Allagash Brewing Co. is expanding in every way imaginable, except one. The brewery in a Portland industrial park off outer Forest Avenue has undertaken several construction projects this winter to boost brewing capacity and its lineup of beer and is expanding up to 41 employees.

However, “we have not expanded our distribution for several years,” brewmaster Jason Perkins said last week as he took me on a tour of the plant. “We’ve actually retracted from some.”

Allagash is selling as much beer as it can brew, and thus all the construction — so it can meet the demand. The brewery mixes its ingredients for its regular-line beers in 30 barrel batches, although it has tanks on site in multiples of 30 up to 240 barrels.

One addition that has helped improve capacity is a 30-barrel hot-storage container where a batch of wort (beer in the making) can be stored while another batch is boiled.

The most visible addition from the outside is a huge concrete bunker with four 240-barrel tanks sitting on top of it. The brewers can control the action in the tanks with controls in the bunker at the bottom, but by having the tanks outside, it allows workers more freedom to move inside the building.

The bunker was designed so two more of the tanks can be added when business warrants, Perkins said. As of now, Allagash brews about 25,000 gallons — about 800 barrels — of beer a week.

Allagash also will be adding a new bottling line this year. Its bottling system handles both its 12-ounce bottles and 750-milliliter cork and cage bottles. The 375-milliliter (12.7 ounce) bottles used for the limited-release beers sold only at the brewery are bottled by hand.

This is all a big jump from 1995, when Rob Tod began brewing Allagash White, an American version of a Belgian witbier with orange and coriander. At the time, very few American brewers were doing this. Partly because of Allagash’s success, they are everywhere now.

“It makes up about 60 percent of our volume,” Perkins said of the White. “That’s partly because it is only 5 percent alcohol, so people can have two or three of them, compared to Curieux at 11 percent.”

The new bottling line will help bring one immediate change: Sometime this year, Allagash Black swill join the White, Dubbel and Tripel and be bottled in 12-ounce bottles, as well as in 750-milliliter bottles and on draft.

The Black is my favorite commonly available Allagash, so this will mean that when I am by myself and feel like one glass of Black, I won’t have to worry about what to do with the rest of the bottle.

As I was leaving after Perkins had gone back to work, Dee Dee Germain — who does marketing and communications as well as some brewing — said she did a blind tasting of the Black, and she really liked it quite a bit.

I was a bit surprised, and asked if it wouldn’t be the same as the Black in the 750-milliliter bottle. Germain said there are significant differences, including that the cork and cage system can stand more pressure and can be more highly carbonated. So I am looking forward to tasting the 12-ounce Black.

The highlight of my tour was a visit to the coolship, a screened, unheated room attached to the brewery where beer is spontaneously fermented with yeast naturally occurring in the air, similar to the style of Belgian lambics.

Because brewing requires specific temperatures, the coolship — which has stained-glass windows and a door from an old church on Munjoy Hill to add an old European look — can be used only in March and November to early December. And Portland’s air has some of the same Brettanomyces and lactobacillus yeast found near Brussels that make lambic.

“We do not call our beers lambic because in the same way that Champagne can only come from Champagne, lambics have to come from Belgium,” Perkins said. “But our beers are very close.”

I joked that, with Geary’s being located in the same industrial park and Portland having several breweries using Ringwood yeast, the beers could have Ringwood in the mix.

Perkins said he hasn’t detected any, but they have sent samples to be tested to the University of California at Davis, which is noted for its wine school but also does programs in beer. They don’t have the results yet.

When we went to the barrel room for some tasting, two of the beers we tasted were spontaneously brewed.

The latest batch of Coolship Resurgam will be released sometime next month and sold only at the brewery. This is a blend of different batches from the coolship and tastes a lot like an old gueuze, with an absolute dry finish and a wonderfully sour complexity.

I mentioned to Perkins that I thought it had a bit of the flavor of cider left to go hard naturally, and he said the same yeast that gets into the apples probably gets into the beer.

A similar beer, Ghoulship, included fresh pumpkin, roasted pumpkin seed and molasses. I fear pumpkin in beer, but this was very good, with the molasses coming through strongly and the pumpkin in the background, but no pumpkin spices.

Mattina Rossa is not a coolship beer, but it is absolutely heavenly. It was brewed with 440 pounds of fresh local raspberries and had 100 pounds of raspberries added to the mix after a year of aging. This beer was nicely dry but still had a wonderful flavor of fresh raspberries.

I mentioned to Perkins that with the cost of the ingredients, the labor and space taken for aging the beers, they must be expensive to make.

“Say we charge $15 a bottle. There is no way of figuring it out, with the cost of this room and everything, but we are probably losing money,” he said. “But it is what we as brewers love to do: experimenting and making new beer. And our customers want us to do this.”

I also got to taste the new honey beer, Saison Mihm (the planned name, Saison Genever, was rejected by government officials). It is another very dry beer, with juniper berries the dominant flavor and the honey in the background. This beer will be available sometime this month, and it will be on draft only.

Allagash conducts tours of the brewery three times a day, Monday through Friday, adding Saturdays in the summer. If you would like to take one, go to allagash.com and click on “contact us” at the bottom of the home page and then “brewery tours.”

Tom Atwell is a Cape Elizabeth freelance writer. He can be contacted at 767-2297 or at:

tomatwell@me.com