When I really like a product I try to add something extra to my review – some justification my gadget-lusting readers might use to convince their partners they can't live without the latest Bluetooth speaker system or mobile upgrade.

This week, although I love the product, I'm afraid you're on your own. It's a robot that paints pictures on eggs – undeniably clever, yet completely unnecessary.

Egg-Bot is the brainchild of Californian artist and engineer Bruce Shapiro. The first Egg-Bot prototype dates back to 1990, but it was 2009 before Shapiro considered turning his hobby into a commercial enterprise.

I discovered Egg-Bot at the recent Mini Maker Faire – a one-day festival that brought together hundreds of artists, product designers and hardcore geeks at Summerhall in Edinburgh. Although they couldn't actually get Egg-Bot to work at the event (a neighbouring exhibitor with a massive, sparking Tesla coil ensured nothing in the vicinity functioned) I was fascinated enough to part with £185 for the deluxe model, complete with upgraded brass hardware.

The Egg-Bot arrives in kit form and takes around two hours to assemble. No instructions are provided in the box, but a web link takes owners to a comprehensive online instruction manual with easy-to-follow photographs.

Rather than using specialist inks or refills, Egg-Bot uses standard marker pens to do its drawing. There's a Sharpie included, but virtually any marker pens can be used in the machine. Multiple colours can be used in a design – the machine simply pauses after each colour to give you time to change pens.

Egg-Bot can draw on virtually anything round or nearly round and 3cm-10cm in diameter. So far I've tested the machine with eggs, oranges, table tennis balls, light bulbs and foam tennis balls.

Other owners have reported success with printing on golf balls, Christmas baubles, wine glasses and small vases, the latter printed with the machine standing on its end. Some adventurous types have even replaced the pen with a handheld engraving tool to etch images directly on to glass.

Drawing with the Egg-Bot is surprisingly easy. The included drawing software, Inkscape, comes with a ball-shaped template and lots of example designs. Text, illustrations and – with a bit of fiddling – photos can be included in an Inkscape design and from there it's just a couple of clicks to set the Egg-Bot in motion.

Watching Egg-Bot work is a lot of fun. Despite its Heath Robinson appearance and basic wood and fibreglass construction the machine is surprisingly fast and accurate.

It's just a pity nobody actually needs one.

Positives Fun to build and amazing to watch.

Negatives Difficult to justify for any practical purpose.


Twitter: @grant_gibson