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Color response in silver birch during kiln-drying
Member, Forest Products Society.
2004 (English)In: Forest products journal, ISSN 0015-7473, Vol. 54, no 6, 31-36 p.Article in journal (Refereed) Published
Abstract [en]

Color change in silver birch caused by kiln-drying is a major down-grading factor and has substantial economical impact on high value furniture and flooring production. This study investigates the color responses to process parameters at different stages in the drying process. Samples were dried in a climate chamber and laboratory kilns and the color of dry wood was registered according to the CIE L*C*h color system. The results show that during the capillary drying phase (moisture content > 55 %) time is more important than temperature. Swift initial drying even at elevated temperatures increases the lightness and decreases the saturation. The major color changes occur later on, during the diffusive drying phase from approximately 30 to 20 percent moisture content. Here a combination of temperature, time, and initial moisture content is decisive for the final wood color. Swift drying in both stages even at moderately elevated temperatures results in a highly desirable brighter color.

Place, publisher, year, edition, pages
Forest Products Society, 2004. Vol. 54, no 6, 31-36 p.
National Category
Other Materials Engineering
Research subject
Technology (byts ev till Engineering), Forestry and Wood Technology
Identifiers
URN: urn:nbn:se:lnu:diva-29006OAI: oai:DiVA.org:lnu-29006DiVA: diva2:650919
Available from: 2013-09-24 Created: 2013-09-24 Last updated: 2017-12-06Bibliographically 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. 78 p.
Series
Linnaeus University Dissertations, 148/2013
Keyword
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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