Re: [ATM] Bronze reflectivity

[Anthony Stillman <atmer@flash.net>]

Thank you everybody for the interest.  There are so
many imaginative and insightful minds on this list. 
It doesn?t seem to matter what gets posted, there?s
always someone with information to add and/or a new
place to look for it.

Some of the ideas and suggestions for what to do I?ve
thought of BUT, all the time I miss details or worse
don?t recognize the ramifications until I?ve already
tossed dozens of hours down the bottomless pit of
ATMing.  Not that I?m complaining, except when things
catch fire, or I cut myself, or I drop something on my
foot, or something I?ve put a lot of time into breaks,
or?

Let me add a couple of things here.  First, the copper
oxide, boric acid, sand de-gassing flux I mentioned in
a previous post is difficult (read pain in the f?ing
a) to use.  It sucks up heat, it?s sticky as all get
out when hot and it makes a mess of a ceramic
crucible.   Second, when the melt is de-oxidized,
regardless of what is used to do it, zinc, aluminum,
red phosphorous, it?s appearance changes. The surface
tension drops so the meniscus at the edge all but
disappears. If the metal has been de-gassed first, the
change in appearance is startling.  It cast?s better
too.

Richard, I did not think of storing in argon, and I
didn?t know argon was heaver than air.  I do know that
there isn?t much in the air at the north and south
pole.  I didn?t mention annealing because it was 2 am
and I kind of lump it in with casting in my head.  I
shouldn?t.  My 40mm samples can go without annealing
and not split down the middle on their own.  Anything
larger has to go straight away into the kiln for at
least an hour.  Here?s another slide
<http://www.atmlist.net/contrib/atmer-at-flash-dot-net/anneal.jpg>

Thomas, CSIRO huh,  I?m on it.  I did find a Chinese
company that sells the de-oxidizing packets, by the
ton.  I?ve recently been buying small quantities
0.999x pure metals off ebay from emovendo (reliable
and prompt).  I found a dealer in the UK who is
selling red phosphorous, but I haven?t bought any yet.
 Plan to though, I figure it will be way easier than
harvesting it off match book covers.

Dave,  I?ll check woodworking stores and tool stores
for enviromental deoxidizers.  Now that I know where
to look.  I was just googling. I?ll get some camphor
at the drug store.  I have some problems with rust
developing on some of my jewelry tools too.  I oil
them but it doesn?t work that well.  I can cast and
polish 40mm diameter samples pretty quickly now.  I do
need to buy some more Tupperware.   A sacrificial
anode,  I think you mentioned this before and someone
else wrote that it wouldn?t work, so of course I?ll
try it.

Vladimir,  I?m not sure of the extent of atmospheric
pollution at the very beginning of the industrial
revolution.  I wonder the same things.  I only know
one active historian. Peter, care to chime in.  I
don?t know about tarnish versus oxidization either. 
Sulfides have clearly effected the sample of  Ag3Sn I
made two years ago.  It?s taken on the appearance of
slightly tarnished silver.  It took a few months for
it?s reflectivity (a qualitative evaluation) to drop
below the level of the speculum sample I made at the
same time.  Both are still aging away sitting quietly
on the shelf.

Dominic, yes I think of you first when I think how
nice it would be to have access to certified
calibrated equipment.  I know there are several other
professional scientists on the list (and a few off
list lurkers) but they don?t offer help nearly as
often as you.  Still I don?t like to impose.  I don?t
know about the effect of water vapor.  It never dawned
on me to store a sample in water, or oil, or any other
liquid.  An idea your post has inspired. Again, the
tremendous value of posting to the list.  I?ll try
powdered iron and powdered copper.  It kinda looks
like iron in the beef jerky de-oxidizing packets, but
I don?t know.

Three more slides I?ll share.  Looking down the tube
at an un-degassed un-deoxidized bronze metal mirror,
the telescope, and two pictures taken through it.

<http://www.atmlist.net/contrib/atmer-at-flash-dot-net/mirror.jpg>
<http://www.atmlist.net/contrib/atmer-at-flash-dot-net/telescope.jpg>
<http://www.atmlist.net/contrib/atmer-at-flash-dot-net/pictures.jpg>

Anthony


vis inertiae
Literally: The power of inertia.
It means: Couch potatoes tend to remain couch
potatoes.

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