I've been using my sandblasting cabinet
(http://users.eastlink.ca/~howarde/Sand%20Blaster.html) 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.

In article ,
Howard Eisenhauer wrote:

I've been using my sandblasting cabinet
(http://users.eastlink.ca/~howarde/Sand%20Blaster.html) 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.



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.

--
Don Bruder - - If your "From:" address isn't on my whitelist,
or the subject of the message doesn't contain the exact text "PopperAndShadow"
somewhere, any message sent to this address will go in the garbage without my
ever knowing it arrived. Sorry... http://www.sonic.net/~dakidd for more info

Don Bruder wrote:

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.


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

Don Bruder writes:

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.

Uh, silica IS quartz.

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.

In article , Newshound says...

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.

Heh, the all-time best way to demonstrate this is with Wintergreen
Life-Savers.

I'm not sure why the wintergreen ones are so impressive, but they
work the best.

Materials required for demonstration: pack of life-savers, darkened
room with mirror.

Chew lifesavers with mouth open, in front of mirror with the room dark.

You'll see all kinds of great sparks inside your mouth.

Bonus points if you do the experiment with a friend of the opposite
sex.

Jim


--
==================================================
please reply to:
JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com
==================================================

In article ,
Richard J Kinch wrote:

Don Bruder writes:

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.

Uh, silica IS quartz.

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.

--
Don Bruder - - If your "From:" address isn't on my whitelist,
or the subject of the message doesn't contain the exact text "PopperAndShadow"
somewhere, any message sent to this address will go in the garbage without my
ever knowing it arrived. Sorry... http://www.sonic.net/~dakidd for more info

"Don Bruder" wrote in message
...
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.

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

jim rozen wrote:

Chew lifesavers with mouth open, in front of mirror with the room dark.

You'll see all kinds of great sparks inside your mouth.

Bonus points if you do the experiment with a friend of the opposite
sex.

((chuckle))

Yeah, chewing with your mouth open
is a great social activity ;-)

BugBear

Bonus points if you do the experiment with a friend of the opposite
sex.


No really, Jane, you can't see it unless we pull the covers over us.

sigh...
university was a LONG time ago... ;-)

Don Bruder writes:

Actually, by my understanding, quartz is indeed a form of silica, but
the reverse isn't necessarily true.

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.

Richard J Kinch wrote:
Don Bruder writes:
Actually, by my understanding, quartz is indeed a form of silica, but
the reverse isn't necessarily true.

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.

Not so. See, for example, http://en.wikipedia.org/wiki/Silica .
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

On a similar line if you open pre-gummed envelopes in a darkened room
the adhesive produces a glow as you open it.

Howard Eisenhauer wrote:

I've been using my sandblasting cabinet
(http://users.eastlink.ca/~howarde/Sand%20Blaster.html) 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.

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...

Ted Edwards writes:

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.

Not so.

The most common constituent of sand in inland continental settings and
non-tropical coastal settings is silica, usually in the form of quartz
...

Seems to confirm exactly what I said.

According to Don Bruder :
In article ,
David Billington wrote:

On a similar line if you open pre-gummed envelopes in a darkened room
the adhesive produces a glow as you open it.

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.

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.

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

Enjoy,
DoN.
--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

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


Don Bruder wrote:
In article ,
Richard J Kinch wrote:


Don Bruder writes:


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.

Uh, silica IS quartz.


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.


----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==----
http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups
----= East and West-Coast Server Farms - Total Privacy via Encryption =----