Hi folks,

I'm looking for some etched specimens of common metals so that I can
photograph them under a microscope. Most importantly cast iron and hot
rolled mild steel. I'll pay a fair price for samples in good condition,
or maybe swap them for something you're looking for. Anyone know where I
might obtain some?

Best wishes,

Chris

Christopher Tidy wrote:
Hi folks,

I'm looking for some etched specimens of common metals so that I can
photograph them under a microscope. Most importantly cast iron and hot
rolled mild steel. I'll pay a fair price for samples in good
condition, or maybe swap them for something you're looking for. Anyone
know where I might obtain some?

Best wishes,

Chris

Chris,

Have you tried asking at a local university that does Mech Eng or
similar. We did polishing and etching of materials to examine the
structure on my Mech Eng course, I would have thought others would be
similar unless the powers that be have deemed it too dangerous playing
with dilute acids these days.

David Billington wrote:
Christopher Tidy wrote:

Hi folks,

I'm looking for some etched specimens of common metals so that I can
photograph them under a microscope. Most importantly cast iron and hot
rolled mild steel. I'll pay a fair price for samples in good
condition, or maybe swap them for something you're looking for. Anyone
know where I might obtain some?

Best wishes,

Chris

Chris,

Have you tried asking at a local university that does Mech Eng or
similar. We did polishing and etching of materials to examine the
structure on my Mech Eng course, I would have thought others would be
similar unless the powers that be have deemed it too dangerous playing
with dilute acids these days.

Thanks for the suggestion. I've asked a friend of mine who's doing a PhD
in materials science, but he said he's mostly on the theoretical side
and rarely sees samples. A local university is a possibility I guess,
but we're a bit short on them here in Shropshire. I wouldn't mind
etching my own, but it's a bit hard to get hold of the concentrated
nitric acid need to make the etching solution. I might try posting this
on uk.rec.models.engineering and see if anyone has further ideas.

Best wishes,

Chris

"Christopher Tidy" wrote in message
...
I wouldn't mind etching my own, but it's a bit hard to get hold of the
concentrated nitric acid need to make the etching solution. I might try
posting this on uk.rec.models.engineering and see if anyone has further
ideas.

Best wishes,

Chris


Hi Chris.
Wish I could help, but Sydney is a bit remote from you.

You don't need conc. nitric to prepare ferrous specimens. Nital is a quite
gentle etchant. I forget the exact concentration (its been a while) but its
around 2-4% IIRC. Vinegar-like strength. (more below)

By far the most challenging aspect is the removal of scratches caused by
contamination from the next-largest-sized abrasive. Especially when you get
to the diamond lapping phase. If you slip up and transfer a few micron's
worth of "coarse" diamond abrasive onto the fine abrasive lap, then you have
to chuck out the lap ($$$!) and start again with a freshly charged one (more
$$$). Otherwise your samples show scratch patterns that look like a piece
of fibreglass mat.

Mounting samples - easy
Coarse grinding - easy } all of
Fine grinding - easy } these stages
Coarse wet&dry - easy } done under
medium wet&dry - easy } running
fine wet&dry - easy } water
coarse lapping - pretty easy
fine lapping - an absolute unutterable frustrating *******
etching - easy, quick and safe.

Cleanliness to a hospital standard is not enough. You must be much more
finicky than that. Hands must be washed thoroughly (and I mean *thoroughly*)
between grades, and clothing must not be allowed to come into contact with
any of the abrasives or the rinse water. I used to scrub myself red-raw on a
day of specimen preparation.

Nowadays, if I were to do it again, I would use disposable latex gloves.
(No-brainer)
I'd probably use about 20-30 per sample.

But etching? Piece of cake. Dunno how difficult it is to source nitric
post 9/11, but any school should have the tiny amount of low conc. you need
to prepare Nital. Nital recipes call for conc. nitric + ethanol, but you
can easily substitute lower concentrations. The worst effect will be longer
etching times. No big deal.

(Strangely, its kind'a sad to etch a specimen. You spend ages getting a
beautiful lustrous mirror-perfect (literally) surface, only to lose it all
for the dull grey surface of an etched specimen. Siggghhh)

Have fun.

No - really. It *is* fun.

--
Jeff R.

"Jeff R." wrote in message
u...

....follow-up...

Look at http://www.metprep.co.uk/history6.html

Very useful.

--
JR

On 2008-01-24, Jeff R. wrote:

[ ... ]

You don't need conc. nitric to prepare ferrous specimens. Nital is a quite
gentle etchant. I forget the exact concentration (its been a while) but its
around 2-4% IIRC. Vinegar-like strength. (more below)

By far the most challenging aspect is the removal of scratches caused by
contamination from the next-largest-sized abrasive. Especially when you get
to the diamond lapping phase. If you slip up and transfer a few micron's
worth of "coarse" diamond abrasive onto the fine abrasive lap, then you have
to chuck out the lap ($$$!) and start again with a freshly charged one (more
$$$). Otherwise your samples show scratch patterns that look like a piece
of fibreglass mat.

