Starch paint is based on starch glue made from rye or wheat (pages 379-380) and is mainly used externally on planed timber. The paste decays over time and only pigment is left. This can rub off. To compensate, it is common to add about 5-7% linseed oil in an emulsion. For use in damp environments 1-2% green vitriol can be added to prevent mould attack.
Starch paint has high vapour permeability. It does not flake or peel and is easy to apply and maintain. It is resistant to fungal attack. Tests have shown it to have better durability than other commercial paints (Hansson, 1999). In Scandinavia, starch paint has a long tradition of being commonly tinted with red or yellow ochre pigments.
Starch paint is based on renewable raw materials from plants and represents no environmental threat, either in its production or use. Reuse and recycling of treated materials is acceptable, as is burning for energy recovery. The materials can normally be composted. However, the favourable environmental profile can be reduced by the addition of environmentally damaging pigments.
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