| 摘要 |
<p>The surface of the material is treated with a soln. which precipitates amorphous or crystalline solids in the network of fissures or microfissures in the material, so the latter changes colour. The soln. pref. contains ions reacting with the metals in at least one of the constituents in the material so metal ions are pptd. in the fissures. Metals may be added to the initial soln. to produce the desired colour in the material, which is esp. grey granite given a brown colour via an alkaline oxidising soln. with min. pH 7-8, esp. a soln. contg. lime, soda, or ammonium salts. The pref. oxidising solns. contain Na2S2O8; NaOCl; KClO4; or NaHSO4. The esp. pref. soln. parts consists of 50-100 g Na2S2O8 and 5-10 g Na2CO3 in 100 cm3 of water, to which 0.25-1 g Fe powder is added. Used esp. to ppte. goethite in the fissures in felspar, and in the junctions between quartz and felspar, in grey granite to produce a brown colour; or for colouring other stones or concrete.</p> |
