WOOD PRESERVATION Flashcards
- the process of preserving or increasing the life of wood either chemically or mechanically
WOOD PRESERVATION
OBJECTIVES OF WOOD PRESERVATION:
- increase durability and service life of wood
- increase natural resistance to decay
- stabilize the wood to environmental changes
- improve surface for mechanical wear
- chemicals applied to wood to make it more resistant to attacks of agencies of wood deterioration
WOOD PRESERVATIVES
REQUIREMENTS OF A GOOD WOOD PRESERVATIVES:
- permanent
- penetrative
- safe to handle and use
- harmless to wood and metal
- plentiful and available
- economical
TYPES OF WOOD PRESERVATIVE:
- Water-borne preservatives (WBP)
- Oil-borne preservatives (OBP)
– chemicals that dissolve in water
Water-borne preservatives (WBP)
Water-borne preservatives (WBP) :
a. Arsenic salts
b. Chromium salts
c. Copper sulfate
d. Borax and boron salts
e. Mercuric chloride
f. Copper chrome arsenate (CCA)
g. Boliden salts
h. Wolman salts
– include by-products of coal distillation, coal tar refining, petroleum refining and wood distillation
- A preservative treatment that is applied to wood in the form of solution in oil
Oil-borne preservatives (OBP)
METHODS OF WOOD PRESERVATIVE:
a. Brush and spray treatment
b. Dipping
c. Steeping
d. Soaking
e. Kyanizing
f. Hot and cold bath
– brushing or spraying preservatives over the surface of the wood to be treated
Brush and spray treatment
– immersing wood in a preservatives (WBP) for a few seconds or minutes
Dipping
– process of submerging wood in a tank of preservative in water solution
Steeping
– submerging wood on cold OBP for several days
Soaking
– steeping wood on mercuric chloride, patented by John Kyan in England in 1832
Kyanizing
– involves the immersion of seasoned wood in successive baths of hot and cold wood preservatives
Hot and cold bath
PRESSURE PROCESSES OF WOOD PRESERVATION:
- Full-cell process
- Empty-cell process
- High pressure sap displacement (HPSD)
- process used when maximum absorption of the preservative is desired
Full-cell process
Full-cell process:
Bethel process
- devised in the 19th century by the U.S. inventor John Bethell
- sealing the wood in a pressure chamber and applying a vacuum in order to remove air and moisture from the wood cells
Bethel process
- part of the preservative forced into the wood under pressure is subsequently recovered, so that the wood cells tends to be coated with preservative rather than filled with it
Empty-cell process
Empty-cell process:
a. Rueping method
b. Lowry method
- patented by Max Rueping of Germany in 1902
- it involves the application of preliminary air pressure to the wood cells tends to be coated with preservatives
Rueping method
- patented by C.B. Lowry in 1906
- an empty cell process in which the air in the wood is compressed solely by the preservative introduced into the cylinder under pressure
Lowry method
- introduced and patented by Dr. Auguste Boucherie (France, 1838)
- developed by the Forest Products Research Development Institute (FPRDI) in UPLB to be adopted for the use in rural areas
- a method where the sap from a freshly-felled log is forced out of the wood by a WBP solution introduced under pressure through a cylinder up fitted over one end of the log or pole
High pressure sap displacement (HPSD)
