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Colour response of Silver birch to press drying
Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
2003 (English)In: Proceedings of the 8th International IUFRO Wood DryingConference, 2003, p. 449-454Conference paper, Published paper (Refereed)
Abstract [en]

Press drying is a rapid drying technique capable of reducing deformation, but also known to cause discolourationin some wood species. The colour of Silver birch is of great importance to the furniture and flooring industry, wherethe blond colour is highly appreciated. This study investigates the colour response in the core of 36 mm Silver birchsamples to the process variables: plate temperature, plate pressure and air pressure and to the material variable initialmoisture content. Short samples were press dried in a electrically heated laboratory press to approximately 10%moisture content and the interior colour of dry wood was registered according to the CIE L*C*h colour system. Theresults show that plate temperature is the most influential process variable controlling the wood colour. Hightemperature results in brighter more yellowish colour and reduced drying time. Other process and material variablesalso have some influence on the final colour but their contributions are smaller. Press drying of green wood at 170Cin normal atmospheric air pressure gave a wood colour comparable to that of conventionally kiln dried birch wood,only slightly darker and more reddish. The study indicates that press drying of Silver birch is possible from a colourperspective by careful selection of process parameters.

Place, publisher, year, edition, pages
2003. p. 449-454
National Category
Other Materials Engineering
Research subject
Technology (byts ev till Engineering), Forestry and Wood Technology
Identifiers
URN: urn:nbn:se:lnu:diva-29004OAI: oai:DiVA.org:lnu-29004DiVA, id: diva2:650916
Conference
8th International IUFRO Wood Drying Conference, Brasov, Romania, August 24–29
Available from: 2013-09-24 Created: 2013-09-24 Last updated: 2013-10-08Bibliographically approved
In thesis
1. Colour Response in Drying of Nordic Hardwoods
Open this publication in new window or tab >>Colour Response in Drying of Nordic Hardwoods
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Colour and appearance of hardwood are of great importance for the interiorand furniture industry. The widespread use of transparent surface treatmentand a fashion that prescribe light colour on many species, means that deviationfrom the ideal have considerable impact on the industrial operations. Kilndrying is generally regarded as the process that has the greatest impact on thecolour of Nordic hardwood species. The lack of satisfactory explanation modelsfor many types of discoloration, however, complicates the control of the dryingprocess.This thesis is an attempt to increase the knowledge of which factors thatcontrol the appearance of some commonly found discolorations associated withdrying of beech, birch and oak. The main focus is on convection drying but alsothe influence of timber storage, pre-steaming and press drying has beeninvestigated for individual species. The studies have been conducted ascomparative studies based on design of experiments in which the colour wasdetermined using a colorimeter.Results show that reddish and dark discoloration of beech and birch duringconvective drying is mainly dependent on the temperature and time of exposurewhen the local moisture content exceeds the fibre saturation point. Theconversion of naturally occurring substances in birch into coloured compoundsis not due to active precursors created at high moisture content levels duringthe subsequent drying at low moisture content levels. Interior grey stain inbeech is caused by slow initial drying at low temperatures. Log storage in coldwinter and spring climate does not cause discoloration in beech. Birch becomeslighter when press-dried at high temperatures, resulting in a colour comparableto that of traditionally kiln dried wood. Steaming of oak before kiln dryingreduce the presence of brown discoloration, a general darkening of the woodoccurs at temperatures above 50°C.

Place, publisher, year, edition, pages
Växjö: Linnaeus University Press, 2013. p. 78
Series
Linnaeus University Dissertations ; 148/2013
Keywords
beech, Betula pendula, birch, CIELAB, discolouration, drying, Fagus sylvatica, log storage, oak, press drying, wood colour, Quercus robur
National Category
Other Materials Engineering
Research subject
Technology (byts ev till Engineering), Forestry and Wood Technology
Identifiers
urn:nbn:se:lnu:diva-29011 (URN)978-91-87427-52-7 (ISBN)
Public defence
2013-10-18, M1088, Linnéuniversitetet, Växjö, 10:00 (English)
Opponent
Supervisors
Available from: 2013-10-08 Created: 2013-09-24 Last updated: 2016-08-22Bibliographically approved

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Stenudd, Stefan

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