Wow, preservation content!

Having worked on hundreds of terra cotta buildings in every kind of climate,
I have become convinced that freeze-thaw has little to do with typical
glazed brick or terra cotta damages. The same things happen to terra cotta
in San Francisco, Florida and Hawaii where it never freezes, as in New York
or Cleveland or Boston with lots of freeze-thaw cycles, or in Northern
Minnesota or Alberta which is just plain freeze all winter with no thaw.

Nevertheless, my understanding of freeze-thaw testing is that it takes
multiple cycles to get results, and that freezing is done under saturated
conditions. Results can be sketchy and hard to reproduce, I am told. I have
seen data for 60-200 cycles of testing presented to provide comparisons
between different materials.

As for getting things saturated, we would normally start by oven-drying the
piece to establish what "dry" is, which involves leaving it in there and
weighing it periodically until the weight doesn't go down any more. Then
immerse the thing in water and keep weighing it periodically until the
weight doesn't go up any more. Some pieces may take weeks to become
saturated. Some are soaked in an hour.

Edison Coatings, Inc.
M. P. Edison
President
3 Northwest Drive
Plainville, CT 06062
Phone: (860) 747-2220 or (800)697-8055
Fax: (860)747-2280 or (800) 697-8044
Internet: www.edisoncoatings.com
E-Mail: [log in to unmask]

---------- Original Message -----------
From: Met History <[log in to unmask]>
To: [log in to unmask]
Sent: Wed, 9 Jul 2003 15:29:05 EDT
Subject: brick soaking

> I have a fragment of a white glazed brick.  I am soaking it in water,
>  and ultimately want to freeze it to see if the absorbed water will
> fracture the brick.
>
> 1.      I don't notice any bubbles coming up.   Does brick not
> absorb water in this fashion?
> 2.      How long should I wait?
> 3.      Once the water is absorbed, will freezing actually produce
> the desired results?   Or should I just use a hammer?
>
> Christopher
------- End of Original Message -------

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