-----Original Message-----
From: Judy Wood [woodj@clemson.edu]
Sent: Wednesday, March 01, 2006 8:01 AM
To: Jones, Steven
Cc: xxxx@clemson.edu; mzebuhr@clemson.edu; xxxx@clemson.edu
Subject: Glowing aluminum pictures

PURPOSE:
The purpose of this exercise was to demonstrate that aluminum does indeed glow.   This work was conducted at Clemson University with Michael Zebuhr on 28 Feb 2006.
 

METHOD:
The aluminum (99.7%) is heated in a tungsten boat by electrical current through the tungsten "boat" clamped at each end.   The square and rectangular pieces on the end are copper, with several rounds of aluminum evaporations on them.

The aluminum wire segments are stacked in the tungsten boat.  It's not the clearest picture, but you can tell that the aluminum is a dull color (oxidized?)
 
 

Here, the Aluminum wire is beginning to bend over the edge.  It may not be obvious, but the boat is just beginning to glow.  The aluminum looks a little more shiny.

Notice that the aluminum has melted, or is about to melt, and still appears silver.  It looks like it dripped over the edge, but that's just where the wire drooped over the edge.  The thick piece of wire that is hanging straight down looks more shiny than it did before it was heated.  This is true for all of the aluminum.

After melting, the aluminum forms a ball.  (It looks like a rising loaf of bread!)   Notice that the drip hanging below (near the right end of the boat) is glowing, yet has a more silver color than the "bread loaf."

Notice the drip on the under side, hanging down.  The surface tension seems to be fairly high.   Notice that the drip hanging below (near the right end of the boat) is glowing, yet has a more silver color than the "bread loaf," indicating that it is slightly cooler than the aluminum on the other side.  Also, the tungsten boat this drop is hanging from is a dark red. 

Let's consider the evidence.  Turn on a standard 60-Watt incandescent light bulb and see if it has "low emissivity."  The filament is almost certainly made of tungsten.  In the pictures Michael took of the glowing aluminum, the aluminum is sitting on a tungsten "boat."  The aluminum has the same glow as the tungsten.  So, we can conclude that the aluminum and the tungsten have the same emissivity. 
 
 

This is the same image I have in a video clip.  The dark spot at the top looks silver and dances around like it's boiling.

You may notice the darkened appearance around the copper block that clamps the end.  That's what I refer to as the high-pressure "evaporation."  What you see is from these experiments alone.  Notice that the drip hanging below (near the right end of the boat) is glowing, yet has a more silver color than the "bread loaf."

Here is where we abruptly turned down the current, cooling the tungsten boat.  The aluminum is still glowing.  Note that the drip on the under side, near right end, looks silver.  I believe it looks silver at a slightly lower temperature than the red glow, although it is (just barely) melted.

In full atmospheric pressure, I think the surface may be more likely to look silver (a) because of the temperature loss adjacent to the surface, and (b) there may be some reaction with the air, just on the surface.  But that would only be an issue at the "just-barely-glowing temperatures.

The "rising loaf of bread" appearance is interesting.  This is caused by the low-pressure environment, but may exist in atmospheric pressure, too, as the result of high surface tension.

Other examples of glowing molten aluminum.
 
 

Molten Aluminum
Figure #9a:  Temperature chart	Figure #9b:  Molten aluminum at approximately 930°C - 1100°C.  Source:  The International Aluminium Institute
Figure #9c:  The team casts a crankcase from aluminum. PHOTO BY JUDY HAY source: Popular Mechanics

from the book:  Build an Oil Fired Tilting Furnace by: Steve Chastain

Figure #10a,b  These images are from a book showing how to melt aluminum and separate it from the slag. It has been discussed that these two pictures may not be aluminum, but no one is absolutely sure. On Jim Fetzer's radio show, Steven Jones identified this material as looking "silvery," implying that he, too, thought it was aluminum. However, the point is that no one is really sure. Can you tell by looking at it what metal it is, especially if you don't know the temperature of it? What has slopped over onto the sides and cooled does indeed look "silvery."     The molten aluminum is glowing.  The environment is at atmospheric pressure.  The lighting is "daylight conditions" (outside). Source:  http://www.metalwebnews.com/howto/furnace2/melting.html

See also the glowing aluminum page in memory of Michael Zebuhr.