DME in Patial Mash question

[drunami]

Hey all,

I've done about 25 specialty grain/extract brews and am plotting a move to partial mash (no space for full-on AG) My question is the following:

Does anyone have an accurate way of measuring the gravity of DME?

I use Breiss pilsen or extra light for my extract (to sub for missing base grains) and I'll need to continue to do that with partial mash so I can hit my OG. However, it seems like every time I calculate how much DME I need, I'm way off (last week I brewed an ordinary bitter, calculated to hit 1.050, and OG was 1.063). I'm not consistently overshoot or undershooting, it seems to go both ways. I've checked the calibration on my hydrometer -- no problems there. The published specs for breiss products seem to be well below what I actually get. In my previous apartment, I had room to buy a huge bag of DME, and so I could measure the gravity of 1 lb/gal and go from there. Now I don't have that kind of storage space, so I need to buy in smaller quantities, but it seems like maybe each bag is a different efficiency?

Anyway, my move to partial-mash is dictated largely on wanting to get a bit more control over my grain bill. Unfortunately, without sorting this issue out, I'm still going to be shooting blind a lot of the time.

Anyone else have these issues before? How'd you solve em?

Thanks in advance,
Dru

 

[doug293cz]

DME potential should be well controlled by the manufacturer, so the variability is most likely in your process. Are you measuring the DME by weight or volume? You can't be accurate unless you measure by weight, as density can be quite variable.

The SG contribution of the mini-mashes can be quite variable if your process is not tightly controlled. Do you measure the SG and volume of the wort prior to adding DME, and adjust the weight of DME used based on those measurements?

Pre-boil measurements, or measurements immediately after adding DME, can be highly variable due to incomplete mixing. When are you taking your SG measurements?

Brew on

 

[drunami]

To be clear, I haven't done any mini-mash yet. I know it gets more complicated, which is why I'm trying to get this inconsistency locked down before I add more variables to the equation.

As for extract brews, my method has been this:

1. steep specialty (usually in about 3 gal).
2. After steep, boil, do hop additions, etc.
3. at 15 min out add calculated DME - measured by weight
4. after boil, chill, add to primary, fill up primary with bottled water to get 5 gal.
5. take gravity reading right before pitching yeast.

Is there anything in that method that could be the problem? I don't think so. Also, as I mentioned, when I was able to buy DME in bulk I was able to get consistent results throughout the life of the bag, once I figured out its strength.

 

[doug293cz]

To be clear, I haven't done any mini-mash yet. I know it gets more complicated, which is why I'm trying to get this inconsistency locked down before I add more variables to the equation.

As for extract brews, my method has been this:

1. steep specialty (usually in about 3 gal).
2. After steep, boil, do hop additions, etc.
3. at 15 min out add calculated DME - measured by weight
4. after boil, chill, add to primary, fill up primary with bottled water to get 5 gal.
5. take gravity reading right before pitching yeast.

Is there anything in that method that could be the problem? I don't think so. Also, as I mentioned, when I was able to buy DME in bulk I was able to get consistent results throughout the life of the bag, once I figured out its strength.

Yep, step 4. It is actually quite difficult to get a good SG reading after adding top up water to the fermenter. It takes much more aggressive mixing than most people realize to eliminate the density gradients under those conditions. Get yourself a plastic paint stirrer (drill attachment), and get a good vortex going in the fermenter for about a minute. This will also help aerate the wort, which is good for yeast health (but only prior to the start of fermentation.)

Brew on

 

[drunami]

Huh. I've never thought about that.

As for solutions, I don't own a drill -- and as I live in a tiny NYC apt I'm not getting one any time soon. Anyone else have any ideas for better integration?

Alternately, maybe I could just start taking gravity readings of the concentrated wort after chilling before diluting?

 

[doug293cz]

...

Alternately, maybe I could just start taking gravity readings of the concentrated wort after chilling before diluting?

That will work.

OG = 1 + [(Post-Boil SG - 1) * Post-Boil Volume / Diluted Volume]​

Brew on

 

[drunami]

Sweet. Thanks for all the help.

Relating to both wort mixing and oxygenation, has anyone tried using an immersion blend (aka stick blender) to do the job? The model I have is small, but so long as I don't break the surface with it running, it should basically do what a paint stirrer does right?

 

[drunami]

Just a quick update:

1. Tried the stick blender to aerate the wort, a whisk will probably be better and easier to clean.
2. Brewed a Saison this weekend as my first partial mash. Took a grav reading of the post mash wort, calculated my required extract, took a reading before diluting the wort, and then once everything was in the fermenter. Shooting for a target OG of 1.050, I got 1.052 by calculating from the concentrated wort, and 1.049 from the diluted final volume! I'm quite happy with that.

Thanks again for all the help doug.