Cellulose products

There are two different cellulose paints; one based on cellulose paste, the other on nitrocellulose. The latter is used mainly for varnish and must contain up to 75% organic solvents and softeners. The cellulose paste paint has approximately the same properties as collagen glue paint.

Cellulose paints are mainly based on renewable resources from plants. The products are made from methyl cellulose in a highly polluting process. The production and use of organic solvents in products of nitrocellulose are damaging both to nature and to the painter.

Within buildings these products are not a problem. Painted material can probably be burned in normal incinerators or dumped on domestic tips without any problem, with the possible exception of varnishes of nitrocellulose when hazardous substances have been added.

18.5 STAINS

Stains are used on wood and do not contain added binders. There are two main types of stain: chemical stain and water stain.

Chemical stain is based on a colour reaction with substances in the timber. Tannic acid can be used, as can green vitriol. Lye treatment is based on sodium hydroxide (NaOH) often with lime or titanium white added (Figure 18.3). In commercial products small additions of vegetable oil, from soybeans or coconut, can be found. Interior surfaces exposed to heavy wear should have an extra treatment of green soap or vegetable oil to facilitate cleaning.

Water stain is made with pigments that are soluble in water. Modern exterior stains usually also contain metal salts such as cobalt chloride,

18.3

Wooden surfaces treated with lime lye. Gaia Lista, 2008.

18.3

Wooden surfaces treated with lime lye. Gaia Lista, 2008.

copper chloride, potassium dichromate, manganese chloride and nickel chloride, in order to impregnate the wood. Several ordinary pigments can be used in the stain; but even bark or onion peelings are used as stain colours.

Stains are fully open to vapour and therefore the full potential for moisture buffering in the underlayer can be utilized. Stains are also the least resource demanding treatments and they are relatively problem free in both production and use. Exceptions are water stains with metal salts added. These are usually toxic and can seep into the soil. The same can be said for the waste from these stains and they require special waste treatment. As far as the other products are concerned, re-use, recycling, composting and dumping are all relatively problem free. It is only the addition of poisonous pigments that reduce the quality of an otherwise very positive environmental profile.

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