Partial Mash Mystery

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catalyst156

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I put together a partial mash recipe based on Jamil's Lagunitas IPA clone (AG) found here: http://beerdujour.com/Recipes/Jamil/JamilsLagunitasIPA.htm

After mashing the grains and topping off the kettle, I stirred the wort to get a good distribution and took a sample for a gravity reading. Pre-Boil Gravity: 1.025 from a volume of approximately 3 gal. The rest of the fermentable sugar came from 6 lbs LME to reach an estimated OG of 1.061 I finished the brew and before pitching the yeast (again, lots of shaking to aerate and homogenize the wort) I took another sample. This time it read 1.051 which is 0.010 lower than expected. Now, I have three questions.

1) Based on the information I can find, it looks like you should expect approximately 37 points ppg from 1 lb of LME (I know it will vary, but that's a good rough estimate). Therefore, I'm estimating that I should have got a reading of 1.060. (Pre-Boil OG * partial boil gravity/batch size + LME addition == 1.025 * 0.6 + 45 == 1.060). Either I mismeasured the top-off water (which I know I did not because my carboy is marked at the 5 gal mark) or the LME was really weak (~30 ppg). Is that suspect?

2) It's only been in the fermenter for a few hours, would a DME addition hurt anything at this point?

3) I was planning on dry-hopping with another 4 oz of Willamette (4.7% AA), but if it's going to be weaker than expected (more of a session IPA I guess), should I forgo the dry-hop? I don't want a 2xIPA. I guess the logical thing to do would be to taste it at the 2 wk mark and see how much of the hop aroma has been retained and make a decision at that point. Yes?

Thanks for the help!
 
I had really low gravity readings on a couple of partial mashes & posted about it on here. the conclusion i drew, with some helpful input from board members, was that i was not mixing the top off water well enough with the wort.

are you just shaking your fermentor or mixing with a paddle? I wouldnt think that you could physically shake up 5 gallons of liquid adequately enough to get the thick wort from the bottom to fully mix with the top off water. I have no evidence to back this up it just seem like a stretch to me. Id suggest making this same beer again & try getting a paddle, or some other device that you can trust to not be infected with all sorts of junk, and mix your next batch up thoroughly and see if there is a difference.

i would doubt that it is due to inferior quality lme.

edit: you certainly could add dme at this point, i would boil it in some water for 15-20 min first and pour it in slowly trying not to splash at all. i did this on the first of those two beers i made with a low gravity readings... ended up with a beer that was quite a bit higher in alcohol, because as previously mentioned all the fermentables were in the wort after brewing, it just wasnt mixed well.
 
@ Xeno:

Thanks for the responses. The fermenter was shaken, not stirred. In all honesty, I'm not sure how you'd get a stirring device down into a carboy, but I'll leave that for another day. I thought I was shaking it rather efficiently, but I took another look at it just now and it seems as though there might be a thinner/more watery layering towards the top. This is the first batch I haven't picked up and shaken manually. I stopped doing that because I was afraid of losing my grip on sending several hours of work flying across the room in a messy and dangerous disaster.

I guess I'll assume it's all there (just not well mixed), and move forward to see what happens.
 
I did my first partial mash yesterday and ended up at 1050 when the recipes OG was 1060. I didn't mix the wort well after topping off with water in the primary. I only shook the bucket with the lid on.

My digital thermometer went haywire during the mash in the oven. 30mins in, it shot up to 190 from 152 (oven temp 170). I turned off the oven and opened the door. After 10 mins the temp didn't drop on the digital thermometer so I took a reading with my dial thermometer and it was 140. For the remaining 15 mins I left the oven on 170. Not sure how efficient my mash was since I have no clue at what temp I mashed at. I was thinking this may be why I had a lower OG reading.
 
@ Xeno:

Thanks for the responses. The fermenter was shaken, not stirred. In all honesty, I'm not sure how you'd get a stirring device down into a carboy, but I'll leave that for another day. I thought I was shaking it rather efficiently, but I took another look at it just now and it seems as though there might be a thinner/more watery layering towards the top. This is the first batch I haven't picked up and shaken manually. I stopped doing that because I was afraid of losing my grip on sending several hours of work flying across the room in a messy and dangerous disaster.

I guess I'll assume it's all there (just not well mixed), and move forward to see what happens.

ha, good point on stirring in the carboy, i guess i forget that im probably in the minority using a plastic bucket for fermentation....

Until you get to the point where you're doing full boils your best bet for determining OG might be to take a sample of your mini mash. Get a gravity reading on that, making sure to take note of your total volume of wort. From that you can determine your total gravity points from your mash; if you have 2 gallons @ 1.060 that is 120 total gravity points (you should be doing this anyways just to see how efficiently you are mashing/sparging). Next add your gravity points from your extract, use the whatever the typical values are, i forget them but i think dme is something like 40 gravity points per gallon. So if you add 4 pounds of dme thats another 160 points for a total of 280, divide by your batch size(probably 5 gallons) & you get 1.056 OG. This obviously doesnt account for minor loses along the way like your hops soaking some wort up, etc., but gives you a decent ballpark.

The other option would be to just go get a plastic fermentor for the purposes of adding topoff water & aerating, then transfer to your carboy. This adds a step & more potential for infection, but if accurate OG readings are really important to you it might be worth it.

There must be other people on here brewing the same way as you; partial mash, adding topoff water in a carboy, anybody else have any good methods for him to ensure a good mix of water & wort?.....
 

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