Steve Slatin on wed 5 mar 08
Gayle --
Were it true, thermos bottles would be lined with
matte glazes.
They are not.
There are lots of strange things about thermal
conductivity (sapphires conduct heat
differently depending on how they are aligned,
for example), metals are pretty easy, but
non-metal crystals often depend on something
called 'phonon carriers.' The science is
rather daunting.
What isn't is your ability, as a potter, to test
the hypothesis. One pot of boiling water,
two essentially identical mugs (or bowls)
at room temperature, one glossy glazed,
the other matte, pour the water into the
bowls at the same time, and see
what the difference is in external temp
on the mugs after a given amount of
time.
I tried it, with a pair that were one
matte inside and out, and the other
glossy inside and out -- I didn't have
a mechanism to test for temp, but
'by hand' they seemed about the
same after five minutes. This would
be a great thing for someone with
one of those neat non-contact
thermometers to check.
-- Steve Slatin
gayle bair wrote:
A potter friend of mine asked if I'd post this query to Clayart....
"Question for glaze gurus: I recently heard from someone that
considers himself an expert in everything related to clay that pots
that are made to hold hot liquids, such as mugs and teapots, should be
lined with a matt glaze. According to him this is because the matt
glaze liner prevents the heat from transferring to the outside of the
pot.
My questions: I have no expertise, but my gut reaction is that this
doesn't make sense. Has anyone heard of this? Does this make sense to
you? Aren't matt glazes more likely to leach - something that I
certainly don't want for a pot that someone that will ingest the
liquid in the container?"
TIA & I'll forward the answers.
Gayle Bair
---------------------------------
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gayle bair on wed 5 mar 08
A potter friend of mine asked if I'd post this query to Clayart....
"Question for glaze gurus: I recently heard from someone that
considers himself an expert in everything related to clay that pots
that are made to hold hot liquids, such as mugs and teapots, should be
lined with a matt glaze. According to him this is because the matt
glaze liner prevents the heat from transferring to the outside of the
pot.
My questions: I have no expertise, but my gut reaction is that this
doesn't make sense. Has anyone heard of this? Does this make sense to
you? Aren't matt glazes more likely to leach - something that I
certainly don't want for a pot that someone that will ingest the
liquid in the container?"
TIA & I'll forward the answers.
Gayle Bair
Tucson AZ
Bainbridge Island WA
gayle@claybair.com
www.claybair.com
Ivor and Olive Lewis on thu 6 mar 08
Dear Gayle Bair,=20
Relating to << pots that are made to hold hot liquids, such as mugs and =
teapots, should be
lined with a matt glaze. According to him this is because the matt glaze =
liner prevents the heat from transferring to the outside of the pot.>>
I would like that self appointed "Expert" to explain the Physical =
process which retards the transmission of heat, or ask what gives a Mat =
glaze its insulating properties.
I would counter this proposition by suggesting the because a mat glaze =
has a greatly enlarged surface area over a mirror bright glaze that it =
will adsorb a greater quantity of heat and cause the beverage to cool =
rapidly.
My own opinion is that Mat glazes should be avoided for lining pots =
because they are difficult to clean=20
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Linda Rosen on thu 6 mar 08
Gayle,
My gut reaction seconds yours. This makes no sense-- even less than no
sense. I'd say that the opposite would be more likely to be true. Glossy
liner glazes are more likely to be properly fired and durable and less
liable to leach . My understanding is that this is especially true at =
cone 6
. Liner glazes should not leach, this trumps any "heat transfer" =
suggestion
(which also seems dubious)
"Question for glaze gurus: I recently heard from someone that
considers himself an expert in everything related to clay that pots
that are made to hold hot liquids, such as mugs and teapots, should be
lined with a matt glaze. According to him this is because the matt
glaze liner prevents the heat from transferring to the outside of the
pot.
Bruce Girrell on thu 6 mar 08
Gayle Bair wrote:
>... clay that pots that are made to hold hot liquids, such as mugs and
teapots,
> should be lined with a matt glaze ... because the matt
> glaze liner prevents the heat from transferring to the outside of the
> pot.
As someone else wrote here recently: male bovine excrement!
Whether or not a glaze is matte has essentially zero relationship with its
thermal conductivity.
Even if it were a good thermal insulator (which it isn't!), the glaze layer
is so thin that it would have little effect.
Listen to your intuition.
Bruce Girrell
Kelly Johnston on thu 6 mar 08
I've been meaning to post a similar question but from the other
angle! The instruction I got at art college was that a matte glaze
should NOT be used as a liner on anything holding hot liquids. I was
told the reason the glaze is matte, is that it is rough and sort of
crater like and traps small particles of whatever its holding, which
can then be released the next time it is filled with hot liquid.
I believed this after some friends commmented on a set of mugs I'd
bought them as a gift before I'd heard this. They were lined with a
matte glaze, and they stopped using them after a short time, as they
found that their coffee tasted bad in those mugs. My lecturer
suggested they might be able to get rid of the bad taste if they ran
the mugs thru a dishwasher regularly, but they didn't own one, so the
mugs were packed away. I was embarrassed to have given such a useless
gift! I think it's worse here in Australia where the vast majority
of people have milk in their coffee and tea. If it's a clear liquid
it might be ok, but I won't use a matte liner glaze after that
experience.
I've been surprised to see many potters using matte liner glazes as
I've been surfing various websites, and wondered if this was some
sort of isolated incident, or if there is any general concesus on
this question. I'm looking forward to seeing what other replies you
get, Gayle!
