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  1. Science & Tech
20 May 2014updated 05 Oct 2023 8:26am

The Blob is real, sort of (it’s magnetised silly putty)

Both a neat toy and a delightful illustration of how magnetism works.

By Ian Steadman

Occassionally there’s cause to take a break from seriousness here at NS towers, and that usually happens when we see a cool gif on the front page of reddit – like this one:

You’re looking at magnetic putty, desperately trying to connect with another magnet held just out of reach. Like the Blob, it wishes to consume all it can (as long as it can eat other magnets).

As the name suggests, magnetic putty is what results from adding tiny magnets – on the scale of a micrometre in size, or a thousandth of a millimetre – to silly putty. It usually comes in small tins, because while it’s fun to play with the magnetic aspect makes it tricky stuff to clean up if it gets its way with other magnetised objects. For example, this small cube, which it devours gladly:

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What is actually happening inside magnetic putty, though? It’s more complex than a normal magnet (and god knows they’re complicated enough), with north and south poles and clearly delineated fields of force between them – as seen in that primary school science lesson with iron filings scattered on a piece of paper, to give cool images like this. Inside magnetic putty each magnet is tiny, with a field that is simultaneously being warped by the presence of the other magnets around it.

This means that, when it’s sitting on a desk not near anything else, the putty looks just like normal putty. Yet stick anything magnetised nearby and the tiny magnets will each rotate so that their north pole tries to reach the nearby south pole (or vice versa). They can’t move through the putty, so they drag it with them. In the gifs where the putty is consuming magnets whole, it’s creating a slow-motion replica of what happens when you shake filings over a piece of paper over a magnet – the putty’s magnetised filings are recreating a gooey version of that diagram of magnetic force.

You can actually make your own quite easily, thanks to a how-to posted on Instructables – all it requires is a neodymium magnet, iron filings and normal silly putty. That said, be very careful with neodymium magnets. They’re extremely strong, can start moving towards each other faster than you can realise, and can move fast enough to sever fingers or make holes in flesh just as a bullet would. Here’s a safety demonstration video of a man having his hand destroyed by a neodymium magnet that should scare you off (tw: graphic violence).

However, on a happier note, thanks to this video from Vat19 (who sell the stuff), we can make some great gifs of our own of a massive lump of magnetic putty – something like 45kg – absorbing big magnets:

Press play on this – it’ll help:


So satisfying.

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