Impregnation all the way to the core
Preservation through pressure impregnation means that wood preservatives containing active substances against rot, fungi and insects are pressed into the tree. Impregnation ensures deep and full penetration into the sapwood, and the result is better protection against biodegradation than for example the natural protection and durability of the pine heartwood.
The lightest part of the wood, the sapwood, is saturated with impregnating liquid and is protected against biological organisms. Heartwood is not normally penetrated through impregnation as the structure and density of the heartwood and the content of resin and heartwood substances do not allow penetration of the impregnating agents.
Pressure impregnation is done in closed tank systems. Before impregnating the wood, it is verified that the wood is healthy (free of fungi and microorganisms). Similarly, the wood must be free of bark, dried and processed into the requested profile.
The wood is placed in the tank, and vacuum is used to extract moisture and air. The tank is then filled with impregnating liquid, and the active substances are pressed into the wood under pressure. Once the process is complete, the pressure tank opens, and excess liquid drips off. All liquid is collected and recycled. Before the wood can be delivered to the customer, the wood must be fixed for 48 hours so that it does not drip any more.
The Danish Environmental Protection Agency requires that Danish pressure-impregnated wood must be fixed before delivery and that the tree is placed with joists in between. There are no requirements for imported wood. In principle, it can be delivered un-fixed, wet and without joists which may involve an occupational health risk.
External quality control
Frøslev only uses water-proofing agents for which a risk assessment has been carried out and which have been approved by the Danish Environmental Protection Agency. This provides a guarantee for durability as well as environment. Danish Impregnation Control, an external quality control, and our internal control guarantee the quality of our process and products.
The quality of impregnated wood is evident if the liquid has penetrated all the way to the heartwood. If the wood has only been immersed in impregnation liquid, the liquid will only have penetrated a few mm into the wood. To ensure good quality, make sure that the wood is produced in Denmark and has been impregnated according to the NTR standards. Then the quality is in order.