Chalk surface coated

Areas of application include wood coloration [45], paper mass coloration [46] and paper surface coating in the lime press [47], the office articles and artists colors sector pigments are used in colored pencils, crayons, and writing and pastel chalks or in water colors, as well as in cosmetics, especially soap [48],... 

Fading. This can be caused by poor light-fastness of the pigments used, or by chalking. The use of the cheaper, low-fastness red, and yellow organic pigments can represent a serious problem in exterior quality surface coatings. 

For the less critical applications, standard (epichlorhydrin/bisphenol A) epoxy resins retain their physical properties well, but are particularly subject to the adverse effects of UV radiation on their appearance. This causes rapid yellowing and chalking due to their aromatic structure and UV agents are ineffective. Therefore, aU mouldings made with these resins which are to be subjected to extended outdoor exposure will benefit from protection by surface coating or shading. 

Surface conditioner n. Preparatory coating applied to a chalked surface to bind chalk to the substrate, prior to top coating. 

Surface layers may be calcium carbonate, hydroxide or, in freshly broken crystals, possibly calcium oxide. It is now well established that coccoliths in chalk are coated with very thin aluminosilicates (smectites and other clay minerals) and organic matter (humates, etc) [6]. During comminution, compaction or metamorphosis, these coatings may be disrupted or may still adhere to the calcite surface. Aluminium silicates have been identified in pure limestones and pure marbles, and have been shown to be unattached to calcite fragments. 

The normal visible deterioration of a paint coating is by the appearance of chalking on its surface. Chalking is the term used to denote the powdery material that appears as the binder slowly disintegrates and exposes the pigments. 

These materials are now widely used for coating both steel and concrete surfaces that are subject to a particularly aggressive environment (e.g. North Sea oil platforms). There is less validity for their use under normal atmospheric conditions since they are relatively expensive and tend to chalk on exposure to sunlight. However, their use as zinc phosphate, pretreatment or blast primers for blast-cleaned steel which is subsequently overcoated by any other paint system is an extremely valuable contribution to the painting of new steel work. 

Chalking Formation of powdeiy layer on surface of coating that is being eroded away... 

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