Clonebrews Partial Mash Confusion

[RyanGT]

Hey everyone! First post! Been brewing for a few years and am stumped on what to do here. I hope someone can help.

I really wanna do a recipe out of the Szamatulski's Clonebrew's Vol. 2. book, the Watney's Cream Stout, using a partial mash method, but the math doesn't seem to work out.

Here's the extract recipe:

12 oz. 55L Bristish Crystal
12 oz. Bristish Chocolate
4 oz. Flaked Barley
4 oz. Roasted Barley

5 lbs. Munton's light DME
10.6 oz. Malto Dextrin
1.4 oz. Fuggles

The partial mash calls for 1.5 lbs. British 2-row pale malf with specialty grains for 90 min and says to omit 2 lbs. DME... huh? Ok, this doesn't make sense. From my calculations, I think it should be like 2.9 lbs. pale malt.

So am I right to question this? Do the speciality malts add extra fermentables with the 90 minute mash?

Thanks for any help. I really want to make this.

 

[WVbrewer]

I did a couple partial mashes form clone brews a few years back and found my OG was indeed lower than expected. I'd follow your instincts here and either add more 2-row, or have some dme on hand to compensate. Check your gravity pre-boil and do the math to see if you will hit your intended gravity number. Oh...and to answer your question.....specialty grains mashed will not significantly add extra fermentables. Your base malts do the bulk of that.

 

[ajf]

I agree with you that 2 lbs DME is roughly equivalent to 3 lbs pale malt.
You will probably extract a little more from the specialty malts during a 90 minute mash than you would during a steep, but the difference would be pretty small. The pale malt would be able to convert the starches in the flaked barley, but with only 4 oz of flaked barley, the difference will be insignificant.

-a.