Thermochromic ceramics?

Dog Ma 1

unread,

Nov 3, 2004, 7:25:58 PM11/3/04

to

A friend reports that one of his unglazed teapots changes color slightly
when hot, and that the difference is not due to surface or bulk hydration.

Does anyone here know if clay is known to be thermochromic? If so, is it due
to a mixed-valence charge transfer effect, change in lattice spacing
affecting bandgap, or what?

TIA-

DM

Mark Tarka

unread,

Nov 4, 2004, 9:25:59 AM11/4/04

to

"Dog Ma 1" <spamd...@att.net (reply w/o spam)> wrote in message news:<qGeid.61791$OD2....@bgtnsc05-news.ops.worldnet.att.net>...

> A friend reports that one of his unglazed teapots changes color slightly
> when hot, and that the difference is not due to surface or bulk hydration.

Your friend is obviously has some arcana stuffed
into his brain.

> Does anyone here know if clay is known to be thermochromic? If so, is it due
> to a mixed-valence charge transfer effect, change in lattice spacing
> affecting bandgap, or what?

But he or she don't know clay, eh?

Neither does I, but'd guess the thermal
change isn't enough to affect the optical
characteristics.

Mark (363 more days to go :-)

Uncle Al

unread,

Nov 4, 2004, 10:34:45 AM11/4/04

to

Thermochromic glazes on mugs are routinely available. A particularly
egregious example is a Star Trek transporter that operartes when you
fill the mug with hot liquid.

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz.pdf

Ragnarok

unread,

Nov 5, 2004, 3:53:16 AM11/5/04

to

We've had unglazed ceramics around for over 8,000 years. I think
someone would have noticed it, and the Star Trek gizmo Uncle Al talks
about would have been in use since the time of Caesar.

Iulian

Martin Brown

unread,

Nov 5, 2004, 1:06:50 PM11/5/04

to

In message <418A4C15...@hate.spam.net>, Uncle Al
<Uncl...@hate.spam.net> writes

>Dog Ma 1 wrote:
>>
>> A friend reports that one of his unglazed teapots changes color slightly
>> when hot, and that the difference is not due to surface or bulk hydration.
>>
>> Does anyone here know if clay is known to be thermochromic? If so, is it due
>> to a mixed-valence charge transfer effect, change in lattice spacing
>> affecting bandgap, or what?
>
>Thermochromic glazes on mugs are routinely available. A particularly
>egregious example is a Star Trek transporter that operartes when you
>fill the mug with hot liquid.

I have one sat on the desk in front of me. It came from the Merck
technical centre in the UK and is an iridescent dark grey at room
temperature but clear water white with a hot drink in it revealing their
logo.

It says "Coated with Colorstream(R) Tropic Sunrise" (sic).

The glaze feels like it is a polymer and from the look of it a liquid
crystal technology. Is that a reasonable guess or if not then how is it
done with inorganics?

Regards,
--
Martin Brown

Uncle Al

unread,

Nov 5, 2004, 3:40:42 PM11/5/04

to

The one I saw looked inorganic. I could be wrong. Either way, the
historic and hallowed application would be a bodacious lady having her
garments disappear. We're talking technology augmenting quality of
life here.