A firkin is a wooden tub that butter producers used to ship their butter in.
Essentially a small barrel with straight as opposed to convex sides, they were made by barrel makers.
Made by barrel makers, they were essentially a small barrel with straight as opposed to convex sides, though generally they were a little bit wider at the bottom than at their mouths. There was no standard height, but a non-untypical size would have been 18 cm (7 inches) tall, and 15 to 18 cm (6 to 7 inches) wide. As there was no law governing the size of butter firkins, the volume that a firkin could hold had no particular relationship to the measurement called a “firkin.”
There would be a handle, made of wood or wire, to allow easy carrying. The outside of the firkin was sometimes painted.
Firkins were generally soaked in salt water before they were used, then rinsed out twice with fresh water.
The butter needed to be packed in as tightly as possible to eliminate air spaces, which could cause more rapid deterioration of the product. To cover the butter, a bit of brine was spread on top, then a cloth smoothed on to stick to the butter, then a thin paste of salt rubbed over the cloth to seal it. Once the butter reached the store or market stall, you peeled the cloth off to serve your customers.
Despite the covering precautions, firkins weren’t a great way to ship butter. They weren’t air tight by any means, and mould could get in. Even if it didn’t, the taste of the butter could go off from taking on the flavour of the wood.
In Ireland, people used to bury butter in firkins in peat bogs. This both protected it from robbers, and allowed it to ripen and take on a strong flavour. The acidic environment of peat bog would contribute to the preservation of the butter. This practice was done as late as the early 1700s, and was also practised somewhat in Iceland, Scotland and Sweden.
In America, by the mid 1800s, shippers began to prefer larger tubs.