DME volume addition question

[Hoochin'Fool]

Has anyone ever measured the actual volume change of: 1 gallon water after adding X lbs dme (thoroughly dissolved)?

From this weekend's goof, I think it must have been that 3lbs of DME dissolved into 3 gallons of RO water gave me a starting boil volume of about 3.4 gallons, and my post-boil OG being 10 points lower than intended. (I was targeting 3 gallons in the boil, and 2.5 gallons post-boil).

 

[VikeMan]

Sugar adds about 0.074 gallons of volume per pound added. So, 3 lbs. of sugar would add about 0.222 gallons.

Many years ago, I measured the volume increase for DME at about 0.064 gallons per pound. BrewCipher has used the result ever since, and I haven't had any extract brewers say that it has led them astray. Using that number, I'd expect a gain of about 0.19 gallons for your 3 lb of DME.

So I feel pretty confident that the impact to your volume was probably in the vicinity of 0.2-ish gallons for your wort.

I don't know how Beer Smith and others do DME volume calcs, but you might want to run your recipe through something and see what it thinks.

What was your exact measured volume and gravity, at what temperature was it measured, and how (hydometer or refractometer)?

 

[Hoochin'Fool]

Thanks VikeMan, I trust your .2 gallons for the DME volume contribution. I reckon that, plus my keeping the lid partially/mostly on because my crappy stove was really struggling to keep a boil going, is what led to my extra volume into the fermenter.

I've only got lines marking off each gallon on my bucket, so I was just eyeballing it to about 2.8 or 2.9 -ish gallons. (Tho when I changed my recipe in software from 2.5 gallons to 2.9 gallons, the predicted OG became 1.047, which is exactly what my hydrometer read @ 70F).

Lessons learned:
1) Don't try to boil more than 2 gallons on my crappy stove!
2) Keep the lid off
3) Undershoot final volume and use cold top-off water to hit target volume

 

[VikeMan]

1) Don't try to boil more than 2 gallons on my crappy stove!

If you can't (or don't want to) boil outdoors (propane), another option is to split a batch between two kettles, using two burners.

2) Keep the lid off

The lid should be off (or mostly off) to allow DMS to escape. But I wouldn't use final wort volume as the decision point for what to do with the lid. Whatever your process, figure out how much water you are boiling off and tell your brewing software what that rate is. It should adjust your total (pre-boil) water volume automatically. If it doesn't, find other software.

3) Undershoot final volume and use cold top-off water to hit target volume

Using less water in the boil and topping off isn't ideal, because it reduces hop utilization and increases maillard reactions (darkening the wort). It's better to figure out how much water you really need in the boil and use it.