Rough Lumber for the Ofuro
In order to explain how the Ofuro works (whoever thought of a bathtub made of wood?) I think the best way to do it is to go through, step by step, how I make them and the decisions involved.
The first step is, of course, finding partnerships with local arborists, forest managers, millers and sawyers, for a number of reasons. One, I’m working with fairly rare material, and one that I want to ensure is harvested in a sustainable way. Luckily, in California, Redwoods are very much protected. Since old growth redwoods can’t be cut down, in this case, I found someone who specializes in both antique and what are called ‘virgin buckskin’ trees - or trees that fell on their own, at the end of their long life. This ensures the wood is harvested in an ethical and sustainable manner.
Antique redwood is a great way to go, and the other option. This is wood that has been taken out of old buildings, water towers, flooring, and more - so not only is it sustainable, as no new material is harvested from nature to use it, but it’s a way to access this kind of wood without going into a forest at all. It’s like a time capsule to 1850, when they were first putting up these buildings. The only problem is, they are generally filled with nail holes and such, that doesn’t let water in. So a virgin buckskin is really the way to go.
But why old growth in the first place? Well, Redwood trees (like all trees) grow in cycles - the winter and the summer. This is where the ‘Rings’ in a tree that everyone knows about come from. The harder, darker rings are from the winter, when a tree goes dormant and doesn’t grow much, and the softer part is from the summer months, when it’s soaking up the sun and making it’s move.
The average 4x4 fencepost you can buy at a Home Depot in California is probably redwood from a tree that is only about 3 or 4 years old. That’s great for a fencepost, which can be rougher, will be exposed to the elements, and that you need a lot of. But for something like an Ofuro soaking tub, I have to get a little pickier. I’ve counted the rings along the pieces of the bottom of one of my Ofuro’s, and a single panel can have over 1500 years of rings across it.
Wood expands and contracts with moisture. This is why doors stick in the summer, when they swell and the air is thick with humidity, and this is why drawers fall out of cabinets more easily in the winter, when the wood shrinks. So how do you make something out of wood that’s intended to be filled with water, in a humid bathroom, without the tub springing a leak?
You start by finding wood that will expand and contract the least - old growth redwood, you can find the numbers from the US forestry department. A three inch wide board of old growth redwood will expand and contract less than one thousandth of an inch in normal humidity changes, and the more rings the better. I get it professionally dried, by kiln drying it, it shrinks down as far as it will go, which is really the problem. If it shrinks too far, the wood will have cracks open up and let water through. Redwood is also stiff, but flexible. This makes it great for handling the hundreds of pounds of pressure against the walls.
By choosing wood that has a tight grain, is stable, is water and rot resistant, and handling it with care throughout the process, you can have a tub that will last the rest of your life with barely any maintenance. By keeping them filled with water, you never let it dry out enough for a crack to form.
There is more than goes into keep the water in a tub, which I’ll get into at later points. But the use of old growth redwood isn’t exotic for the sake of luxury - it’s the ideal material for a wonderful ritual bath.
