Converting recipe to partial mash

I printed Deathbrewer's treatise on partial mashing and want to give it a go with an American Pale Ale recipe from How To Brew.
That recipe calls for 3.3 lbs. LME at boil and 3.3 lbs. LME at knockout. Also included is a steep with .5 lbs. of 60L crystal malt.

The all-grain version calls for 7 lbs. of British pale ale malt, .5 lbs. of 60L crystal, .5 lbs of amber malt and .5 lbs. of munich malt.

If I wanted to do a partial mash, is it correct to assume that I would mash half of the British along with all of the crystal, amber and munich and use half of the LME?

Hand-holding is most welcome. I brewed my first batch in many years earlier this summer so the skills are quite rusty.

First you need to calculate how much grain you can handle mashing using your equipment - the more grain, the cheaper your batch will be, and the closer to all-grain the flavor will be. Simply plug your specialty grains and however much base malt you can handle into some brewing software; then add malt extract until you reach your desired original gravity in the software. That way, you you optimize partial mash recipes for your equipment instead of following some recipe that may use way more extract than you need.

Then, you mash all of the base malts along with all of your crystal/roasted malts (i.e. what extract brewers call "steeping grains"), run off and sparge. You don't add any malt extract to the mash - it'll not do you any good in there.

To add to what ArcaneXor said, I generally start with the AG recipe if it's a available - use all the specialty grains and adjuncts plus as much base malt as possible (up to the maximum you can mash using your system and method). Whatever base malt is left over that doesn't fit in the mash, convert to extract using the ratio of 1 lb grain = .75 lb LME = .6 lb DME. Try to use at least as much base malt as the total of specialty malts. For example (using the recipe you gave), shooting for a 4 lb grain mash:

.5 lb 60L
.5 lb amber malt
.5 lb munich malt
2.5 lb British pale (maris otter)

The remaining 4.5 lb of pale malt would become 3.4 lbs of light LME (1 can is close enough but bulk LME is better IMO) or 2.7 lbs of light DME, added in the last 10 minutes or at knockout.

You also need to anticipate water volume - I do the mash with 1.25 quarts of water per lb of grain, then sparge with enough to fill my pot or twice the mash volume amount, whichever I reach first. The grain will absorb a quart or so as well, so for my 3 gallon pot I would mash with 5 quarts and sparge with about 8 quarts. Combine mash and sparge runnings and start the boil, adding hops per schedule. Add the extract in the last 10 minutes, cool and top-up to recipe size.

If I wanted to do a partial mash, is it correct to assume that I would mash half of the British along with all of the crystal, amber and munich and use half of the LME?

Click to expand...

That would work just fine. It doesn't have to be complicated and if your LME is in 1.5 kg cans, why worry?