[Clayart] Clayart Digest, Vol 50, Issue 43

ronroy at ca.inter.net ronroy at ca.inter.net
Sun Feb 2 12:04:50 EST 2020


There is no reason we can't test to see what will work. We all have  
freezers! A freeze thaw test could be done every day to see what would  
work. We could even call it science.

RR


Quoting Robert Harris <robertgharris at gmail.com>:

> I clearly remember back in the 80s 90s (and for all I know, now), they used
> to sell ?frost-proof? terra-cotta plant pots in the UK. The cheap ones used
> to crack regularly when it froze ... probably a combination of water
> freezing in the clay, as well as some pressure from the frozen water inside
> the pot.
>
> I?m not sure if they were an underfired red stoneware, or a terracotta with
> some fireclay added that was fired hotter than normal, but they certainly
> worked. They were also quite a bit more expensive, but certainly not so bad
> that they didn?t end up taking over the market.
>
> There is quite a fun little video out out by one of the makers of very
> fancy terracotta plant pots in the UK. At the beginning of the video there
> is a little bit about how they blend their clay, although it?s rather less
> than specific!
>
> https://youtu.be/9ALR6QV0kkw
>
>
> R
>
> On Fri, Jan 31, 2020 at 9:02 PM <vpitelka at dtccom.net> wrote:
>
>> Hi Alice -
>> It can't just be an open claybody.  According to Val Cushing, it must be a
>> claybody with enough porosity that also has enough mechanical strength to
>> withstand the pressure of the expanding freezing water.  That's why an
>> underfired highfire body works well.  Fired earthenware is an open
>> claybody, but it has little mechanical strength and will disintegrate in a
>> hard freeze.
>> - Vince
>>
>> Vince Pitelka
>> Professor Emeritus of Art/Ceramics
>> Appalachian Center for Craft
>> School of Art, Craft & Design
>> Tennessee Tech University
>> Now Residing Chapel Hill, NC
>> vpitelka at dtccom.net
>> www.vincepitelka.com
>>
>> -----Original Message-----
>> From: Clayart <clayart-bounces at lists.clayartworld.com> On Behalf Of Alice
>> DeLisle
>> Sent: Friday, January 31, 2020 11:34 AM
>> To: via Clayart <clayart at lists.clayartworld.com>
>> Subject: Re: [Clayart] Clayart Digest, Vol 50, Issue 43
>>
>> Ric,
>>
>> Val Cushing wrote about this in Cushing?s Handbook. Most potters assume
>> that the best clay body for outdoor work is the one with the lowest
>> absorption. According to Val?s article (and the ceramic engineers at
>> Alfred) the reason that outdoor work breaks is that any absorbed water
>> expands and contracts with freezing and thawing. Most clays absorb some
>> water. An open clay body allows space for the water to expand and contract
>> and is thus actually better for outdoor work than a closed clay body. The
>> article includes an absorption test for outdoor work. The Handbook is
>> available from the Pharmacy (book store) at Alfred University. I could send
>> a copy of the short article if there is interest.
>>
>> Peter King wrote a related article entitled something like ?Another Cup of
>> Grog, Please?. A bit tongue in cheek!
>>
>> Alice
>>
>> Alice DeLisle
>>
>> wanderland at att.net
>> https://www.facebook.com/IslandTexturesAliceDeLisle/
>> https://www.flickr.com/photos/alice_delisle/sets/
>>
>> "Not all those who wander are lost?" ? J.R.R.Tolkien
>>
>>
>>
>> > On Jan 31, 2020, at 4:29 AM, clayart-request at lists.clayartworld.com
>> wrote:
>> >
>> > Date: Fri, 31 Jan 2020 00:31:40 +0000
>> > From: Ric Swenson <ricswenson0823 at hotmail.com <mailto:
>> ricswenson0823 at hotmail.com>>
>> > To: Clayart international pottery discussion forum
>> >       <clayart at lists.clayartworld.com <mailto:
>> clayart at lists.clayartworld.com>>
>> > Subject: Re: [Clayart] Best clay for outdoor sculpture
>> > Message-ID:
>> >       <
>> HK0PR03MB3956E18D2824624EB0CA542EC3070 at HK0PR03MB3956.apcprd03.prod.outlook.com
>> <mailto:
>> HK0PR03MB3956E18D2824624EB0CA542EC3070 at HK0PR03MB3956.apcprd03.prod.outlook.com
>> >>
>> >
>> > Content-Type: text/plain; charset="windows-1252"
>> >
>> > IMHO....A clay body that is vitrified (glass-like) to the highest
>> temperture possible without deforming or bloating will last the longest
>> outdoors. Freezing and thawing in a body that is not vitrified well will
>> cause it to deteriorate over time.
>> >
>> > A coating of vitrified glaze will allow an outdoor sculpture to last
>> much longer.  Common brick clay (Terracotta) that is fired too low will
>> deteriorate over time...by spalling, flaking or erosion of the surface.
>> >
>> > The addition of grog to a sculpture body helps with drying without
>> cracking but as long as the body is fired to high enough temp. it should be
>> fine. A fired body with less than 1 % water absorbsion would be desirable.
>> >
>> > Other thoughts folks?
>> >
>> > Regards,
>> >
>> > Ric
>> >
>> > ________________________________
>> > From: Clayart <clayart-bounces at lists.clayartworld.com <mailto:
>> clayart-bounces at lists.clayartworld.com>> on behalf of Scary Potter <
>> scary.potter at yahoo.com <mailto:scary.potter at yahoo.com>>
>> > Sent: Friday, January 31, 2020 1:54 AM
>> > To: clayart at lists.clayartworld.com <mailto:
>> clayart at lists.clayartworld.com> <clayart at lists.clayartworld.com <mailto:
>> clayart at lists.clayartworld.com>>
>> > Subject: [Clayart] Best clay for outdoor sculpture
>> >
>> > Looking for suggestions from some of you fabulous experts - best Clay
>> for cone 5-6 garden art?
>> > What attributes should a clay body have for surviving outdoors?  More
>> ?open?, more grog, less something? Do you have a favorite recipe or
>> commercially available body you love?
>> > I?ve only made small things with smooth clay but want to venture into
>> larger garden sculptures this spring.
>> > I normally fire to cone 5 or 6.
>> >
>> > S.Cary -
>> > Make something beautiful every day.
>> > Scarypotter.com <http://scarypotter.com/>
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Ron Roy
ronroy at ca.inter.net
Web page ronroy.net




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