SIST EN 16322:2014

Overview - EN 16322:2013 (Conservation of Cultural Heritage - Determination of Drying Properties)

EN 16322:2013 is a CEN test standard that specifies a reproducible method to determine the drying behaviour of porous inorganic materials used in or constituting cultural property. It applies to untreated, treated or aged materials (natural stone, mortar, plaster, brick, etc.) and defines how to record and interpret drying curves, drying rates and a drying index for comparative evaluation.

Key topics and technical requirements

• Scope and materials: Porous inorganic materials (sandstone, limestone, marble, mortar, plaster, bricks).
• Specimen preparation
  • Regular shapes (cubes, cylinders) with minimum dimension of 10 mm; at least 3 specimens per series.
  • Surface preparation (wet or dry polishing with P180 sandpaper), washing, and saturation by capillary rise (24 h) followed by immersion until constant mass (≤ 0.1% mass change over 24 h).
  • All faces except the defined drying face must be sealed (latex, foil) to force one‑sided drying.
• Test equipment and environment
  • Climatic chamber at 23 ± 1 °C and 50 ± 3 % RH; ventilated oven (60 ± 2 °C) and analytical balance (accuracy ≥ 0.01 g).
  • Chronometer, caliper (0.1 mm), desiccator and specified abrasives.
• Test procedure and weighing schedule
  • First weight is mmax (t = 0). To capture the first drying phase, take ≥5 measurements in the first hour, then hourly for 7 hours, then twice daily (≥6 h apart) until final mass is reached.
  • Maintain constant and reproducible air flow - ventilation strongly affects the first drying phase (Annex B).
• Data analysis
  • Compute residual water per area (Mi) and plot the drying curve (Mi vs time).
  • D1: drying rate for the first phase - slope from linear regression of initial aligned points (≥5).
  • D2: drying rate for the second phase - slope from linear regression of Mi vs sqrt(time) (≥5 points).
  • Knick‑point (tk): transition time between phases (select the larger intersection point).
  • Drying index (ID): area under the drying curve used for comparative purposes; depends on test duration and should be used only for like‑for‑like comparisons.
• Reporting: specimen dimensions, number, drying face area, raw weight data, plots (Mi vs time and vs sqrt(time)), D1, D2, tk, tf and ID (if used).

Applications and users

EN 16322:2013 is used by:

• Conservation scientists, heritage laboratories and conservation/restoration professionals assessing material hygric behaviour.
• Museum and site conservators evaluating effects of water, flooding, treatments (e.g., water repellents) or ageing on drying capacity.
• Materials researchers and contractors selecting compatible repair mortars or testing interventions to avoid prolonged moisture retention.

Practical uses include post‑flood condition assessment, comparative testing of surface treatments, material selection for repairs, and research into moisture transport mechanisms in heritage materials.

Related standards

• EN 15898 - Conservation of cultural property: main general terms and definitions (normative reference in EN 16322).
• CEN/TC 346 publications on conservation test methods (for wider context and complementary procedures).

Keywords: EN 16322:2013, drying properties, drying curve, drying rate, knick‑point, drying index, conservation of cultural heritage, porous inorganic materials, test methods.