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Wood Shrinkage

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Fibre Saturation Point In Wood

Water is present in wood in 2 forms. These forms are bound water and free water. Water which is absorbed by the wood and held within the cells is called bound water. Any water that is in excess of the fibre saturation point is called free water.

Fibre saturation point (FSP) is the moisture content of wood where the cell walls of the wood are completely saturated with bound water, but the cavities of the cells are devoid of any free water. This fibre saturation point is usually expressed numerically of moisture content in wood. The numerical range is usually between 25 - 30%.

Sap within living trees is mostly water with just a few small amounts of dissolved nutrients and minerals. Wood within a living tree is always in a condition above the fibre saturation point even though the moisture content level in that wood can vary.

When the tree is harvested and then the wood seasoned for use all the free water and some of the bound water is dried away. Bound water is never lost until all the free water is taken away.

 

 

Wood moisture meter

Concrete moisture meter

When working with wood an understanding of the reason it shrinks, moves and the direction the shrinkage is likely to take is essential. One has to bear in mind as well that in these modern times there is an increased usage of artificial heating which contributes to drier atmospheres and increased shrinkage within wood. It doesnt matter on the age of the wood as all wood is affected. It is not the heating which is the problem, but the drier air which is created by the heating.

When you think of wood shrinkage and the direction it takes, you should visualize a tree as a compact cylinder which has many smaller cylinders inside it. When a tree does dry out shrinkage will occur in every direction except for the length. The circumference of the tree will shrink and all the inner cylinders will shrink and tighten up, becoming more tightly packed.

Shrikage factors along the length of wood can be ignored in most case as the shrinkage is only fractional. You need to concentrate on tangential and radial shrinkages where the shrinkage can be substantial. A huge problem here is that the most shrinkage in wood takes place between critical moisture content of dried wood and fully conditioned wood. Just looking for oak as an example can highlight this issue. When oak is dried down from a 20% moisture content level to 12% content level it will shrink by approximately 2.5%. A low number you may think but a substantial change in size!

All woods shrink when dried which causes internal strains and stresses. The results can be artificial defects to the wood. Usually a wood structure has natural elasticity and any stresses are distributed evenly. But if the wood structure lacks elasticity or incorrect seasoning is employed, the wood will distort in various forms.

 

Cupping - Here a rounding on the underface takes place.

 

Bowing - The wood curves and takes on the shape of a bow.

 

Springing - Also known as edge bend. The wood here stays flat but bends edgewise.

 

Twisting - Here the long egdes are straight and the diagonals are curved.

 

Splitting - wood will begin to split if subjected to rapid drying.

 

Flaking - The surface of the wood lifts in many small flakes creating a rough surface.

 

Case hardening - If wood is dried too quickly in a kiln then the surfaces will dry out quicker than the body and create a hard casing with a soft inner.

 

Honeycombing - If you dry case hardened wood in a kiln then the interior will dry out but any moisture will be locked in the outer case causing a honeycomb effect.

 

 

 

Moisture Meter Guide 2010                                                                                               Contact details:garnett65@hotmail.com

The complete moisture meter website

Moisture Meter Guide

 

 

Wagner Moisture Meters

Wagner MMC220

Wagner MMI1100

Wagner MMC210

Wagner MMC205

Wagner L606

Wagner L607

Wagner C575

Wagner BI2200

Delmhorst Moisture Meter

Delmhorst BD-10 Pin

Delmhorst J-2000

Delmhorst J-Lite

Delmhorst P-2000

Delmhorst BD-2100

Delmhorst J-4

Delmhorst Accuscan

Delmhorst KS-D1

Delmhorst Dual Function

Tramex Moisture Meters

Tramex Encounter Plus

Tramex Compact Wood

Tramex Concrete Encounter

Tramex Skipper Plus

Tramex Roof And Wall

General Tools Moisture Meter

General Tools MMD4E Digital

General Tools MM1E Pin LED

General Tools MMD950

General Tools MMD5NP Pinless LCD  

General Tools MMH800 4 In 1

General Tools GLMM200 Soil

General Tools MMD7003 Precision  

General Tools MMD8P Multi Species

General Tools MMD7NP LCD

General Tools MM700D Precision

Sonin Moisture Meters

Sonin 50218 Digital

Sonin 50270 Digital

Sonin 50210 Test Tool

Sonin 50211 Test

Extech Moisture Meter

Extech MO280 Pinless

Extech MO230 Pocket

Extech MO257 Pinless

Extech MO260 Combi

Extech MO260 Pin/Pinless

Extech MO270 Wireless

Extech MO210 Pocket

Extech MO210 Pocket

Extech MO220 Wood

Extech 407777 Heavy Duty

Lignomat Moisture Meter

Lignomat Mini Ligno E/D

Lignomat Mini Ligno S/D

Lignomat LED Wood

Lignomat Mini Ligno E

Lignomat Mini Ligno DX/C

Lignomat Scanner D

Lignomat Ligno Duotec

Lignomat Mini Ligno S

Protimeter Moisture Meter

Protimeter Mini

Protimeter Aquant

Protimeter Surveymaster

Protimeter Hygromaster

Protimeter Psyclone

Protimeter Timbermaster

Protimeter MMS

Protimeter MMS2

 

 

 

 

 

 

 

 

 

 

 

 

Boat Moisture Meter

 

 

 

 

 

 

 

A moisture meter proves itself to be a useful tool when testing the moisture content levels of boat materials. When assessing a boat, care, judgement and experience should all be employed and then the moisture meter used as the last tool to give the final assessment. Damp tester for boats

 

 

Need A Chainsaw For Firewood?

 

 

 

 

The petrol chainsaw is used to fell trees, as well as for pruning and cutting overgrowth. Tree surgeons favour the petrol chainsaw and use it for cutting away branches and foliage. Chainsaw information

 

Orchid Moisture Meter

 

 

 

 

 

The orchid belongs to a widespread and very diverse family of flowering plants which have fragrant and colourful blooms. Orchids can be found in pretty much every habitat. Moisture meter for orchids

 

 

Caravan Moisture Meter

 

 

 

 

 

Any caravan that is kept open to the elements all year round can become very susceptible to damp and damp related problems if proper precautions are not taken to prevent this. Caravan meter

 

 

Garden Moisture Meter

 

 

 

 

 

 

 

 

 

 

The garden moisture meter helps any avid gardener to measure and monitor many different conditions to ensure that they can maintain healthy growing conditions for both indoor as well as outdoor plants. In order to have healthy thriving plants Garden and soil meter

 

Which Is The Best Firewood?

It is a good and important question to ask. There are differences between how different types of firewoods burn. Suitable firewood

 

Floorboard Advice

 

 

 

 

 

 

 

 

 

 

 

 

Wooden floorboards must be acclimatized >

Prevent and repair gaps in wooden floorboards >

How to fix a squeaky hardwood floor >

How to repair a buckled hardwood floor >