For a late night summer party, we wanted to deploy an array of maybe 20 or so little LED garden lights along the periphery of our back yard. And since it was for a one-time event, there wasn't much sense in buying (or building) a set of nice looking permanent solar lights. So here is an alternative: make your own ultra-low cost temporary garden lights using LEDs, lithium coin cells, and mason jars.

To start with, we need LEDs and lithium coin cells. One each per jar. The best kind of LED for this design is an ultrabright LED with a diffused lens so that the light cast by the LED chip goes in *every direction,* not just in the direction that the LED points (which is what you get with LEDs that have clear lenses). Having easy access, we opted for the 10 mm diffused white LEDs from here, but you can get similar LEDs elsewhere as well.

For batteries, a very good option is Digi-Key. You *may* be able to do better from various eBay sellers and so forth, but we've gotten burned (figuratively, not literally) by bad sets of lithium coin cells, so beware! One thing to keep in mind: there are strict restrictions on shipping lithium coin cells by air, so if at all possible, allow time for ground shipment of batteries. (And, if you have leftover coin cells, you can always use them to make BristleBots!)

Next, you'll need some jars.

Mason jars are available by the dozen in your local supermarket, in the canning/pickling section (which seems to actually still exist!), but are also available online of course. The "other" way is to start with a set of recycled jars, of course. If you eat a lot of pasta sauce from jars, you can build up a collection pretty quickly. And even if you don't eat food that comes in jars, you can usually find good jars at thrift stores-- so you really don't need to spend a lot on this. But even if you're buying brand new jars, you should be able to get all of your parts for a grand total of about $1-$1.50 per light jar.

(If you want to get a bit fancier, there is also plenty of room for that. I like this set of instructions for making frosted glass jars for LEDs-- those would work well for this project too.)

Now we hook up the LED to the battery as though we were making LED Throwies. *

Connect an LED directly across the terminals of the lithium coin cell. The long lead goes to the '+' side of the battery. Wrap it once with tape-- just about any kind-- to keep the LED leads touching the battery cell. (We had blue masking tape handy so we used that-- it seemed to work just fine.)

*Important safety tip: do not throw the completed LED jar lights.

Now the tricky step: Bend the LED 90 degrees from the battery cell using a half-twist, so that (1) it can bend that that way and (2) you don't touch the two leads of the LED to each other.

Place the LED assembly inside one of your jar lids and tape it down in place. (Optionally, you can do a better job of centering the LED than shown here!)

Finally, screw the jar onto the lid, and it's done.

With a little practice, you can make a few of these per minute.

And, after dark, they start to come alive.

We think that these could be potentially interesting for a number of different types of outdoor events-- making quick cheap lighting when and where it's needed. They are relatively scaleable, in the sense that hundreds of them are much more affordable than regular solar garden lights. The difference is that like traditional luminarias, these jar lights are temporary. However unlike luminarias, LED jar lights are waterproof, won't blow out or catch on fire, and will stay safely lit-- unattended-- for several days up to a week. And, if you don't need them for a week at a time, you can always easily disassemble them and save the batteries for next time.

• Eclipse Pies concept
• Explain that (party game idea?)
• Internet Pinball Database
• Miles to km... an interesting coincidence.
• A short sample of music played on the African Kora (Thanks Blaise!)
• Fantastic Fire Bowls
• Musée Patamécanique The Exhibition (Thanks Bobby!)
• Sunnyvale Walls
• Orbit Runner (Thanks Patti!)

A broken-in pair of jeans is one of the comfiest things in the world (denim is to humans as cardboard is to cats, right?). Unfortunately, they do eventually wear out. Luckily, they leave behind the best upholstery material: soft, comfy, durable denim. Chair seats wear out, too, especially kitchen table chairs, which can take a lot of abuse. Here we'll show you how to combine the two, reusing your old jeans and improving the chair. Reupholstering chair seats is straightforward. The seat bottom usually unscrews from the frame fairly easily.

The next disassembly step is removing the fabric covering. In most modern chairs, it is stapled on. You can usually pull most of the staples out just by gripping the fabric close to the staple and pulling upwards. Robo-grips are good for this, although other pliers will probably work, too.

I find that end nippers are effective for prying up particularly stubborn staples that I can't get with the robo-grips. Continue prying up the staples until the fabric comes off. Remove any remaining staples that might get in the way of the staples you'll want to put in later.

The foam padding is likely to be glued to the base. A little pulling and a little coercion with a razor blade can convince it to come off.

You'll need a new piece of foam. Pieces from the craft store tend to be priced rather high, but you can use an inexpensive mattress topper, which is likely to be cost-effective, especially if you have more than one chair or other projects you can use it for. Two layers of egg-carton style foam can mesh together to form a solid block. Place your seat platform on your foam pad and trace around it with a marker. It is preferable to be a little generous in the pad size. If it is too small, you could end up with a hard edge on your chair.

The last layer in your seat is the denim. Split the leg of a worn-out pair of jeans down the outside seam. You'll end up with a nice wide piece of fabric with the familiar flat felled seam in the center. Cut of a piece long enough to leave a few inches in all directions. Stack up your fabric, pad, and seat platform and get your staple gun ready.

Start by pulling the denim tight on one end and tack a couple of 1/4" staples in. Then pull the other end tight and tack there as well. Move on to the other two sides and pull tight and staple them down, too. Gradually work around the edges pulling tight for each staple. Be careful to avoid putting staples in where the screws attach the bottom to the chair. Fill in all the way around except for any corners.

Dealing with the corners is a lot like wrapping a present. You can fold in the sides and then fold over the front, or you can fold the corner over diagonally and tuck the excess material under. After the corner is down, cut away any excess fabric and add staples to fill in any remaining gaps.

Flip it over to admire it, and then screw it back onto the chair frame.

That wraps it up. You can now enjoy your comfier chair.

This technique will work for pretty much any shape, including round cafe-style chairs such as the one below.