[ ... ]

(Strangely, its kind'a sad to etch a specimen. You spend ages getting a
beautiful lustrous mirror-perfect (literally) surface, only to lose it all
for the dull grey surface of an etched specimen. Siggghhh)

Out of curiosity -- don't you need something like a
phase-contrast microscope to see the results? I had one at work for
viewing integrated circuit dice, but I believe that it was normally made
and sold for metalurgical purposes. And a normal microscope won't show
nearly as much data.

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 ---

"DoN. Nichols" wrote in message
...

Out of curiosity -- don't you need something like a
phase-contrast microscope to see the results? I had one at work for
viewing integrated circuit dice, but I believe that it was normally made
and sold for metalurgical purposes. And a normal microscope won't show
nearly as much data.

Enjoy,
DoN.

Nup.
A plain old reflecting microscope will keep you entertained for hours. It
all hinges on good polishing and etching, of course. These 'scopes always
have (and need!) built-in lighting, which operates axially.

I don't even know what a phase-contrast microscope *is* ! :-(

If it does what it sound like it does, then it would be great - yes - but
not necessary.

I've gone up to pretty impressive magnification(s) with the oil-immersion
lens, too.

Sigghhhh... Memories.

--
Jeff R.

Jeff R. wrote:
"Christopher Tidy" wrote in message
...

I wouldn't mind etching my own, but it's a bit hard to get hold of the
concentrated nitric acid need to make the etching solution. I might try
posting this on uk.rec.models.engineering and see if anyone has further
ideas.

Best wishes,

Chris



Hi Chris.
Wish I could help, but Sydney is a bit remote from you.

You don't need conc. nitric to prepare ferrous specimens. Nital is a quite
gentle etchant. I forget the exact concentration (its been a while) but its
around 2-4% IIRC. Vinegar-like strength. (more below)

I ought to be able to lay my hands on dilute nitric acid, but it's
diluted in water. My understanding is that the etch needs to be made
from nitric acid in ethanol or methylated spirit. There's also
apparently some reason why you shouldn't store the etch either.

What the effect of trying to etch specimens in dilute nitric acid would
be, I don't know. Would they go rusty? If it works, that would be neat,
because dilute nitric acid is far easier to source.

See my latest thread on microscopes.

Best wishes,

Chris

Jeff R. wrote:
"Jeff R." wrote in message
u...

...follow-up...

Look at http://www.metprep.co.uk/history6.html

Very useful.

Thanks for that link!

Best wishes,

Chris

Christopher Tidy wrote:

I'm looking for some etched specimens of common metals so that I can
photograph them under a microscope.

Now I really want to know what you are planing to do with them together with
the microscope ...


Nick
--
The lowcost-DRO:
http://www.yadro.de

Nick Mueller wrote:
Christopher Tidy wrote:


I'm looking for some etched specimens of common metals so that I can
photograph them under a microscope.


Now I really want to know what you are planing to do with them together with
the microscope ...

Take photographs. If you want to know what I'm going to do with the
photographs, I'll announce it at RCM in the future, but I'm not quite
ready yet.

Best wishes,

Chris

On 2008-01-24, Jeff R. wrote:

"DoN. Nichols" wrote in message
...

Out of curiosity -- don't you need something like a
phase-contrast microscope to see the results? I had one at work for

[ ... ]

Nup.
A plain old reflecting microscope will keep you entertained for hours. It
all hinges on good polishing and etching, of course. These 'scopes always
have (and need!) built-in lighting, which operates axially.

Of course. You aren't going to get much illumination through
the metalfrom below. :-)

I don't even know what a phase-contrast microscope *is* ! :-(

It combines light through two paths which results in colors
derived from *very* slight differences in height.

If it does what it sound like it does, then it would be great - yes - but
not necessary.

I would be interested to see what a difference it makes with
polished and etched metal samples. I've only used it on integrated
circuit dice.

I've gone up to pretty impressive magnification(s) with the oil-immersion
lens, too.

O.K. That sounds good enough.

I can't seem to find any connection of phase contrast with
metalurgical with a quick Google search.

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 ---

----- Original Message -----
From: "Christopher Tidy"
Newsgroups: rec.crafts.metalworking
Sent: Friday, January 25, 2008 8:44 AM
Subject: Looking for etched metal specimens



I ought to be able to lay my hands on dilute nitric acid, but it's diluted
in water. My understanding is that the etch needs to be made from nitric
acid in ethanol or methylated spirit. There's also apparently some reason
why you shouldn't store the etch either.

What the effect of trying to etch specimens in dilute nitric acid would
be, I don't know. Would they go rusty? If it works, that would be neat,
because dilute nitric acid is far easier to source.

I admit I'm guessing here, but I don't see (much of) a problem with the
dilute option. The specimen is dried immediately after etching, and remains
in a dry case. I don't think rust would be a problem. Anyways - etching
duration is always a moveable feast, regardless of Nital concentration.

I've spent many an afternoon etching then re-lapping then etching, then
etching again, then re-lapping again (repeat ad infinitum).


See my latest thread on microscopes.

Wilco.


--
Jeff R.