What caused these strange dust patterns?

While cleaning out the garage this afternoon, I pulled my leaf blower out of its box to clean it off (it was put away quite dusty), only to notice some very strange shapes in the dust. A picture:


What in the world caused these patterns? The blower was dry and shielded from the elements for the past three months, as far as I can tell. My only guess is that this was caused by some kind of bacterial or fungal growth, but I’ve never seen anything like it before.

My guess: a little frost formed on the blower, attracted dust, then the frost disappeared leaving the dust behind.

I’d bet money on those being caused by static electrcity discharges. They have the same brancing dendritic shape that is characteristic of electrical discharges over an insulating material.

I saw something like that on a lawnmower… The owner of it said it was from static electricity, as Q.E.D. said. But I don’t know how the owner knew this fact.

could be bacteria

Some salts, particulary the more hygroscopic ones such as CaCl[sub]2[/sub], will do the same sort of thing if left on a surface long enough. Repeated cycles of dissolution and solidification drive the process.

They look kinda like crop circles to me.

Mangeorge might be onto something. Teensy UFO’s are often attracted to power tools. Seriously, I’ve seen formations like this result from drops of gasoline spread out by wind or air pressure.

I don’t think that’s it, AskNott. The OP said the blower was kept “dry and shielded from the elements”. This kinda kills Squink’s theory as well, IMO.

I’ve seen this many times on mold injected plastic parts. Where the parts are complex, it seems that the static electric pattern you are seeing is somehow related to the way the plastic flows when it is injected into the mold. I’ve never taken a photo then wiped the dust away to see if it came back a second time in exactly the same pattern.

Not necessarily. Hygroscopic salts pull humidity out of the atmosphere, thus supplying their own moisture. It’s doubtful that JRR’s “dry and shielded from the elements” implies that the blower was in a hermetically sealed box along with a packet of phosphorous pentoxide or similar desiccant. The material on the blower appears to be a white salt, rather than brown or greyish dust, and the prominent dendrites all grow out of diffuse patches of denser material. You can also see some dendrites on the label, which is likely to have static properties which are different from plastic of the blower tube. There’s also the question of where the static charge would come from in a stored blower. Unlike water absorption by hygroscopic salts, high static potentials don’t just suddenly appear on stored objects. I don’t discount the possibility that static might have had something to do with the patterns, but IMO solution chemistry is the more likely culprit here.


Looks like mold to me. A very similar pattern appears on improperly stored camera lenses.

The “static” theory sounds interesting, but are people suggesting that a discharge occured spontaneously? Or just a static buildup? Maybe it’d help if JRR could tell us what material the surface is.

I’d be more interested in his assesment of the material of the patterns itself. I notice in the photo he seems to have wiped a section clean possibly by handling, and you can clearly see a portion of some of the patterns smeared off. The material the patterns is composed of seems to behave more like dust than either crystal growths or bacteria, both of which I would expect to adhere more strongly. I have some high-voltage stuff laying about and being less than a great houskeeper, I have plenty of dust around. I’ll see if I can replicate these patterns, in the interest of science.

After some experimenting, I was able to create some branching dust patterns on a piece of ABS plastic. They bear a superficial resemblance to the dust patters in the photo linked to in the OP. A photo of mine can be seen here. I used a source of -15kVDC to create latent electrostatic patterns on the inside of the cover for my Casio graphing calculator, which had been cleaned of any oil and dirt and allowed to air dry. This isn’t meant to suggest the patterns asked about in the OP were formed in this manner, only that such patterns can be formed by static electricity. The OP doesn’t mention exactly how the blower was stored, only that it was in a box. Was it also wrapped in plastic, or supported in styrofoam packaging of some sort? If so, I’d suggest that the patterns were created at the time it was unpacked as a result of removing the wrapping or packaging, rather than there having been latent patterns on the surface at the time the unit was put in storage. I’ll continue to try to create patterns more similar to the ones see in the OP’s photo. I love science! :smiley:

Static electricity cam be generated by the action of air (and objects) moving up through the intake of the vacuum cleaner; this is why it’s not a very good idea to use a regular vacuum cleaner to remove dust from inside your PC.

This is caused by static. I’ve observed the same phenomenon on my vacuum cleaner.

Q.E.D. - I’d love to see the picture, but - your link didn’t work for me; I got a page unavailable error.

Stupid Geocities. Ok, try this new link.

Cool. Have you got a polarizing filter ? You might see the same pattern as stress marks in the plastic. Of course you haven’t got the dendrites radiating from a central point.