Hypotheical Partial Mash... OG too low how much Malt Extract to add?

[Babybatch]

Okay....

So I'm planning out my first brew ever. Rather than an extract I'd like to do a partial mash. One of the advantages that was mentioned was that if your OG was too low for your batch that you could add more ME to achieve your desired result.

So my question is: At what ratio should I add ME in such a case? Is this dependent on the ME being used? What would be a general rule?

And....

If the OG is too high... What do you do?

Ambitious newbies need you.

 

[ajf]

If you add DME, 1 lb yields 45 points per gallon.
If you add LME, 1 lb yields 36 points per gallon.
Mathematically, a point per gallon is the (SG -1) * 1000, so an SG of 1.040 gives 40 points per gallon, or an SG of 1.055 gives 55 points per gallon.
So if you start with a an OG of 1.040 (40 points per gallon) and you want an OG of 1.055 (55 points per gallon), you need to add 15 points per gallon, or 0.33 lb per gallon of DME or 0.42 lbs per gallon of LME
If you have a 5 gallon batch, multiply these values by 5, giving you 1.65 lbs DME or 2.10 lbs LME.
These figures are not completely accurate, as adding extract will increase the volume, but the difference caused by the volume increase is insignificant.
Ideally, you should calculate the shortage during the boil by measuring your pre-boil gravity, and forecasting your OG using the formula pre-boil gravity/pre-boil volume = OG/Post boil volume. This allows you to add the extract during the boil.
However, you need to cool the pre-boil sample to get an accurate gravity reading.

Hope this helps

-a.

 

[Babybatch]

If you add DME, 1 lb yields 45 points per gallon.
If you add LME, 1 lb yields 36 points per gallon.
Mathematically, a point per gallon is the (SG -1) * 1000, so an SG of 1.040 gives 40 points per gallon, or an SG of 1.055 gives 55 points per gallon.
So if you start with a an OG of 1.040 (40 points per gallon) and you want an OG of 1.055 (55 points per gallon), you need to add 15 points per gallon, or 0.33 lb per gallon of DME or 0.42 lbs per gallon of LME
If you have a 5 gallon batch, multiply these values by 5, giving you 1.65 lbs DME or 2.10 lbs LME.
These figures are not completely accurate, as adding extract will increase the volume, but the difference caused by the volume increase is insignificant.
Ideally, you should calculate the shortage during the boil by measuring your pre-boil gravity, and forecasting your OG using the formula pre-boil gravity/pre-boil volume = OG/Post boil volume. This allows you to add the extract during the boil.
However, you need to cool the pre-boil sample to get an accurate gravity reading.

Hope this helps

-a.

Yes that helps. Thank you. I guess I've still some learning to do here:

should calculate the shortage during the boil by measuring your pre-boil gravity, and forecasting your OG using the formula pre-boil gravity/pre-boil volume = OG/Post boil volume.

So let me see if I understand correctly:

"Pre-boil gravity"

If I was doing AG this would happen after mashing and before the boil.

In a PM would this happen after you mash and add your initial malt extract?

Or should this happen after you mash but before you add any ME?

Both seem to make sense in their own ways. (At least in my silly brain.)The later seems the more logical conclusion now that I have typed it out. It seems that the pre-boil gravity being taken after you mash but before you add ME would offer greater accuracy in that actual amount of ME that you will want to add. In turn a resulting OG that is closer to where you want to be with less fiddling post boil.

 

[ajf]

I agree with you. If you add some extract, and take a sample after that, you won't really know how much of that extract has been dissolved (if using DME), or how well it is mixed in with the wort (if using LME).
One other thing I should have said is to stir the wort really well before taking the sample, as without stirring, the wort will be extremely stratified with the high density first runnings at the bottom, and the low density final runnings at the top.

Good luck

-a