Cob: linseed oil

[David Knowlton]

Matthew,

Excellent answer and excellent point sir. Sometimes 'natural' means 
"...nasty, brutish, and short."

David


>From: "Matthew HALL(SED)" <M.Hall at shu.ac.uk>
>Reply-To: "Matthew HALL(SED)" <M.Hall at shu.ac.uk>
>To: coblist at deatech.com
>Subject: Cob: linseed oil
>Date: Sat, 20 Apr 2002 20:52:23 +0100
>
>I recently refered to the use of linseed oil as a natural surface treatment 
>for earth walls and
>renders. Linseed Oil is obtained from linseed which grows on the flax plant 
>and can be obtained by
>various methods. The oil is refined to remove certain naturally-occuring 
>undesirable chemicals and
>sometimes further treatments are used such as earth bleaching (to give very 
>light drying oils). The
>natural odour of Linseed oil can also removed through a deodorization 
>process.
>
>There are 2 types of linseed oil available; raw and boiled. Raw Linseed Oil 
>is just that,
>completely untreated prior to packaging and contains no additives. Boiled 
>linseed oil has been
>altered through the addition of chemical drying accelerators, such as 
>certain solvents and drying
>agents. Boiled linseed oil is frequently mixed with 10-15% stand oil which 
>is a drying oil of
>increased viscosity, which is achieved through heating the oil in the 
>absence of oxygen. The word
>'solvent', in this context, is often wrongly associated with being 
>ecologically harmful but many
>common, natural materials are solvents and are very much needed for 
>everyday life such as water,
>alcohol:)
>
>In short, raw linseed oil is the pure extract from natural plant seed and 
>takes longer to dry than
>boiled linseed oil which includes drying agents but that aren't 
>necesserally non-organic or
>harmful.
>
>Regards
>Matthew
>
>
>
>____________________________________________________________________
>Matthew Hall BSc (Hons) GradBEng
>PhD Research Student
>Centre for the Built Environment
>Unit 9 Science Park
>Sheffield Hallam University
>Pond Street
>Sheffield S1 1WB
>England
>
>Tel: +44 (0) 114 225 3200
>Fax: +44 (0) 114 225 3206
>E-mail: M.Hall at shu.ac.uk
>
>
>
>
>


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