JUST BY COINCIDENCE, IT WAS CRACK-MONITORING DAY AT THE HYDE PARK BARRACKS
MUSEUM (SYDNEY) SO AS WE MEASURED, WE TALKED ABOUT THE VARIOUS WAYS WE HAD
ATTEMPTED TO MEASURE CRACKS IN HISTORIC HOUSES. THE RESULTS OF OUR
CONVERSATION:

1. THE GLASS SLIDE TELL-TALE (FIXED AND/OR OVERLAPPED)

2. CALIBRATED METAL GAUGES THAT ARE FASTENED TO TWO SIDES
OF A CRACK AND MEASURE MOVEMENT IN ONE PLANE ONLY

3. A THREE-POINT SET OF MONITORING PINS THAT ARE PERIODICALLY CALIBRATED
FOR MOVEMENT IN MORE THAN ONE DIMENSION (WHAT WE USE NOW...)

4. PHOTOGRAPHY FROM A DISTANCE, PHOTOGRAPHY FROM CLOSE-UP, THEN USED FOR
CONTRAST AND COMPARE

5. THE TEDIOUS CRACK MAP, IN WHICH WE DRAW THE CRACKS AND SHOW CONTINUING
MEASUREMENTS FROM FIXED POINTS

6. THE MARKING OF THE LIMITS OF CRACKS WITH PENCIL, THEN FOLLOW-UP

THEN THERE WERE TWO MORE WE DREAMED UP WHILE UP THE LADDER:

A. WHAT ABOUT CRACK RUBBINGS DONE IN THE TRADITIONAL BRONZE RUBBING METHOD?

B. WHAT ABOUT USING THOSE LASER LIGHT MEASURING THINGS THAT ARCHITECTS AND
SURVEYORS SEEM TO FAVOUR. MEASURE THE WALL FROM A FIXED POSITION OPPOSITE
THE CRACK TO GET THE MOVEMENT OF THE WALL IN ANOTHER DIMENSIONAL PLANE...

But frankly, the problem with all of these measuring techniques seems to be
in their limitation of gauging the movement in the plane of the wall. We
HAVE found that we need to know the cyclical movement on the wall in and
out to make a through assessment of the problems (if any).

Michael Bogle
Historic Houses Trust of NSW
Sydney, Australia


>I work in a historic house museum that is beginning to show large cracks in
>the plaster.  Some of these have developed due to settling, others, due to
>poeople touching the walls ("look at the hole in the wall...").  Does any one
>have any idea of a product that will help monitor the growth of these cracks.
> I once saw a product at the Octagon House in Washington, DC- they looked
>like "bandaide" that attached to the wall and was calibrated.  Any other
>ideas.  I thought it would also be a great way to educate our visitors about
>historic preservation/restoration in a site like ours, so it does not bother
>me to have something show.
>
>You can email me at [log in to unmask]
>
>Thanks for any ideas.
>
>Elizabeth Walker
>Curator
>Molly Brown House Museum
>
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Mike Bogle & Peta Landman & Ariel Bogle
429 Riley Street
Surry Hills, Sydney
Australia 2010
(61) (2) 9212 7069