Wattle & Daub: Craft, Conservation & Wiltshire Case Study
Contents 2 History
3 Craft
3.3 Panel Types
3.4 Staves
3.6 Daub
3.7 Decoration
4.1 Soils
4.1.1 Constituents
4.1.2 Plasticity
4.1.3 Strength
4.1.4 Field Testing
4.1.5 Selection
4.2 Dung
4.2.2 Lignin
4.2.3 Urine
4.2.4 Microbial Debris
4.2.5 The Role of Dung
4.3 Fibre
5.2.3 Maintenance
5.3 Repair
5.3.1 Partial Renewal
5.4 Replacement
5.4.1 Brick Infill
5.4.2 Renewal
6.3 Fieldwork
6.5 Evaluation
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4.2.2 LigninThe modern study of lignins has identified many useful
properties and they are increasingly being used in modern manufacturing. Two of
the uses are as a binder and a dispersant. One such use of lignin’s
binding properties includes the stabilisation of soils. Dispersants attach
themselves to particle surfaces and so prevent the particles from being
attracted to each other. As a result, a dry mix requires less water than would
otherwise be needed to make the material workable. For example, lignin may be
used in cement mixes as a
dispersant.[65]
The fraction of lignin in cow faeces is dependent on the feed. Historically, the predominant fodder was pasture and hay, which recently has been estimated to have a lignin content of approximately 2 to 8%. Legume fodder often has a higher lignin content of up to approximately 12%. The lignin is almost wholly indigestible and so is passed directly into the faeces.[66] In considering the analysis of dung and the qualitative evaluation of the effects of lignin on daub, it must be realised that modern cattle feeds are often different to those used historically. Where cattle graze on pasture, the modern perennial ryegrass has been bred from improved strains developed by the Ministry of Agriculture Fisheries and Foods during the 1950’s.[67] As fast growing species, these are likely to have less lignin that historical ryegrass. The desire to maximise digestible content of cattle feeds has also led to the reduction in the fraction of indigestible cellulose and lignin. The Acid Detergent Fibre (ADF) laboratory test represents a measure of the non-digestible feed and comprises some of the cellulose and nearly all of the lignin from the food. Since ADF figures are readily available and ADF has a reasonable correlation to lignin content, these data may therefore be used to identify possible trends in lignin content. Table 2 shows how modern feeds have a lower ADF content than traditional feeds. Table
2. Comparison of acid detergent fibre in traditional
and modern cattle feeds. Adapted from Stanton (2004).
Therefore, in the evaluation of advantages of adding dung to daub, this downward trend of lignin content should be considered: if lignin led to the benefits observed by historic daubers then the same effect may not be reproducible using dung resulting from modern feeds. [65]
Lignin Institute (1992).
[66]
Van Soest (1982), pp.43-44.
[67]
Farm Direct (2001).
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