OT- Glow in The Dark Sandblasting Sand?

I've been using my sandblasting cabinet

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for a while now & have always used glass grit as an abrasive. One of the neighbours had some cast wood stove parts he wanted to clean up & he shows up with a couple of bags of sand to do it with. We loaded her up & let rip whereupon I noticed that where the sand was impacting the metal there was something that looked like a a pale blue spot of light. It only showed when the nozzle was within an inch or so of the metal. It was bright enough that I could see exactly where the sand was hitting even through the dust & a rather hazy window.

Was I imagining it or is there actual light being generated?

If there is light is it electrostatic discharge or are the sand grains exibiting some sort of piezoelectric effect from the shock??

Enquiring Minds Want To Know-

H.

Reply to
Howard Eisenhauer
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It does sound suspiciously piezo to me... What "flavor" sand was being used? If it's a quartz based sand, rather than the more usual "silica sand", that might go a long way toward explaining it, since quartz does do the piezoelectric thing.

Can't rule out static buildup, either, but good Sir William's shaving device leads me to lean toward piezo effects as the source.

Reply to
Don Bruder

Aloxite grit does it too, its an electrostatic effect, caused by the particles being charged by friction as they rush up the pipes to the nozzle tip. Charge is transferred and stored on the object until the potential is high enough to discharge away, or it leaks through something. Certainly you get a stronger effect if you hold the object away from the walls with the cabinet gloves.

Steve

Reply to
Steve

Uh, silica IS quartz.

Reply to
Richard J Kinch

It's called triboluminescence. I'm not sure if it is known what causes it, but I expect Google will have some ideas. You can demonstrate it with sugar in a coffee grinder.

Reply to
Newshound

Actually, by my understanding, quartz is indeed a form of silica, but the reverse isn't necessarily true. For piezo to be involved, the crystal structure is important, and not all forms of silica have the right structure. Silica in the form of quartz has the right structure. Silica in most of its other forms doesn't.

Reply to
Don Bruder

Common 'silica' is an amorphous supercooled fluid. Some pundits even argue that it continues to flow (albeit slowly) in its 'solid' state. I dunno.

Quartz is crystalline.

LLoyd

Reply to
Lloyd E. Sponenburgh

In the case of common sand, it is. The yellow stuff on the beach is quartz with some iron (oxide). Silica sand is also called quartz sand.

The hardest mineral in any abundance is sorted out by the surf to be beach sand, all softer minerals (such as calcium carbonate, which is much more abundant) being milled to dust in a sort of competition.

If diamonds existed in any abundance, we'd have diamond beaches instead of quartz.

Reply to
Richard J Kinch

Not so. See, for example,

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. Partial " The most common constituent of sand in inland continental settings and non-tropical coastal settings is silica, usually in the form of quartz because the considerable hardness of this mineral resists erosion. However, the composition of sand varies according to local rock sources and conditions. "

Ted

Reply to
Ted Edwards

Reply to
David Billington

I sometimes use an abrasive grit blaster at work. It does the same thing on carborundum grit, but at least in my case it's static electricity causing the glow. The charge can and does build up to the point where the rubber gloves on the cabinet break down and you get a nasty static shock. I have seen it jump at least 3/8" of an inch to anything grounded. This usually only happens in fairly dry weather on this machine. Our plant air is also very dry as it all goes through a aftercooler and chiller drier before being piped around the building. The dry air probably increases the buildup of charge. If somebody took the time to run a ground wire to the gun body on our machine this probably wouldn't have to happen...

Reply to
oldjag

Another one that's weird: I run a night-time-delivery newspaper route. Rolling the papers and rubber-banding them produces the most interesting flashes and tracers when you pull off and shut down the car to do it. I thought for sure I must have been having an acid flashback or something the first time I saw it, but then one night I mentioned it to the other carriers while we were sitting around over coffee waitnig for the papers to get to the loading dock. Found out I *WASN'T* crazy after all - Only the newest two of the 16 present hadn't noticed the phenomenon.

Oddly enough, it only happens once per rubber band - The first time you stretch it, it'll give off a surprisingly strong phosporescent blue-ish glow that persists for several seconds before fading if you hold the stretch. After the first stretch-and-release cycle, it doesn't do anything at all. (or if it does, it's so faint that I haven't been able to detect it) Dunno if it's something about the particular brand of rubber bands the paper gets for us, or what, but the first couple times it happened at "oh-dark-hundred" out in the middle of nowhere where it's

*TRULY* dark at night, I thought for sure I must have been losing my mind!

I've also heard that you can (or could... dunno if you still can) get the same sort of thing by stretching a stick of "Fruit-Stripe" chewing gum, but haven't ever tried it. Wrigley's and such supposedly won't do it. I wonder if it's related?

Reply to
Don Bruder

Seems to confirm exactly what I said.

Reply to
Richard J Kinch

According to Don Bruder :

And the same effect if you peel the tape holding film to the spool in 35mm film just before processing it. Some people just tear the tape where it passes around the spool, but I didn't like the tape being in the processing chemicals, so I would peel it, and wound up with the most interesting patterns on the last half inch or so of the film. This was Tri-X, push processed to 800 or 1200 ASA, FWIW.

Interesting. I had not heard of *that* one.

Enjoy, DoN.

Reply to
DoN. Nichols

Ok - here from my University book - minor in Geo :-)

Tektosilicates Silica Group Quartz - SiO2 Tridymite-SiO2 Cristobalite-SiO2 Opal-SiO2 Feldspar Group (contains Na,Ca, & K (AlSi3O8) (different colors/shapes/..... Orthoclase - K(AlSi3O8) { big rich group of crystals } Mica Group ..... One of the reasons for the unique properties of Tektosilicates - it can be put into solution and trees draw it up - as well as growing large crystals of all sorts. Opal is one of those.

Quartz likely refers to 'pure' crushed crystal.

Silica sand - likely refers to sand made from one or more elements of the Silica group or Tektosilicates.

Martin

Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH & Endowment Member NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member

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Reply to
Martin H. Eastburn

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