When you knead dough to make bread you fold it over and over.....often
if you cut through it you can see lines. same with ceramics. The more
the clay matrix is mixed the smoother the matrix becomes- fewer lines.
This would not be the case for ceramics which are poured into molds in
liquid form where instead of layers pressed together one gets air
bubbles. I suppose one could build up a piece with many pourings- that
would create the lines-like layers in a pastrey but not as pronounced.
Benjamin Carter wrote:
> All,
>
> I love the idea of using the fracture patterns from
> frost/rain/salt/other split pottery to get more information about the
> formation of the paste or matrix of a ceramic. I would think that this
> would be fairly complicated. It would seem that breaks for hand built
> coiled pottery would be fairly obvious, but what can we see from
> industrial products such as creamware? I'd love to hear what you all
> have to say. As I mentioned before I have a large number of very tiny
> fragments which don't tell me much more than the basics. Any way to
> get more information would be wonderful.
>
> Cheers,
> Ben
>
> On 11/12/2010 12:12 PM, David Legare wrote:
>
>> See Mark's comment below. The addition of water to the paste from
>> the processes
>> he mentions will also cause that kind of spalling or "potlidding" in the
>> ceramics. It is the same thing that happens to cherts and
>> chalcedonies with
>> enough heat. I suspect that scratches in the glaze or unglazed
>> portions of the
>> material will allow that kind of water seepage.
>>
>>
>>
>> ----- Original Message ----
>> From: Conrad Bladey<[log in to unmask]>
>> To: [log in to unmask]
>> Sent: Fri, November 12, 2010 9:55:48 AM
>> Subject: Re: split ceramics
>>
>> the differential effect of freeze thaw upon "pastes" or clay bodies may
>> be one way of separating what would be otherwise plain undistinguishable
>> wares.
>> Given similar conditions some would and some would not. However this
>> could have to do with the way the particular batch of mix was blended.
>> Like bread dough when kneeding striations develope as in muscle. Between
>> the strands the water gets in then freezes then pops.. With more mixing
>> some wares may resist even though they look the same. They may not come
>> off in layers but in other ways.....never resist an opportunity to
>> "split"
>>
>> Susan Walter wrote:
>>
>>> Yes, I have encountered those too; but not at this site. These are
>>> split right down through the paste, with each side piece one side
>>> glazed the other "raw."
>>>
>>> This site also has some of the typically melted and discolored surface
>>> glaze from the burn.
>>>
>>> Anyway, what satisfies me is every one responding says it is a
>>> natural, and not really uncommon phenomenon.
>>>
>>> Thanks everyone!
>>>
>>>
>>> ----- Original Message ----- From: "Patrice L. Jeppson"
>>> <[log in to unmask]>
>>> To:<[log in to unmask]>
>>> Sent: Thursday, November 11, 2010 6:26 PM
>>> Subject: Re: split ceramics
>>>
>>>
>>>> I have seen ceramic fragments at the site of an early 19th C house
>>>> fire
>>>> that exhibited substantial spalling. The fragments looked pockmarked.
>>>>
>>>> On 11/11/2010 10:49 AM, Susan Walter wrote:
>>>>
>>>>> Not at all near salt water; inland a 2 hour drive from the ocean.
>>>>> And
>>>>> the locus is on a low hillside with an intermittant stream a few
>>>>> hundreds of feet away.
>>>>>
>>>>> One thing I did not mention was this particular site is supposed to
>>>>> have existed less than 3 years, and was burned out. And there have
>>>>> been wildfires through the area for hundreds of years, though it was
>>>>> spared that during the last few years of our infernos.
>>>>>
>>>>> Has anyone seen this splitting/spalling effect as a result of fire?
>>>>>
>>>>> ----- Original Message ----- From: "Benjamin Carter"
>>>>> <[log in to unmask]>
>>>>> To:<[log in to unmask]>
>>>>> Sent: Wednesday, November 10, 2010 4:29 PM
>>>>> Subject: Re: split ceramics
>>>>>
>>>>>
>>>>>> Susan and other Histarchers,
>>>>>>
>>>>>> Could it be salt water getting into the sherd? When salt water
>>>>>> dries,
>>>>>> the formation of crystals can cause ceramics to spall/split.
>>>>>>
>>>>>> Nearly all of my white earthen ware ceramics from a coastal Maine
>>>>>> site
>>>>>> (c. 1800) were split. I think it was due to a combination of
>>>>>> freeze/thaw
>>>>>> cycles and salt water. At this point most are from relatively
>>>>>> close to
>>>>>> the surface.
