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"
>>>
>>>
>>> -------------------------------------------------------------------------------- 
>>>
>>>
>>>
>>>
>>>
>>> No virus found in this incoming message.
>>> Checked by AVG - www.avg.com
>>> Version: 9.0.869 / Virus Database: 271.1.1/3248 - Release Date:
>>> 11/09/10 23:34:00
>>>
>
>
> -------------------------------------------------------------------------------- 
>
>
>
>
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 9.0.869 / Virus Database: 271.1.1/3250 - Release Date: 
> 11/10/10 23:34:00
>
>
>