Best Etched Meteorites?
Posted 08 September 2013 - 03:52 PM
Posted 08 September 2013 - 04:12 PM
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Posted 08 September 2013 - 05:47 PM
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Posted 08 September 2013 - 09:19 PM
Lintonius; nice Gibeons slices. I can't tell from looking whether ferric chloride or nitol was used. Ferric chloride leaves a higher contrast etch, but individual stones vary in etch appearance, so only a side by side comparison would help. Gibeons tend to have a very tight surface and lack any significant amount of chlorides to begin with, so the ferric chloride method is probably safer here than with the more corrosion prone varities like Campo, Dronino, Nantan, and Muonionalusta. Still, I would personally avoid it, I have a deep seated fear of chlorine contamination.
The way ferric chloride works is a bit indirect. Through a couple of reactions, HCl (hydrochloric acid) is produced, and that is what does the actual etching. It works more rapidly than nitol and produces a darker, deeper etch. Although I've never tried it, I suspect diluting the ferric chloride solution with distilled water would slow the etching process and give you a little more control.
For a discussion of etching techniques, you may consult appendix D of 'The Cambridge Encylopedia of Meteorites' (Norton) or 'The Meteorite and Tektite Collector's Handbook', (Bagnall; Wilmann-Bell).
Thank you, Lee. Former Michael Casper pieces.
Interesting info too, though I should do some more homework before making any decisions.
I should start by pulling out Norton's CEofM.
Posted 08 September 2013 - 09:34 PM
Lintonius- If you want to attempt to re-etch only one face, you can protect the other side with blue painters tape. Butt the seams tightly rather than overlapping, and press the tape firmly onto the surface making sure it's securely adhered at the edges. Sand the surface with 600 grit wet/dry automotive type sandpaper, keeping all the lines straight in one orientation only. The paper fills up quickly, so keep fresh abrasive on the surface. You're trying for a uniform hazy polish. The concentration of your etchant should be such that it takes a couple of minutes for the process to complete, any quicker and it's difficult to control resulting in too dark an etch.
Yeah Lee. I might try the back first, so I don't lose the etch I already have. I used a random-orbital sander on prior etchings (long-time woodworker;^). I take it you don't recommend that?
Posted 09 September 2013 - 12:15 PM
I got my first large Campos from Michael Casper, a great person to do business with, and a fascinating individual in person.
Posted 14 September 2013 - 12:58 AM
Does your method of etching give the etch more of a matte look rather than a shiny look. Or is that the difference in types of irons. I really like the look of your Campo del Cielos which don't reflect so much light. Both the Gibeon and Taza etchings I have are quite reflective as if there is a protective coat of something on there. I don't like these as much.
Posted 14 September 2013 - 03:15 PM
Not to say you can't get good results etching a mirrored surface. Since the acid dissolves only the kamacite and leaves the taenite unaffected, that portion ought to remain quite reflective. Some species require a fully polished surface to show a good etch, such as Canyon Diablo and Mundrabilla. Etching these after only a 600 grit finish leaves a muted pattern with poor contrast in my experience.
Some folks do coat their pieces with lacquer or polyurethane. Those should appear uniformly shiney regardless of the viewing angle. Close inspection should reveal if you've got a coated piece. If there is a sprayed on coating, you will be able to slightly dent it with a gently applied fingernail without causing any damage.
Posted 14 September 2013 - 03:18 PM
Posted 15 September 2013 - 10:37 AM
I wonder if Def is a brand or type of clear coat.
Posted 15 September 2013 - 03:51 PM
I just received a 2nd e-mail from the Gibeon seller. "Yes that one had a protective coating put on it called vpci 286 meteorite top coat."
Posted 15 September 2013 - 04:19 PM
Posted 15 September 2013 - 10:22 PM
I'm a bit familiar with Paleo Bond through their literature, but have no direct experience with the products. I believe they're highly thought of though.
I came to use gun oil as a protectant after reading an article by Allen Langheinrich (Lang's Fossils and Meteorites) on the care and preparation of irons. It appears in the August 1997 issue of Meteorite!, which I'm pretty sure is out of print.
The use of a clear coating is nice because it enables frequent handling of a specimen. I'm not sure how they hold up over time, I'd certainly be glad to hear from anyone who's had a similarly prepared slice for a number of years. I did at one time coat my pieces, but found even the tiniest bit of trapped moisture became problematic over time, compromising the coating and accelerating corrosion at that point. I like gun oil because it penetrates into any microscopic fissures, and is easily reapplied if necessary. I have quite a few pieces treated with G-96 oil, slices and whole specimens that have remained corrosion free for years, and that is in a fairly humid environment.