somewhere that if you mash at a higher temperature, you get sweeter, less fermentable wort and if you mash at a lower temperature, you get a dryer, thinner bodied beer. The higher temp was said to be 158° or higher and the lower temp was said to be at or below 150°.

__________________
bmantzey is offline
 
Reply With Quote Quick reply to this message
Old 03-15-2011, 05:18 PM   #7
Pivovar_Koucky
Feedback Score: 0 reviews
Recipes 
 
Join Date: Feb 2010
Location: Cincinnati, Ohio
Posts: 399
Liked 8 Times on 8 Posts
Likes Given: 8

Default

Quote:
Originally Posted by bmantzey View Post
I read somewhere that if you mash at a higher temperature, you get sweeter, less fermentable wort and if you mash at a lower temperature, you get a dryer, thinner bodied beer. The higher temp was said to be 158° or higher and the lower temp was said to be at or below 150°.
Yes, that is accurate in general; however, there are other factors which can also have an effect. If you are partial mashing, the fermentability of your extract will play an enourmous role in the final gravity/body of your beer.
__________________
Pivovar_Koucky is offline
 
Reply With Quote Quick reply to this message
Old 03-15-2011, 08:12 PM   #8
KSR
Feedback Score: 0 reviews
Recipes 
 
Join Date: Aug 2010
Location: Richmond, VA
Posts: 9
Default

Just to follow up, I ended up buying a 5 gal cooler with a false bottom and have been using that to make "big" partial mashes (20 - 30% of the fermentables are coming from extract, the rest from grain), and have been consistently getting 75 - 78% efficiencies while doing batch sparges with that setup. So, I think the problem definitely came down to poor mash temp control on my part and insufficient sparging when using the brew in a bag method.

__________________
KSR is offline
 
Reply With Quote Quick reply to this message
Old 03-15-2011, 08:18 PM   #9
Walker
I use secondaries. :p
HBT_LIFETIMESUPPORTER.png
Feedback Score: 0 reviews
 
Walker's Avatar
Recipes 
 
Join Date: Sep 2005
Location: Cary, NC
Posts: 11,235
Liked 72 Times on 64 Posts
Likes Given: 11

Default

A higher mash temp won't affect OG as long as you are waiting for starch->sugar conversion to happen.

You can get a higher or lower final gravity depending on the mash temp because you have different sugars produced in the tun, but a fully converted mash at 148 and a fully converted mash at 158 should have the same OG.

__________________
Ground Fault Brewing Co.
Walker is offline
 
Reply With Quote Quick reply to this message
Reply


Quick Reply
Message:
Options
Thread Tools


Similar Threads
Thread Thread Starter Forum Replies Last Post
High Mash Temperature tbone All Grain & Partial Mash Brewing 6 10-03-2011 04:53 AM
Partial Mash (Mini Mash Tun) Question hbhudy All Grain & Partial Mash Brewing 11 10-13-2010 12:39 PM
First Partial Mash. REALLY high OG. SeldomSeen All Grain & Partial Mash Brewing 16 02-20-2010 02:09 AM
Maibock mash temp question (Partial mash) motobrewer All Grain & Partial Mash Brewing 5 12-30-2009 05:13 PM
Partial Mash Temperature Reading dipflop All Grain & Partial Mash Brewing 3 07-17-2008 05:12 PM