Dorrin K Mace, Horologost

Dorrin K Mace, Horologost
The Clock Man in a pensive moment

Tuesday, March 27, 2012

Proper care for clock cases

Many times a customer will stop in the shop and ask how to care for their clock case properly.   In this article we look as how a clocks environment affects it and damage that can ensue.

Temperature and Humidity
    WOOD CASES- Since wood is a porous material, it readily absorbs water when humidity levels are high.  The absorption of moisture causes swelling of the wood.  Conversely, wood shrinks in a dry environment.  The shrinking of the wood leads to the formation of structural cracks, lifting of veneers and inlays, gaps in joints, and adhesives becoming brittle.  Fluctuations in temperature and humidity result is an alligator type finish and similar problems.  While precise control of temperature and humidity is desirable, it is not always practical in a home environment.  Damage can be minimized by avoiding extremes in humidity and temperature swings.  This can be accomplished by insuring wooden clocks are kept out of direct sunlight, away from heat sources and out of hot attics, damp basements and unheated out buildings.
    METAL CLOCK CASES- The greatest cause of damage to metal is corrosion.  Corrosion is brought on by the presence of pollution or salts such as those present in the oil of human hands.  Salts and pollution in combination with moisture can produce corrosion.  When dust is allowed to accumulate on the surface of a metal object it attracts moisture thus increasing the rate at which corrosion formation occurs.  Keeping metal objexts clean and free from dust can reduce this problem.  In general, maintaining low humidity levels in area where metal objects are stored or displayed can effectively slow down the rate of corrosion formation.  The recommended temperature and humidity levels for metals is 68 degrees farenheit and 30 percent relative humidity.  However clocks that are constructed of a variety of metals such as wood, ivory or tortoiseshell should be kept under slightly higher humidity levels than those recommended for wooden case clocks.
    PAINTED METAL CLOCK FACES- In environments where humidity levels are high, corrosion can form between the paint layer and its metal support.  When corrosion develops underneath the paint layer, it actually pushes the paint film off of the surface of the clock face.  Once again, the best way to prevent the damage is by providing a stable and moderate humidity level for the clock.  The recommended temperature and humidity levels for the storage and display of wooden clocks are as follows:
WINTER                                                      SUMMER
Temp 70 degrees F                                        Temp 70-75 degree F
Rel Humidity 35-50%                                    Rel Humidity 40-60%
Inexpensive humidity indicators can be purchased from your local hardware store.

    LIGHT LEVELS- Wood finishes, stains and some paints are susceptible to darkening and fading from exposure to high light levels.  For this reason pained or varnished clocks should be shown and stored in an area where exposure to bright light is minimal.  Excessive light can also accelerate the aging and degradation of finishes resulting in a cracked, brittle, or alligatored appearance.  Heat generated from high light levels can also be a factor is causing damage to finishes.  Some can become soft and sticky when temperatures are high.  Soft finishes attract dirt easily and can become stuck to surfaces when left in contact for extended periods of time.
    PEST DAMAGE- Carpet beetles generally exist on protein based materials that are often present is adhesives on clock cases.  Carpet beetles are generally found in the joinery and around the inside of clock cases.  The presence of tiny black beetles (the size of a pin head), small worms or furry carcasses are an indication of infestation.
Powder post beetles characteristically bore small holes (the size of a pin head) into wooden materials.  These holes are generally the first visible evidence of infestation.  Wooden objects should be routinely moved and examined for infestation.  The underside of legs and drawers should be inspected since insects generally hide in inconspicuous, dark places.  If evidence of infestation is found, the object needs to placed in a plastic bag and isolated until it can be examined by a professional conservator.

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