Overfilling...

Image via Wikipedia

I've always been fascinated by the way that water 'sticks' to surfaces, causing nuisance phenomena like teapots that always dribble from the spout. But sometimes you can use the stickiness to your advantage...

I regularly fill the water container for our two cats. The design is quite smart in that it provides a constantly replenished supply, at least whilst there is water left. It is little more than an inverted plastic container in a dish, and atmospheric pressure (countering the partial vacuum in the container) stops the water overflowing.

Filling the container, clipping on the dish and inverting it over a sink gives a result which is less than perfect - the water from the container fills the dish (and some of it also tends to spill into the sink during the inverting process) and so the water container is about half empty. I've tried filling the sink and trying to fill the container under water, but the sink isn't big enough to do it properly, and this wastes lots of water.

Instead, I turn the assembled container and dish through 90 degrees, and dribbles the water into the container by letting the water stick to the dish. The container quickly fills up, and gradually bringing it back to the normal position fills the dish.

The end result is a container that is very nearly completely filled with water, and a very neat use for the stickiness of water!

CD Hub Failure Modes

Whilst I buy a lot of CDs, I've also gradually been seduced by the instant gratification of online purchase of individual tracks, even to the extent of buying MP3 format tracks instead of linear WAVs or AIFFs.

Buying CDs online is easy and fast, but has one major downside - the hub in the centre of the CD case. Most CD cases weren't designed to be exposed to the trials of being posted, and so many of my CD purchases arrive with damaged hubs. Two examples from today's batch of deliveries illustrate this very well.


The first is from a black plastic 'Digipak', where the CD hub and finger access areas are moulded as part of a single piece of plastic that is stuck onto a cardboard cover that bends round to surround the CD. This hub had lost all of the top teeth, and only had half remaining. Opening a shrink-wrapped CD to find a shower of teeth falling out is a depressing feeling.


The second is from a conventional clear plastic 'jewel case'. Severe forces during transit have reduced this hub to just two teeth, plus lots of casualties rattling around inside.


Exhibit three is different - a survivor from earlier... The temptation to type: 'and here's one I received earlier' is enormous. Some jewel cases have the teeth connected across the top, and this seems to provide more or less total protection against tooth loss. Or at least, from my own personal experience, I've never encountered any teething problems with these. Now I would love to be able to credit the manufacturer here, but I couldn't find any identification marks at all. But well done, wherever you are!