Forestry 280 - Chapter 8: Wood and Water Overview: Location of Water in Wood Moisture Content Forestry 280 - Chapter 8: Wood and Water

Forestry 280 - Chapter 8: Wood and Water Importance: Utilization problems Water effect on properties - Strength - Dimensions - Heating Value - Electrical - Acoustical - Insulation - Decay Resistance Forestry 280 - Chapter 8: Wood and Water

Forestry 280 - Chapter 8: Wood and Water Water in Woody Cells Water Interacts with Woody Cells on Two Levels: Fiber Level – Water can reside in the cell lumen. - Contain: sugars, inorganic components (sap) - Free Water Molecular Level Hydrogen bonds to hydroxyl (OH) groups Cellulose, Hemicellulose, Lignin? OH groups called sorption sites Bound Water Forestry 280 - Chapter 8: Wood and Water

Forestry 280 - Chapter 8: Wood and Water Water in Woody Cells Forestry 280 - Chapter 8: Wood and Water

Forestry 280 - Chapter 8: Wood and Water Water in Woody Cells Forestry 280 - Chapter 8: Wood and Water

Forestry 280 - Chapter 8: Wood and Water Water in Woody Cells Clarification: Adsorb versus Absorb Wood can aBsorb water like a sponge - Capillary effects (surface tension) - Free Water Wood can also aDsorb water - Intermolecular hydrogen bonds - Reversible phenomenon - Cause of wood hygroscopic character Forestry 280 - Chapter 8: Wood and Water

Forestry 280 - Chapter 8: Wood and Water Water in Woody Cells Equilibrium Moisture content (EMC) – MC at which wood has no net gain or loss of moisture when surrounded by air at a given relative humidity and temperature. Moisture In = Moisture Out Forestry 280 - Chapter 8: Wood and Water

Moisture Content (MC): a measure of the amount of water in wood MC = [ Weight of Wood plus Water – Oven Dry Weight of Wood ] X 100 Oven Dry Weight of Wood = [ Weight of Water ] X 100 OD Weight Since MC calculation is based on OD weight, it can have values greater than 100% Forestry 280 - Chapter 8: Wood and Water

Forestry 280 - Chapter 8: Wood and Water Moisture Content Typically the weight of wood plus water is referred to as “Green Weight” (GW) Therefore: MC% = [ (GW – OD) / OD ] X 100 Several Definitions of green weight: Weight of felled tree Weight of wood above fiber saturation point (FSP) Weight of wood at any MC above zero Forestry 280 - Chapter 8: Wood and Water

Forestry 280 - Chapter 8: Wood and Water Moisture Content Determination Measurement of MC: Typically accomplished by oven dry method: American Society for Testing and Materials (ASTM) Standard D 2016 Gravimetric determination: Weigh / Heat / Weigh Electronic moisture meters use electrical properties to estimate MC Forestry 280 - Chapter 8: Wood and Water

Forestry 280 - Chapter 8: Wood and Water Moisture Content Determination Dry in oven @ 103 ± 2oC 24 Hours Weigh Wet Sample Weigh Oven Dry Sample Calculate MC per equation For samples greater than 1 inch thick, the drying time should be extended until sample weight is constant. Forestry 280 - Chapter 8: Wood and Water

Forestry 280 - Chapter 8: Wood and Water Moisture Content Determination Oven Dry Method: Advantages – Simplicity Relative Accuracy Disadvantages – Destructive Duration Volatile wood components Forestry 280 - Chapter 8: Wood and Water

Forestry 280 - Chapter 8: Wood and Water