Many metrology and visual inspection workshops only focus on collision protection when storing ZHHIMG® precision granite surface plates, ignoring hidden deterioration caused by humidity and light. Although granite undergoes stress relief aging and nano-level precision lapping, there are still tiny capillary pores inside the stone. In humid environments, water vapor carries soluble salts and alkalis and migrates to the plate surface through micropores. After water evaporates, salts precipitate and form white efflorescence spots. Long-term illumination accelerates the aging of surface minerals of granite, resulting in yellowing, graying and uneven gloss discoloration. Efflorescence and discoloration are not merely cosmetic defects. Salt crystal expansion continuously damages the lapped reference surface and changes the optical reflection characteristics of the plane, directly interfering with measurement stability of AOI, CMM and visual inspection equipment. Systematic storage management with moisture-proof and light-shielding measures is the core way to prevent efflorescence and discoloration on plate surfaces.
1. Understand the formation of efflorescence and discoloration and identify storage risks
Efflorescence is essentially a process where water acts as a carrier, transporting soluble salts and alkaline substances inside stone micropores to the surface for crystal precipitation. Warehouse condensation, ground moisture and humid air continuously penetrate the bottom and sides of the slab. Condensation caused by day-night temperature difference repeatedly drives alkaline substances to migrate toward the working surface, forming white spots and frosty white bloom. Long-term illumination, especially ultraviolet rays in sunlight, gradually alters the mineral structure on the granite surface, fading the originally uniform black reference plane and producing uneven color patches.
Different from ordinary decorative stone, the lapped surface of precision granite plates serves directly as the metrological benchmark. Efflorescence crystals expand and enlarge micropores and cause surface powdering. Micro-concavities and convexities in stained areas alter optical reflection, generating noise and abnormal contrast during image capture for visual inspection. Even mild efflorescence will affect measurement results of the whole equipment.
2. Control warehouse humidity to cut off water channels triggering efflorescence
Water is the prerequisite for efflorescence. The relative humidity of storage space should be maintained steadily between 40% and 60%. Avoid positions close to exterior walls prone to condensation, basements and areas around cooling towers or condensate pipes.
The plate bottom shall not contact the ground directly. Use original support pads to elevate the slab and isolate capillary moisture rising from the floor. Moisture-proof base plates can be laid on the ground. Desiccants may be placed in storage zones and replaced regularly. During plum rain and high-humidity seasons, close warehouse doors and windows and use dehumidifiers to reduce ambient humidity.
Never let the plate bottom stay in contact with damp floors for a long time. Once the bottom absorbs sustained moisture, salts and alkalis migrate upward slowly. This type of internal efflorescence cannot be eliminated simply by surface wiping. In severe cases, the plate must be returned to factory for re-lapping.
3. Light-shield storage to avoid UV-induced surface discoloration and aging
The storage zone must be kept away from light. Do not place plates under windows, skylights or long-term strong UV lighting. Ultraviolet rays in natural light continuously act on surface minerals of granite, destroy crystal bonding state and gradually cause gloss loss and local discoloration such as yellow and gray stains.
Light shielding is not limited only to the working surface. Sides and bottom of the slab also need light protection. Unilateral long-time illumination causes inconsistent aging rates on different parts of the stone and induces uneven micro-deformation. Use light-blocking soft dust covers during sealing. Transparent plastic films are not recommended, as they fail to block light and easily trap moisture inside and trigger efflorescence.
4. Pre-storage preparation: thorough cleaning and full drying to remove residual alkaline sources
Before warehousing and sealing, fully clean and dry the granite plate. Remove water stains, sweat marks, dust and residual alkaline cleaner from working surface, sides and bottom. If trace alkaline contaminants remain on the surface, efflorescence spots will form faster in humid storage environments.
After cleaning, do not seal immediately. Leave the plate to rest and fully dry in a space with stable temperature and humidity until all moisture inside stone micropores evaporates, then cover with light-blocking dust cover. Sealing while the slab still holds internal moisture traps water vapor inside the cover and salt frost easily precipitates on the surface. ZHHIMG® implements six-sided penetrating protection before delivery. The coating reduces water absorption but cannot completely block water vapor penetration under extreme humidity, so moisture protection during storage remains indispensable. 
5. Regular storage inspection and dynamic temperature & humidity monitoring
Do not leave sealed plates unattended for months. Record temperature and humidity during periodic inspections. Check whether condensation exists under dust covers and whether white salt bloom or discoloration appears at plate edges.
If excessive humidity is detected, activate dehumidification equipment promptly. If mild efflorescence is spotted, never scrub with strong acid or alkali. Transfer the plate to dry and ventilated space for slow air-drying and contact the manufacturer for professional treatment. Relocate plates temporarily if the storage area is renovated or wall leakage occurs.
6. Additional storage taboos to avoid combined factors triggering efflorescence and discoloration
Do not stack cement, quicklime, alkaline powder and similar materials inside the storage room. Alkaline aerosols released from these materials adhere to granite surfaces under high humidity and directly induce surface efflorescence after absorbing water vapor.
Dust covers need both light blocking and air permeability. Fully airtight plastic film shall not be used for long-term wrapping, as vapor easily condenses inside. Keep plates away from heat sources. Temperature differences accelerate vapor condensation on the surface. Maintain stable ventilation and avoid alternating hot and cold airflow to reduce repeated wet-dry cycles of the stone.
Conclusion
ZHHIMG® precision granite surface plates feature dense mineral structure and ultra-precision lapping for outstanding benchmark performance. Nevertheless, combined high humidity and illumination will gradually trigger hidden damage such as efflorescence and color spots during long-term storage. Moisture-proof and light-shield storage is not an optional extra protection measure, but the fundamental method to block salt migration and mineral aging. Stable humidity control, ground isolation by elevation, light-shield sealing, full drying before warehousing and regular temperature-humidity inspections effectively prevent plate efflorescence and discoloration, protect optical properties and flatness of nano-lapped working surfaces, extend metrological service life of the plate and cut re-lapping costs.
Post time: Oct-12-2026