Here is a period recipe for a spruce beer.
Take 7 Pounds of good spruce & boil it well till the bark peels off, then take the spruce out & put three Gallons of Molasses to the Liquor & and boil it again, scum it well as it boils, then take it out the kettle & put it into a cooler, boil the remained of the water sufficient for a Barrel of thirty Gallons, if the kettle is not large enough to boil it together, when milkwarm in the Cooler put a pint of Yest into it and mix well. Then put it into a Barrel and let it work for two or three days, keep filling it up as it works out. When done working, bung it up with a Tent Peg in the Barrel to give it vent every now and then. It may be used in up to two or three days after. If wanted to be bottled it should stand a fortnight in the Cask. It will keep a great while.
Source: Journal of General Jeffrey Amherst, Governor-General of British North America
Note that this beer did not use any form of barley malt and was composed entirely of molasses with spruce added for flavor.
If you want to get into period brewing, take a look at Raudins Publishing. They have a couple of brewing books dating to the 1760's
[url]
http://www.raudins.com/BrewBooks/[/url]
Here is a link to the pub a couple of us do at some of our Rev-War events.
http://64.41.64.113/tavern/
I hope to have a small(3 Gallon) period style system set up by the end of the year.