In the medieval Europe of popular comic portrayal, everything is dirty and nothing is accurate. But real medieval Europe was obsessed with the regulation of weights and measurements. Almost everything was regulated, partly so that somebody could extract a fee from the process. Fees, tolls, fines and licenses: now we’re at the heart of the true medieval landscape.
Medieval commerce took place in towns that had been granted self-governing charters by the feudal lord. Both buyers and sellers in each town were fiercely jealous about false measurements that might cheat the buyer. While some sellers didn’t mind cheating, the other sellers and artisans in town did not want stories of being cheated to make the rounds by word of mouth. Even one false measure could lead to rumors that lasted for generations. So merchants and artisans policed commercial measurement strictly.
Guilds were the first line in enforcing accurate measurements. Each artisan was required to mark his products with his unique symbol (his trademark). If any consumer complained to the guild, they would know which artisan to prosecute. Guilds also carried out random inspections.
The coopers guild, like others, required every barrel to be branded with the cooper’s mark. Only guild-approved barrels could be used in trade there. Unmarked barrels were by definition illegal. Buckets and tubs were not as important in measurement terms, but they were also branded for other quality purposes.
Towns, too, regulated measurements. Town governments had central offices of weights and measures; in some places it became customary to give this job to an official’s widow. It was a genteel way of supporting herself, since she just needed to certify that a guild’s or merchant’s set of weights and measures was accurate to the town’s official set. As central governments grew during the period, one of the chief roles at the king’s palace was to choose a standard for weights and measures. The king’s officers carried out random inspections of town measurement standards, just as the town inspected the guilds and the guilds inspected the merchants.
Each region or country had a set of standard barrel sizes to measure liquids. The archaic words for barrels, which to us seem interchangeable, were actually measurement labels: barrels, hogsheads, kegs, butts, pipes, firkins, casks, tuns, and kilderkins. The volume of each might be slightly different in England and France, but differences like these were well known to international merchants. (Here are some modern barrel conventions, provided by Wikipedia.)
Each industry for producing drinks or other liquids had traditional barrel sizes. Ale was sold in 30-gallon barrels, but beer came in 36-gallon barrels. Sweet wine (often from the Mediterranean region) came in butts, which held 18.5 modern gallons. Wholesale wine often came in tuns, the largest barrel size. Coopers in regions that produced more wine than ale could specialize in tuns, while the coopers in hopped-ale regions (the Rhine Valley) could focus on 36-gallon kegs. Perhaps sweet wine came in smaller barrels partly due to its Mediterranean origin, since trees were generally smaller.
We know from village and county magistrate records that one of the most commonly prosecuted offenses in medieval England was using ale pitchers that were a little bit too small. Ale was sold out of private houses for most of this period, and it was harder to regulate. Local officials took complaints seriously; alewives were fined on almost a daily basis for claiming one volume while actually selling a smaller one. The simplest way to create this cheat was to get a local cooper to use fresh oak when making your gallons and firkins. They appeared to be certified and correct, but over the course of a year, the wood shrank and allowed the alewife to skim profits. Towns and guilds both made it illegal for coopers to use green wood.