>>>>>>
>>>>>> Ben Carter
>>>>>>
>>>>>> On 11/10/2010 6:18 PM, Susan Walter wrote:
>>>>>>
>>>>>>> Hmmm, the site is in San Diego County...
>>>>>>>
>>>>>>> ----- Original Message ----- From: "Mark Branstner"
>>>>>>> <[log in to unmask]>
>>>>>>> To:<[log in to unmask]>
>>>>>>> Sent: Wednesday, November 10, 2010 11:40 AM
>>>>>>> Subject: Re: split ceramics
>>>>>>>
>>>>>>>
>>>>>>>> Susan,
>>>>>>>>
>>>>>>>> I don't know what part of the country that you're working in, but
>>>>>>>> "frost spalling" is a relatively common phenomenon ...
>>>>>>>>
>>>>>>>> Essentially, moisture gets into the porous fabric of the
>>>>>>>> pottery and
>>>>>>>> it splits the pottery when it freezes during the winter. It
>>>>>>>> certainly does not happen all the time, but it does occur with
>>>>>>>> some
>>>>>>>> regularity. Sometimes just the glaze spalls off the fabric,
>>>>>>>> but the
>>>>>>>> fabric itself can split.
>>>>>>>>
>>>>>>>> Mark
>>>>>>>>
>>>>>>>>
>>>>>>>>> Nov. 10, 2010
>>>>>>>>>
>>>>>>>>> Hello all,
>>>>>>>>>
>>>>>>>>> I have a site with several sherds of transferware that are
>>>>>>>>> split so
>>>>>>>>> that there is a transferware / glazed surface on one side and the
>>>>>>>>> paste interior on the other side.
>>>>>>>>>
>>>>>>>>> This makes them about 1/8 inch thick. They tend to be about 1
>>>>>>>>> inch
>>>>>>>>> long, and about 3/4 inch wide.
>>>>>>>>>
>>>>>>>>> The edges are not shaped; in "plan" view the pieces are
>>>>>>>>> miscellaneously trapezoidal.
>>>>>>>>>
>>>>>>>>> In appearance they somewhat remind me of porcelain pin
>>>>>>>>> trays/childrens toy tea trays that are decorated and glazed on
>>>>>>>>> the
>>>>>>>>> top and bisque on the bottom, except these transfer pieces are
>>>>>>>>> not
>>>>>>>>> smoothly finished on the bottom ("bisque") like the porcelain
>>>>>>>>> items
>>>>>>>>> are.
>>>>>>>>>
>>>>>>>>> I do not think these were made intentionally.
>>>>>>>>>
>>>>>>>>> I've not seen so many of these at one site before. Has anyone
>>>>>>>>> knowledge of what did this?
>>>>>>>>>
>>>>>>>>> Thanks every one,
>>>>>>>>>
>>>>>>>>> S. Walter
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> --
>>>>>>>>
>>>>>>>> Mark C. Branstner, RPA
>>>>>>>> Historic Archaeologist
>>>>>>>>
>>>>>>>> Illinois State Archaeological Survey
>>>>>>>> Institute of Natural Resource Sustainability
>>>>>>>> University of Illinois at Urbana-Champaign
>>>>>>>> 209 Nuclear Physics Lab, MC-571
>>>>>>>> 23 East Stadium Drive
>>>>>>>> Champaign, IL 61820
>>>>>>>>
>>>>>>>> Phone: 217.244.0892
>>>>>>>> Fax: 217.244.7458
>>>>>>>> Cell: 517.927.4556
>>>>>>>> [log in to unmask]
>>>>>>>>
>>>>>>>>
>>>>>>>> When you think of that perfect retort five minutes after the
>>>>>>>> conversation is over - that's when you're:
>>>>>>>>
>>>>>>>> "... bursting with the belated eloquence of the inarticulate
>>>>>>>> ..."
>>>>>>>>
>>>>>>>> Edith Wharton in the "The Age of Innocence"
>>>>>>>
>>>>>>>
>>>>>>>
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>>>>>>>
>>>>>>>
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>>>>>>> Version: 9.0.869 / Virus Database: 271.1.1/3248 - Release Date:
>>>>>>> 11/09/10 23:34:00
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>>>>>
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>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
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>>>
>>>
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>>>
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>>> Checked by AVG - www.avg.com
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>>
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>>
>>
>
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