Why do British sailors need special tea? It's not the start of a dad joke; the answer is based in science. The drinking water onboard a warship is different to your regular tap variety, and therefore results in a different brew that can affect the taste of a cuppa.
"Ships make their own water—they don't carry tanks of water around the place—and they use a process called reverse osmosis; they have RO plants on board," explained Andrew Gadsden, founder of All About Tea, in a phone call.
Gadsden was formerly an officer with the Royal Navy and with All About Tea based in the port city of Portsmouth, he thought the country's warships could use their own special blends. On Tuesday, Captain James Parkin tweeted a picture of tea designed for the HMS Bulwark.
Reverse osmosis is a purification method that involves pushing salt water through a semipermeable membrane to remove the salt. The end result is drinkable, but not necessarily the best for a brew.
"This produces a water which has very few minerals in it; it's very pure water, which means it's very soft water," said Gadsden.
Soft water doesn't contain many minerals, whereas hard water does. This varies around the country—if you see a lot of residue and soap scum around your taps, it's likely hard water. As a result, soft water is more acidic, and hard water more alkaline. It's this that affects tea brewing.
Soft, acidic water makes tea brew very quickly, so you might assume a ship's reverse osmosis plant is perfect for a cuppa. But Gadsden explained that the fast brewing process can draw out too much flavour from harsher blends. "That is why a ship is a very special situation for producing a tea blend," he said.
All About Tea's HMS Bulwark teabags contain a Ceylon, Assam, and African blend. The Ceylon, Gadsden said, is the key to a nicely flavoured soft water tea. "The African gives it lots of colour, which people like, and the Assam just gives a little bit of depth," he added.
Gadsden said he'd mainly been giving away the warship-themed teas as gifts to friends in the Navy and was applying to the Ministry of Defence to use the ship's badges.
"When you're away for months on end at sea, it's the little things that make a difference to your day," he said. "Standing on the bridge at 3 o'clock in the morning during the middle watch, a cup of tea makes all the difference, and if it's something that really tastes good—which, frankly, MOD-supplied tea doesn't—it's one of those little things that can make a huge difference."