Subject: Re: What is this material from soldering iron.

From: [email-masked] (Tim Shoppa)
Date: 6 Jun 1996 06:09:21 GMT

In article <[email-masked]>, Spehro Pefhany <[email-masked]> wrote:
>Damon Brantley ([email-masked]) wrote:
>
>Probably mica sheet, it is used in a lot of heaters that have to operate 
>fairly hot.

I've taken apart several Wellers, and I'm pretty sure that the material
is Mica[

>Where to get it in small quantities, I don't have any idea.
>Vaccum tubes used (use?) little stamped pieces of mica to hold the wires 
>in position. 

I think the US government has an *enormous* stockpile of it, or at
least they did as of a few years ago.  All the result of a shortage
of it in WW2, where it was an important insulator in high-quality
RF capacitors and (as you note) tubes.  The stockpile was one of
the targets of ridicule by some senator or congressperson who was
trying to find waste in the government and military several years
ago, I think.  (Any actually useful material will be greatly mocked
by politicians if it's used in the construction of anything as
"obsolete" as high-voltage tubes and radio equipment.)

Flat pieces of mica are readily available as heat-sink insulators
for semiconductors.  The mica HS insulators that I'm familiar with are
rather brittle and not easily bent tightly, but you might give
the stuff a try.  Radio Shack almost certainly sells both TO-220
and TO-3 heat sink insulators in small quantities.  The lat time
I bought such insulators at Radio Shack they appeared to be mica.

Tim. ([email-masked])

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From: [email-masked] (Kurt Hesse)
Date: Thu, 06 Jun 1996 04:02:59 GMT

[email-masked] (Damon Brantley) wrote:

>        I dissected a soldering iron (out of curiosity) and noticed that some 
>type of non electrical conducting sheet to insulate the heater wire from the 

Snip...

>        Does anyone have any idea what this material might be and where I 
>might be able to purchase some.
>        Thanks.

Definitely sounds like mica.  The stuff used to be very commonly used
to insulate power semiconductors from heatsinks (good thermal
conductivity and dielectric strength).  You might try a heatsink
manufacturer such as Aavid (sp?), Thermalloy, or Wakefield (EG&G).
These will sell you pieces cut for TO-3, TO-220, TO-247 etc.
semiconductor packages.  You could also try Electrical Insulation
Suppliers (EIS) Fabrico division.  I don't know if they handle mica or
not, but they do have things such as kapton and nomex, which both have
excellent high temperature characteristics (though not quite like mica
does).

Kurt

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From: [email-masked] (Spehro Pefhany)
Date: 6 Jun 1996 14:37:04 GMT

Kurt Hesse ([email-masked]) wrote:
[..]
: semiconductor packages.  You could also try Electrical Insulation
: Suppliers (EIS) Fabrico division.  I don't know if they handle mica or

Or just rip apart a toaster.. there are usually a few good sized  sheets 
of mica in there with nichrome ribbon wrapped around them. I'll bet it 
would cost less than the minimum order from most industrial sources. 

--
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Spehro Pefhany                                  "The Journey is the reward"
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From: [email-masked] (Bruce Rowen)
Date: 6 Jun 1996 15:35:50 GMT

>would cost less than the minimum order from most industrial sources. 

I missed the topic of this thread, but it appears someone is looking
for sheet mica?

I've obtained free samples from a supplier (5) 8-1/2 x 11 sheets of
various thicknesses.

Just think of an application and ask for evaluation samples.

-- 
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Scientific Programmer				Array Operations Center
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From: "J. Michael Thompson" <[email-masked]>
Date: Fri, 07 Jun 1996 15:12:37 -0400

Tim Shoppa wrote:
 
> I think the US government has an *enormous* stockpile of it <mica>, or at

You are (unfortunately) quite correct. Now they are after the Helium stockpile. 
They want to take the world's only commercial-scale source of this very useful 
material and just vent it to the atmosphere. Why? Because it makes a great 
sound bite to say: "We aren't going to fight any more wars with zeppelins."

JMT

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From: "John R. Johnson" <[email-masked]>
Date: Mon, 10 Jun 1996 11:54:15 -0500

On Fri, 7 Jun 1996, J. Michael Thompson wrote:
<snip>
> sound bite to say: "We aren't going to fight any more wars with zeppelins."

Of course, they probably neither realize nor care, that venting Helium to
the atmosphere tends to vent it to space!  Helium is so hard to retain in
our gravity well that all the helium we have was found trapped below ground.
John

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From: [email-masked] (Tim Shoppa)
Date: 13 Jun 1996 00:04:26 GMT

In article <[email-masked]>,
>sound bite to say: "We aren't going to fight any more wars with zeppelins."

Here's some more information from the 8 Dec 95 issue of
Bob Park's "What's New" (http://www.aps.org/WN/wn120895.html)

1. APS CALLS FOR HELIUM CONSERVATION! HOT AIR IS NO SUBSTITUTE.

   At its 19 Nov 1995 meeting, the elected Council of the American
   Physical Society adopted a strongly worded statement calling for
   measures to "conserve and enhance the nation's helium reserves." The
   action was prompted by pending legislation that would require the
   nation's helium reserves to be sold off by 2015. In the rush to
   downsize government, the helium program has become a metaphor for
   "boondoggle" among politicians who associate it with blimps and party
   balloons. There is scant awareness of helium's growing cryogenic uses
   -- or its rapid depletion. It's a constituent of natural gas from a
   few "helium-rich" fields in the US. Less than half of the helium is
   needed to meet current demand; the rest is wasted. These fields are
   expected to be depleted in 20 years -- or about when the selloff of
   the federal reserve is completed.

Tim. ([email-masked])

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From: "J. Michael Thompson" <[email-masked]>
Date: Wed, 12 Jun 1996 12:30:24 -0400

> our gravity well that all the helium we have was found trapped below ground.

Which is probably just as well, since otherwise we would all sound like Tiny 
Tim. :-)

JMT

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From: [email-masked] (Al Amaral - SunSoft Engineering)
Date: 12 Jun 1996 20:38:45 GMT

>is Mica

Most likely.  As an aside, if you look at the label on that "sparkle" 
toothpaste your 5 year old uses you'll notice that the sparkles are made 
>from  mica...

Strange, but true.  BTW, My kids no longer use sparkle toothpaste...

--Al Amaral--
-- 
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Al Amaral				  [email-masked]
"G'day, and welcome to All Things Delta.  If it's not Delta, IT'S CRAP!" 
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