Transcript Meteorite - Arkansas/Oklahoma Astronomical Society

Meteorite 101
Cutting, Surface Preparation, Etching,
and Preserving Iron Meteorites
Prepared for AOAS By Leonard Lynch
Introduction
The purpose of this presentation is to teach you
the basic steps in Cutting, Surfacing, Etching,
and Preservation (Rust Prevention) of
Nickel/Iron Meteorites.
Types of Cuts
Slices & Slabs
Slice Shapes
End Cuts and Windows
Continued:
3D Shapes
Jewelry and Coins
Knives & Other Objects
Step #1: Cut The Meteorite
Iron Meteorites are usually cut with a horizontal
band saw.
Though very efficient at cutting metal, the
blades leave saw cut marks that must be
removed.
Continued:
Note: “Window Cuts” can be made with the use of a Belt
Sander alone. Using a belt sander, work an area on one
end, until it is Smooth and Flat, then continue to step
#3.
After you determine where you want to cut (Slices, End
Cut or Window), secure the meteorite in the saw vise.
A loose vise or slack saw blade can result in very deep
saw marks and uneven cutting that can be hard to grind
out.
Carefully cut the meteorite.
Step #2: Surface Preparation - Removing the Saw Marks
As you can see from the photo above, cutting a meteorite
leaves obvious saw marks that must be removed.
The best way to do this and not add to the surface marks
or alter the surface flatness, is to use a “Table Top Belt
Sander”
Continued:
Table Top Belt Sander with 6” Vertical Disc Sander
Do not use the Vertical Disc Sander because it is too
easy to gouge and leave deep scratches from the edge
of the disc, that results in more sanding than would
have been necessary.
Continued:
Use the vertical belt sander to remove the saw marks.
I use a 80 to 120 grit belt. Keep the meteorite
orientated always in the same direction on the sanding
belt. This will keep all sanding marks going the same
direction and easier to remove.
Step #3: Hand Sanding
When all of the initial saw marks are removed, use a
orbital/vibration hand sander with progressively
smaller grit sand paper. This will give the meteorite
surface a mirror finish.
Continued:
With the hand sander try to keep the surface of the meteorite
level with the surface of the sand paper. Avoid sanding the edge
of the meteorite. You do not want to “round the edges”
(Note: be very patient. This step will take a while...About 1 to 2 hours
per grit of sand paper.)
I start off with 200 grit sand paper. Sand the meteorite surface
until all of the visible belt sanding scratches are gone. These
scratches are easy to see and go in one direction, if step #1 was
followed. The hand sander leaves smaller scratch marks.
(Note: Buy sand paper that is made for use on metals, not wood. It will
last longer)
Continued:
Next use 500 grit sand paper. Use this until all the scratches from the 200 grit
paper are gone. You will begin to see a mirror finish develop on the meteorite
surface.....
Next, use 1200 grit sand paper. As before, use this paper until all previous
sanding scratches are removed. At this point the surface of the meteorite
should have a mirror like finish with small vibration scratches. These are
caused by the vibration of the hand sander and can be easily removed by using
a piece of 1200 grit sand paper by hand, on a sanding block, for about 10
minutes or so.
Step #3: Etching the Meteorite
For this step, you will need the following items and materials:
* 2 Flat, Shallow Plastic Bowls
* Rubber Gloves
* 12 ounces of water
* 2 ounces of Ferric Chloride (Etching Material) This is my
preference. A solution of Nitric Acid may be used instead.
* Paper Towels
Continued:
CAUTION – Ferric Chloride (or Nitric Acid) can burn sensitive
skin. Always were rubber gloves during use.
These chemicals will also etch ALL metal surfaces. Ferric
Chloride will stain concrete and other porous materials such as
skin, clothing, wood, floor tiles or counter tops. Be very careful
not to spill or drip the chemicals.
* Cover work area with Paper Towels.
* Place the Plastic Bowls on the paper Towels.
* Put on rubber gloves.
* Carefully pour 1 to 2 ounces of the etch material into one bowl
and a few ounces of water into the other bowl.
Continued:
NOTE: If the meteorite has had oil or another rust preventative
(such as WD-40) applied to the sanded surface, wash the
meteorite with dish washing soap and water to remove it.
* Carefully place the meteorite, sanded surface side down, into
the etching material, letting it set in the solution.
* After about 60 to 90 seconds, remove the meteorite from the
etch solution and place in the bowl containing water. This will
stop the etching process.
* Remove the meteorite from the water and inspect the surface.
A good etch will bring out the “"Widmanstätten" pattern. This is
basically the crystalline structure of the metal as a result of
cooling over thousands to millions of years. If a deeper etch is
preferred, you can go back through the etching process.
Continued:
Fine
Coarse
Widmanstätten Patterns
Buffing with Jeweler's Rouge will put a shine back on the
surface, but if buffed too much, you will need to re-etch.
Continued:
When all etching is completed, again wash the meteorite
throughly in Dish Washing liquid and water.
Step #4: Preserving Iron Meteorites
Two major factors that cause a Iron/Nickel Meteorite to rust are
Chlorides, both natural occurring and what is added during the
etching process and Water (Moisture). The more of either, the
more the meteorite will rust.
If you used Ferric Chloride as an etching material, you have
added a considerable amount of chlorides to the surface and into
surface cracks that will result in rust if not removed.
We must also remove the water we washed the meteorite in
during the etching process.
Continued:
Removing Chlorides
Mix a solution of Sodium Hydroxide and Ethanol. Use about one
Table Spoon of Sodium Hydroxide to a pint of 96% Ethanol.
Submerge the Meteorite in the solution and let it soak for 5 - 10
days in the alcohol / sodium hydroxide bath. The sodium
hydroxide will attack the Chlorides in the specimen through a
chemical reaction that combines sodium in the solution with the
chlorides on the meteorite surface and in minute cracks and
becomes common salt (Sodium Chloride). Wash the meteorite
throughly with Dish Washing Liquid / Water.
Removing Water
Next, soak the Meteorite in pure 96% Ethanol for 24 hours.
Place the meteorite in you kitchen oven at the ovens lowest
temperature setting for two hours.
This completes the drying process.
Final Treatment
The final treatment to the meteorite is to apply a coating of oil
to all surfaces of the specimen. I use WD-40, but any light oil
will work
I do not recommend using a coating such as varnish,
polyurethane, etc, because over time most coatings will turn
yellow and if you ever need to re-etch the meteorite, you would
need to first remove the coating.