When it comes to the use of brewing terms from long ago my first stop for answers is Ron Pattinson's blog,
Shut Up About Barclay Perkins. Ron is a beer historian who uses brewery log books among other period documents in his research. I went to his blog and searched "dough-in" and found these... although he doesn't go into detail about the actual process of doughing-in there are clues in his mash step layout.
In a recipe Ron posted for a beer brewed in 1942 by Barclay Perkins that the brewery called "XLK" is listed the following:
Processes
Advanced Mash – Pretty much the same mash as the KK from last week (2011-03-02 – 1942 Barclay Perkins KK).
Dough-in, underlet infusion and then a sparge (165F/74C) that was usually quite long. The simple infusion produced an identical beer to this advanced mash in this instance. As always, you are left up to find the hot liquor temperature needed on your system to achieve the temperatures below.
Mash | ºF | ºC | Time |
Dough in | 147 | 64 | 30 |
Underlet | 152 | 67 | 90 |
A second recipe for another Barclay Perkins beer from 1928 identified in the brewery log as BBS Ex (Double Brown Stout) lists a similar step:
Processes
Advanced Mash – Similar for most of the bigger beers this one had a two step mash followed by an extended sparge. A simple
dough-in with a short rest and then an underlet to the final temp. The mash temps are pretty high for this beer which can go a long way to explaining the high finishing gravity here.
Mash | ºF | ºC | Time |
Dough in | 153 | 67 | 30 |
Underlet | 158 | 70 | 90 |
And yet a third Barclay Perkins recipe, this one from 1930 and the London brewery's foray into brewing lagers come this Dark Lager mash schedule:
Mashing: Now she starts getting a bit weird (vol/temp depend on your system).
Dough-in: Only the base malt is use.
Rest 1: 120F (49C) x 40min
Rest 2: Boiling liquor is added, as well as steam, to bring it up to 147F (64C). The crystal malt and roast malt is then added.
Rest 3: As soon as Rest 2 is mixed in, hot liquor is added to bring up to about 157F (69C). Rest 10 min.
Rest 4: Boiling liquor is added to bring to 168F (78C). Rest for 30 min.
Summary: Rest 1 (40min), Rest 2 (2 min), Rest 3 (10 min), Rest 4 (30min).
As you can see this is a really weird way to go about things. A normalish protein rest using only the base malt, then adding hot liquor to bring you up close to sack rest and loosen the mash to mix in your crystal/roast and then enough hot liquor to bring you up to a higher sacc rest. That rest is pretty short seeing that the mash was infused to sacc rest rather than steam heated and a pretty extended very high sacc rest. Then sparge away at 170.