Testing gravity of runoff

[Sir Law]

I've read in other posts that taking gravity readings of the runoff is not a good way to tell if you're done or not. Can someone please enlighten me as to why this is? My first attempt at an ag came up short with the og at 1.030. I don't want that to happen again so I was planning on testing the og from the runoff to see if I'm ok, but I'm reading that it might not be a good idea. Thanks.

[markaberrant]

There is nothing wrong with taking a pre-boil gravity reading, just make sure to compensate for the temp increase, and then calculate what the post-boil gravity should be. This will tell you if you need to add more water or more malt. BeerSmith (and probably ProMash) will calculate this all for you.

[hooky]

I test mine preboil to see where I'm at. Not a problem in the slightest. You're going to toss it back into the kettle to boil it anyway.

[dparsons]

If you're talking about testing the runoff to see when you're done sparging, that will tell you when you're at the end of the sugar (gravity < 1.010). The reason being that you can start to extract tanins if you keep sparging after the sugars are gone. Elsewhere on the site at least one member has indicated that proper pH stops this. I haven't confirmend.

Another quicker way is to do the same stick your finger in the wort flowing out of the tube and see if it tastes sweet. Once the gravity is down to 1.010 you won't be able to taste the sweetness any more and you can stop.

Perhaps your 1.030 OG is from stopping to soon? I haven't had a single batch where I stopped sparging before I collected my full pre-boil volume of wort.

[barleyburps]

I haven't had a single batch where I stopped sparging before I collected my full pre-boil volume of wort.

I concur. . . As far as sticking your appendage in and detecting the sweetness. . . I applaud you for returning to the simpler aspects of life. . . .

[brazilhead]

Sir Law, you´re on the right track investigating everything that could have gone wrong but on my first batch I had a 1.036 OG and the culprit turned out to be the grind. Did you grind it yourself? I was grinding based on pictures and written descriptions and I had the setting on my grinder way too coarse.

[Sir Law]

No, I had them grind it at the homebrew shop. I'm pretty sure that the problem was that on my first runoff, I didn't have a flat bed of grains. When I initially dumped the water in, I gave the grains a good stir and must not have evened out the bed. Also, as I was draining that one, I found that the SS hose braid was not lying on the bottom of the cooler, it was standing straight up through the grains about 1/3 of the way into the cooler. Those are 2 mistakes that are easily learned from and remedied, but I also want to take more precautions on my next batch to ensure that I'm hitting my target on all the steps. I do have promash, so that's how I knew my last batch was way low. I think on this next one I am going to test the runoff to make sure that getting in the ballpark. I appreciate all the help and if you have anything else, please toss it this way.

[Mill Rat]

I'm not a fan of the screen tube for the lauter tun runoff. Unless it's really long, it will leave grains with plenty of sugars in the far corners of your tun. It can also be easily crushed and even further limit the area of the mash tun from which most of the sugar is extracted. In your case, a screen that's bent upright is gonna really mess with your ability to extract sugars from any of the grain below the top of the screen. My preference is a false bottom, with a manifold sized to your mash tun bottom a close second. Of course, malt is rather cheap and an extra pound of malt will make up for a lot of lauter tun efficiency limitations.

[Mad Scientist]

Sir Law, I am sorry I did not respond to your PM....I was typing a response, and got up from my home machine, then my nephew closed the window to play a game....little turd....at any rate some of my observations:

Set your extraction efficey to 65% not 75%. While 75% (and beyond) is something to shoot for, I took me a while to get there once, and I hit to buy a mill and mill the grains myself to do it consistently.

When you buy grains form the lbhs, take a gap feeler gauge, and insist that they set the gap in front of you, that or buy grain form someplace else.

Instead of brown malt, use two row, brown as I recalled, does not have the diastolic power to convert as much other grain, and has a lower extract potential.

Also, as noted above, keep track of your sugars when you runoff. I watch my sugars when I do it, to make sure that I get more or less everything out of the grain. Just cheack overy few minutes, it does not have to be a continual monitoring...I might check may gravity during runoff 5 or 6 times.

That being said, what is your equipment set up? Also, what was your mash temp for the sweet stout?

[chapesh]

knowing your setup will help alot. the thing that seems glaringly obvious to me is the screen being positioned wrong, you would leave alot of sugar ing the corners, remember you want an even flow of sparge water over your grains, and even with that you will get "channeling" in the bed, water takes the path of least resistance, it will find it! so i will "cut" my grain bed during sparging. what that means is i take my paddle and actually cut into the grains, i will do this several times, in a different spot each time, also keep at least 1/4 of an inch of water on top of the grain bed during sparging. i have just begun this process for the last few brews and have been above my projected efficiency each time. now let me say this it takes time to learn your setup, you may not have the greatest efficiency. i didn't and it seemed to be several little things that were keeping mine down. the crush was one, controlling the sparge was another, and remember your water may change from month to month adding gypsum to my brews seems to have helped. also grain is cheap, set your efficiency lower and by more grain. also keep your sparge h2o above 168f. i actually start hotter than that 175ish. stay with it even a bad brew is good!happy brewing.

[Mad Scientist]

Originally posted by chapesh
....also keep your sparge h2o above 168f. i actually start hotter than that 175ish.....

Yeah, I start the sparge at about 175. But after it cools a bit, I do not heat it back up that high.

[BrewDog]

What they all said above is great stuff and right on target.
Another thing to pay attention to is your sparging rate (ie, how FAST you are sparging), especially for a braid. If you go too fast, the water has more of a tendency to channel. This is because the water pressure differences across the bed become greater. Near the braid, the pressure is low. That water is going away at a fast rate, so it is sucking more water in to replace it (nature hates a vacuum). The water away from the braid is stands still, and it never gets replaced by sparge water. It is kind of like layers of snow in an avalanche. The new lighter stuff on top glides right over the older heavier stuff on the bottom.

HTH-