My husband went to the local hardware store the other day. What’s so exciting about that? You’ve obviously never been to a hardware store in Japan.

Though we have the same experience every time we go, I’ll use the most recent one as an example. He bought a can of varnish. A can of 0.7 liters of it. No, he couldn’t buy 0.5 or 1 liter, only 0.7 liters. Perhaps the reason they sell it in this quantity is because 0.7 is just enough varnish for a 3-mat tatami room, or about 4-5 square meters. OK, all good.

If you buy 0.7 liters of varnish, you’d expect it to come in a 0.7-liter can, right? It doesn’t! The can could hold much more, but doesn’t because you only bought 0.7 liters worth. What? Uh-huh. You get a can that holds 1 liter of paint or varnish, but only has 0.7 liters in it, with no option to choose how much you actually want in it.

When I opened the can the first time I thought, Hmmm, this can is only half-full. Maybe the varnish has “settled” during shipping. Or perhaps, because it’s “varnish” and the Japanese don’t have the “r” sound in Japanese, the meaning has become “vanish.”

You could surmise that the Japanese varnish company is just being nice, giving you extra room to add thinner. But still, 30 percent thinner would be too much.

Looking at the half-empty (or half-full) can might prompt one to say, what a waste! But not so fast. How much of the can have they really wasted?

First, let’s measure the can to find out its area and potential volume. The diameter of the can is 108 mm. The formula for finding the area of a circle, which I’m sure you remember from high school, is π r². Or π multiplied by the radius². The radius of the can is r = 54 mm, so r² 2,916. Multiply that by pi, which is 3.14 and you get 9,156 mm². Multiply that by the depth of the can which is 108 mm, (9,156 x 108) 988,848 cubic mm, or basically 1 liter in volume. But in a 1-liter can we only get 0.7 liters. What a 30 percent waste!

The can can hold 1 liter, but since two positives (can can) equal a negative (can’t), it just ain’t gonna work.

So why don’t they offer full cans of paint in Japan? My guess is because in Japan they don’t use ovens, so can’t make pi. It’s just my guess, anyway.

When we buy boat paint, however, it is not sold by volume but by weight, in either 2-kilo or 4-kilo cans. You could fit much more into each can, but why would you want to do that? Especially when you can get people to buy half-full cans.

Perhaps the reason some paint is sold by weight rather than liters is that this way you can buy diet paint. I mean really, who wants fat paint? The slim and shimmery stuff with fewer calories is bound to look better on the wall, especially if it’s in a large room.

Or maybe when they say “kilos” they don’t mean 2 kg of paint, but 2 km? A can of paint will allow you to paint a line 2 km long.

There is nothing inherently wrong with selling paint by weight. It’s just takes some time to get used to it. Besides, it’s good to think outside of the box. Or can. But why stop there?

Consider, for example, if noodles were sold not by weight but by distance instead. Wouldn’t it be great to go into a noodle shop and say, “I’d like 10 km of noodles,” or, “I’d like noodles with a length that is the distance between Osaka and Tokyo.” You could even use a “nobori-kudari” noodle system. The seller would ask, “Would you like nobori noodles stretching to Tokyo? Or kudari noodles stretching from Tokyo?”

Another way paint is sold in my country is by its “flow rate,” which is a measure of viscosity. Paint is poured into a funnel and the rate at which it flows through the funnel is measured to give the flow rate. You need better flow rates to use a paint gun, for example in order to spray paint onto a surface.

Certainly we could apply the flow rate to other things in Japan. English fluency comes to mind. The trouble with English as a second language tests such as TOEIC and STEP is that they have a hard time testing English conversation fluency. A flow rate would judge students on the fluidity of their English as it flows out of their mouths. Smoother English would yield a better flow rate.

Wanting to get to the bottom of why there is so much wasted space in paint cans, I called up my friend Maekawa-san, who is a professional painter. He told me that paint cans are based on the weight measurement of water. A 2-kilo paint can holds 2 kilos of water. Since paints have different weights depending on their viscosity, the type of paint and its weight determines how much paint goes into each can.

When I asked him why they didn’t just sell paint by the weight of a full can instead, he gave the answer that you’ll find almost anywhere in Japan for anything — “Because that’s the way it has always been done.”

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