I agree with Michael especially in taking guidance from (but not blindly
following) good lab analysis of both the outer possibly pointing mortar and
inner bedding mortar (I don't know much about the use history of natural
cement). I would also suggest trying to find protected areas of pointing
mortar such as immediately below a cornice, a window reveal or behind
shutters to verify the original un-weathered pointing mortar.
Eric Hammarberg
Director of Preservation
Vice President
Thornton-Tomasetti Group
LZA Technology Division
641 Avenue of the Americas
New York, NY 10011
Telephone: 917.661.8160
Fax: 917.661.8161
Mobile: 917.439.3537
email: [log in to unmask]
-----Original Message-----
From: edison [mailto:[log in to unmask]]
Sent: Tuesday, November 29, 2005 7:58 AM
To: [log in to unmask]
Subject: Re: [BP] technical question
Ralph,
Given the age of the building, there is an excellent chance that the
original
mortar is a natural cement/lime blend. A higher lime content could have been
used for the setting mortar, a higher cement content for the pointing,
common
practice for the period as cement was costlier than lime but lime was
considered deficient in weather resistance.
I would send samples of each to a lab that has experience in distinguishing
between the various binders in use during the 1890's and let the results
guide
me. If they determine that there is natural cement then the buff color is
the
cement color and original to the building.
Edison Coatings, Inc.
Michael 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: [log in to unmask]
To: [log in to unmask]
Sent: Tue, 29 Nov 2005 06:59:24 EST
Subject: Re: [BP] technical question
> It's time to put on your conical thimking caps, boys and girls.
>
> Our fearless leader ][<en and I have been working on (the design phase
> of) a project here in Summit, during the course of which the local
> Town Hall, an 1892 buff(ish) to salmon-colored, pressed-brick
> building, will have its butter joints repointed. The original mortar,
> when brick are removed, looks very light colored (I would describe
> it as very pale yellow, or a slightly yellowish white); the mortar
> visible at the faces of the joints has a buff-ish color much closer
> to that of the brick. We didn't see any sign that the buff mortar
> was part of an original pointing job, or part of a repointing, either.
>
> Early (pre-1900) photos show the facade without apparent contrast between
> brick and mortar color, which is what makes me doubt that the pale yellow
> mortar was ever exposed to sight, but nevertheless the pale yellow is
> what we find. The surviving mortar joints, 113 years later, are only
> slightly recessed from the face of the brick, so the lack of contrast
> between brick and mortar can't be blamed on the mortar being darkened
> by shadow lines cast by the brick..
>
> Anybody got any guidance for me on how to choose between mortar that looks
> too light,as opposed to mortar that doesn't match the (interior)
> sample but looks right? I am scared to death to call for the pale
> yellow mortar and have the building wind up looking like there are
> neon lights in the mortar joints, but that seems to be what the
> mortar samples show.
>
> Thanks.
>
> Ralph
------- End of Original Message -------
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