Hey you guys liked the 1.6g/mL for DME figure just fine when I used it here:
How Do you Make a Yeast Starter?
Also, 1 cup of water weighs 236.7g
1cup x 8oz/cup x 29.57mL/oz x 1g/mL = 236.7g
So you’re saying your cup of DME only weighs 2/3 as much as cup of water?
If I were you I’d take that DME back to the store and get a refund. :
A cup of DME does not weigh 378.5g(13.35oz!). You won’t convince anyone of that. Depending on brand and how you measure a cup, 4.5oz-6.5oz at the most.
Are you thinking of LME? Liquid Malt Extract? Dry malt extract is very light compared to water. as not particularly easy to measure by volume (fl oz) as the amount of moisture in the air will greatly affect the weight as will how tightly packed the cup is.
Fair enough, but that cup of DME is not full of 100% DME, it has quite a bit of air. A cup of DME measured from a bag of powdered DME will weigh about half of that.
OK - rule of thumb [u]1 lb of DME added to 1 gallon of water will give you a specific gravity of 1.045[/u]
1 lb DME = 1 lb
1 gal water = 8.34 lb
1 lb DME + 1gal water = 9.34 lb
9.34 lb / Vwort = 1.045 x (8.34 lb/gallon)
9.34 lb/ Vwort = 8.715 lb/gallon
9.34lb / (8.715 lb/gallon) = Vwort = 1.072 gallon
Vdme = Vwort - Vwater
Vdme = 1.072 gallon - 1.000 gallon = 0.072 gallon
density of DME = 1 lb / 0.072 gallons = 13.89 lb/gallon
(13.89 lb/gallon) x (1 gallon / 16cup ) x (16 wt.oz / 1 lb) = 13.89 wt.oz. / cup
Specific Gravity of DME = (13.89 lb/gallon) / (8.34lb/gallon) = 1.665
Recall - Specific gravity can be expressed as g/mL
therefore DME density = 1.665 g/mL
More dense than the 1.6 g/mL I used in my previous calculations
It’s a little early in the morning for me to follow math. But I can scoop a cup of DME out of the bag and put it on a scale. 185 grams. Munton’s Extra Light DME, full cup, packed down somewhat.
Actually, that isn’t quite right either. One pound of DME made into a solution with a total volume of one gallon will have an SG of around 1.045. You’re also assuming that the volume of the solution is equal to the sum of the volumes of the solute and solvent, which is a notoriously common fallacy in chemistry.
Using the density of a solid’s constituent particles introduces a lot of error when that solid is granular. The packing fraction will make a huge difference. The variation between sifted and packed flour, for example, is 25%: Wheat Flour - Kitchen Notes - Cooking For Engineers That’s why people are always encouraged to measure by mass rather than volume.
Notice that you’re saying a gallon of DME weighs about 14 lb. I’m sure you’ve seen a 5 lb bag of DME at a LHBS or elsewhere. Does it have a volume of 1/3 gal, or is it more like a gallon?
Alright.! Some of you are getting close.
A hint:
bulk density vs particle density…
Certainly not in my experience. I took a slurry out of the fridge yesterday and within 10 min. I pitched it, before it could warm up. I had fermentation going within 2 hours.
:
I’m no mathmagician or scientist, but you don’t need to be to figure out the DME volume and weight issue.
We’re still waiting on the cold pitching lag time theory…
Macros, micros and brewpubs are doing it and they have the most to lose if something goes wrong due to increased lag times.
I like to prepare starters with DME and water to a S.G.=1.020-1.030.
I use approximately .75lb DME to 1 gallon of water which will make approx 30GU’s or 1.030 after boiling for 10 min. This ratio of DME to water seems to give me the best results.
I then chill the starter wort down to the mid 60’s and pitch a vial, smack pack or about 2-3 Tbsp slurry and put on a stir plate for a few days. The starter wort is then cold crashed to drop out all of the yeast into a cake on the bottom of the flask or container.
When I’m ready to pitch the yeast into my beer wort, I’ll remove the starter from the refrigerator several hours prior to pitching and decant the spent wort and only pitch the yeast cake.
All this talk about starters and cold crashing brings up a question for me. If you are doing a starter for a hefeweizen wouldn’t cold crashing and decanting select for the more floculant yeasts? thus causing your hefe to be to clear? (mitout hefe instead of mit?)
Lobbying to be a moderator perhaps?
lol, no. It has never crossed my mind.
Are you seriously going to pretend that you’re trying to teach us something? :o ;D Admit it, you neglected to account for the air when you scoop a cup of DME! ;D
I don’t know what you mean by “getting close”, I said it:
Morticai said it:
Sean said it:
Do you have some magical phrase that you are looking for?
I don’t know…how about:
As porosity goes to 0, bulk density approaches particle density.
So BFI is the only one allowed to have fun sometimes?
You’re good with 1 cup DME to 4 cups water?
Never mind.
Oh man… you edited out the altruistic stuff.
No worries, I wasn’t offended.
;D That works. I don’t remember that phrase from any of my classes, but that could be because they were mechanical engineering or biochemistry classes, not civil engineering or materials science or soil or any of a host of things where that would come into play. It could also be because I wasn’t always paying that much attention 
Not at all, it’s just not always clear when people are having fun. ;) That’s one of the problems of the forum, and why I try to use emoticons so people know I’m not taking things too seriously ;D ;D ;D.
Nope, like I said, 1/2 cup DME to 4 cups of water is a better ratio for a starter IMO.
Ok, so I tossed the original starter and picked up 3 slap packs of Wyeast 1056 American Ale. (propagator packs, not activator packs) Mr Malty calls for a 3.26 liter starter using 2 of the 3 slap packs (I bought an extra to keep as insurance) and 326g DME, roughly 11.5oz if I did my math correctly. It recommends 1g DME per 10 ml final volume. The next problem is that my flask only hold 2000ml, yikes! Any recommendations for alternative vessels to prep my starter in, or should a 2000ml starter be sufficient?
It’s not a good idea to try and get the full 2L of starter in a 2L flask. Since it gets skinnier as it nears the top, you’re reducing the surface area through which oxygen gets exchanged and the whole point of a starter is to get plenty of oxygen to the yeast for growth.
For a bigger vessel, lots of folks use a 1 gallon glass juice/cider jug.