Kelly in Emerald, Qld Australia
Trying to stay muddy to keep the sandflies at bay!
gayle bair on thu 6 mar 08
Hi Kelly,
Good question! I think the answer is whether the
glaze is fired to temperature or under-fired.
I'll be interested to see what answers you get
from our gurus.
Best regards.
Gayle Bair - in sunny warm & chilly Tucson AZ
Bainbridge Island WA
gayle@claybair.com
www.claybair.com
On Mar 5, 2008, at 10:40 PM, Kelly Johnston wrote:
> I've been meaning to post a similar question but from the other
> angle! The instruction I got at art college was that a matte glaze
> should NOT be used as a liner on anything holding hot liquids. I was
> told the reason the glaze is matte, is that it is rough and sort of
> crater like and traps small particles of whatever its holding, which
> can then be released the next time it is filled with hot liquid.
>
> I believed this after some friends commmented on a set of mugs I'd
> bought them as a gift before I'd heard this. They were lined with a
> matte glaze, and they stopped using them after a short time, as they
> found that their coffee tasted bad in those mugs. My lecturer
> suggested they might be able to get rid of the bad taste if they ran
> the mugs thru a dishwasher regularly, but they didn't own one, so the
> mugs were packed away. I was embarrassed to have given such a useless
> gift! I think it's worse here in Australia where the vast majority
> of people have milk in their coffee and tea. If it's a clear liquid
> it might be ok, but I won't use a matte liner glaze after that
> experience.
>
> I've been surprised to see many potters using matte liner glazes as
> I've been surfing various websites, and wondered if this was some
> sort of isolated incident, or if there is any general concesus on
> this question. I'm looking forward to seeing what other replies you
> get, Gayle!
>
> Kelly in Emerald, Qld Australia
> Trying to stay muddy to keep the sandflies at bay!
>
> ______________________________________________________________________________
> Clayart members may send postings to: clayart@lsv.ceramics.org
>
> You may look at the archives for the list, post messages, change your
> subscription settings or unsubscribe/leave the list here: http://www.acers.org/cic/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at melpots2@visi.com
Veena Raghavan on thu 6 mar 08
Hi Kelly,
A suggestion for your friends, if they want to give those mugs another try,
is to clean them with a paste of baking soda and white vinegar. You apply the
paste to the inside of the mug, let is stay on for a few hours, and scrub off
with a scrubber. This removes all the residue and makes the inside of the mugs
as good as new. No bad taste and looks great.
Just a thought.
Veena
In a message dated 3/6/2008 3:15:28 PM Eastern Standard Time,
geoffandkelly@HOTMAIL.COM writes:
>
> I believed this after some friends commmented on a set of mugs I'd
> bought them as a gift before I'd heard this. They were lined with a
> matte glaze, and they stopped using them after a short time, as they
> found that their coffee tasted bad in those mugs. My lecturer
> suggested they might be able to get rid of the bad taste if they ran
> the mugs thru a dishwasher regularly, but they didn't own one, so the
> mugs were packed away. I was embarrassed to have given such a useless
> gift! I think it's worse here in Australia where the vast majority
> of people have milk in their coffee and tea. If it's a clear liquid
> it might be ok, but I won't use a matte liner glaze after that
> experience.
VeenaRaghavan@cs.com
Jim Bob Salazar on thu 6 mar 08
on the matt liner glaze realm...
i have made hundreds of beer mugs for the local brew pup here in alpine. in
the development of the project we actually tested several glazes for liners.
someone earlier mentioned the about of surface area in a matt glaze being
greater...our testing fount that the micro brew reacted with the texture of
the matt surface. a matt surface is very textural and had millions of
surface pits that caused the beer to foam violently. it was very hard to
fill up on the mugs glazed with the matt glaze. the glossy surface harbors
no air and the beer was much easier to get into the mugs.
thanks for listening,
jim bob
Jim Bob Salazar
Associate Professor of Art - Ceramics
Sul Ross State University
P.O. Box C - 43
Alpine, Texas 79832
432.837.8405 office
432.837.8280 studio
www.cone10potter.com
"No hurry - no worry" - Otto Heino
Lee on thu 6 mar 08
Maybe ITC? Anybody lemon test it? ;^)
--
Lee, a Mashiko potter in Minneapolis
http://mashikopots.blogspot.com/
"I would love to live like a river flows, carried by the surprise of
its own unfolding." -- John O'Donohue
Miles Smith on fri 7 mar 08
I thought that glass is listed as an insulator to heat. I thought that made
since; silica is hard to melt in a glass furnace.
Would be nice to hear from someone who has a temp. probe. Measure the temp.
of the outside of a thick glass pan holding boiling water. I know thick
window glass keeps the cold out and the furnace heat in at my house.
Miles Smith
----- Original Message -----
From: "Lee"
To:
Sent: Thursday, March 06, 2008 1:24 PM
Subject: Re: Question regarding Matt Liner Glazes
> Maybe ITC? Anybody lemon test it? ;^)
> --
> Lee, a Mashiko potter in Minneapolis
> http://mashikopots.blogspot.com/
>
> "I would love to live like a river flows, carried by the surprise of
> its own unfolding." -- John O'Donohue
>
> ______________________________________________________________________________
> Clayart members may send postings to: clayart@lsv.ceramics.org
>
> You may look at the archives for the list, post messages, change your
> subscription settings or unsubscribe/leave the list here:
> http://www.acers.org/cic/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots2@visi.com
>
Leigh Whitaker on fri 7 mar 08
I keep reading this post as "Matt Lauer glazes". That makes no sense.
Leigh Whitaker
visit my etsy shop at leighwhitaker.etsy.com
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