From Loretta:
As you have now discovered, the Wenches can go on and on indefinitely about a subject, like refrigeration. We could probably do 50 blogs on food alone. In talking about refrigeration---and how I so don’t wish I lived in the early 19th century (except for the corset part, which is fine with me)--I mentioned my interest in dairies. Other of the Wenches encouraged me to hold forth, nerd-like, on the subject. (We do love to talk about our research, only a fraction of which appears into our books. Please let us know if you’d like more of this sort of thing occasionally.)
One of the love scenes in my new book, NOT QUITE A LADY, takes place in a dairy.
What image does that conjure in your mind?
Do you see a line of cows in a building, attached to tubes that are in turn attached to machines?
Do you see the place where you can go to get an ice cream cone made with actual cream from the actual cows in the adjoining pasture? (We’ve got one of those nearby.)
Do you see bottles of milk moving along a conveyor belt? I have a vague recollection of visiting a dairy farm on an elementary school field trip. I think there were bottles on a conveyor belt. Or was that the field trip to the Coca-Cola™ bottling plant?
Or are you remembering that, since my books are Regency-era historicals, my scene must be set in the early 19th century? Which means we must forget about the machines and tubes. Instead perhaps you see cows in a shed, and a woman milking them. 
My couple do not get smoochy in one of these places. They are at a neglected but extensive estate in Cheshire, and my heroine has restored the dairy, making it a thing of beauty. In fact, dairies on great estates were often things of beauty. Here’s one--the picture at the top of the strip, the Tower of the Four Winds at Shugborough: http://www.shugborough.org.uk/AcademyGreekPt1-177
I constructed mine from assorted dairies, especially those described in Christina Hardyment’s BEHIND THE SCENES: Domestic Arrangements in Historic Houses. For most of what follows, I am indebted to this book--and highly recommend it to anyone interested in what servants did to keep the big house running.
Though I combined features of several dairies for my fictional one, it’s most like the one at Uppark in Sussex, an 18th C dairy that Humphry Repton redesigned between 1810 and 1812.
(From NOT QUITE A LADY) “He stood in an airy and elegant room. A yellow and green flower design bordered sparkling white tile walls. A checkerboard of black and white marble covered the floor. Light filtered through stained glass windows whose design and color complemented the tiles’ flowers. A broad marble shelf ran round the room. A square table with a matching marble top stood in the center.”
Photo by Peter Glass: http://ourpasthistory.com/Gallery/uppark/Uppark0008
As Jo mentioned about larders, marble is good for keeping things cool. Some of the dairies had slate shelves with marble trimming. At Dunham Massey in Cheshire, there were slate sinks holding cold water to keep things cool.
Design and location aimed at keeping the interior at a cool, stable temperature (a writer later in the 19th C specified 55-60°F). The building ought to be sheltered from cold in winter and from heat in summer. Notice how sheltered and well-insulated Uppark’s dairy appears.
http://hex.oucs.ox.ac.uk/~rejs/photos/A40/Uppark/
Photo by Robin Stevens
As early as the 18th century, educated people understood the need for hygiene in milk handling. Every square inch of the dairy must be absolutely clean, including floor, ceiling, and walls. This is another good reason for stone and tile interiors. It’s also a reason for the lord and lady of the house to become involved: he perhaps in designing the structure according to the latest principles and she in supervising operations. 
It helped that this was a time, too, when a romantic view of nature prevailed. Marie Antoinette had a dairy to play in at Le Petit Trianon. It wasn’t heavy work.. Someone else milked the cows and carried the milk from the cows to the dairy. The person doing the carrying did not usually have a long walk, because people believed that the shorter the distance the milk traveled from cow to setting dish, the better the cream. (Photo of Uppark Dairy by James Stringer http://www.worldisround.com/articles/12208/photo10.html?photosize=small)
Our lady of the house would probably watch a muscled dairy maid pour the milk into shallow settling pans made of brass and copper, where it would sit for 24 hours (longer in winter). Then the maid (or perhaps the mistress) would skim off the cream with brass skimmers and small wooden skimming dishes. Some of the cream might go for household use. Or it might be sold, because not everyone had a dairy, even in the country. If cream was to be made into butter, they’d leave it to ripen for a couple of days. Then it went into the dairy scullery--a completely different environment--to be made into butter.
“I’ve had your dairy scullery scoured, too. As you can see, there is no door to it from here.” She gave a sweep of her hand to indicate the walls about them. “There will be no danger, therefore, of the scullery’s heat and steam leaking into this room and spoiling the milk. You will be relieved, I’m sure, to learn that most of the equipment is in good order. You will need to replace the wooden gutters but the vats and churn and coppers and such need only minor repairs. By the time you have acquired the cows you need, we shall be ready for the dairymaids to commence their work.”
Photo by Peter Glass: http://ourpasthistory.com/Gallery/uppark/Uppark0007
Later, my hero takes a look at the dairy scullery. (This is one of the bits I decided to cut from NQAL.) “The dairy scullery was where the heavy work went on. With its plastered walls, plain stone floor, and homely equipment, it was more workaday than the elegant dairy room. He would need to buy new utensils. The churns and such needed repair, as she’d said. But so far as he could see, the only major item he must replace was the rotted wooden gutter for carrying water directly from the pump into the copper where it would be heated.”
In the scullery, the dairymaid put the ripened cream into a churn (the barrel-shaped object in the scullery photos--the second scullery photo is by James Stringer http://www.worldisround.com/articles/12208/photo11.html). 
Once it reached the right consistency, she washed it. Then it went into the butter-worker--the rectangular tray on legs to the left of the churn. She rolled the fluted wooden roller over the butter, squeezing in salt (if desired) and squeezing out water, which drained out of a small hole into a bucket at the front. Getting the liquid out was quite a job, it seems. The dairy maid would dab at the butter with muslin to get the last drops out. Then she’d scoop out the butter with wooden butter-workers--wooden paddles--and pat it into shape. Human hands must never touch the butter while it’s being made.
The dairy scullery is where the dairymaids did all that crucial scrubbing and scalding. Here, too, is where they heated the milk they were going to make into cheese. And it’s where they made their breakfast.
Not every house had a dairy scullery. In those cases, the work was done in the kitchen scullery. I imagine that was not convenient, and not fun for the dairymaids, who were otherwise separate from the other household staff, and probably accustomed to more independence.
Apparently dairymaids were hot stuff in this era.
There’s a Rowlandson print of Dr. Syntax flirting with a dairymaid. At Uppark, in 1825, Sir Harry Fetherstonhaugh (pronounced Fanshaw), age 71, married his 21-year-old dairymaid Mary Ann Bullock. The marriage lasted 20 years. Sir Harry was 92 when he died, and I’m guessing he died happy.