| 摘要 |
<p>Method of colouring metal articles comprises first preparing the articles by cleaning thoroughly with a (pumice) abrasive, degreasing with caustic potash, and deoxidn. in an appropriate acid esp. dil H2SO4. The metal is then treated in specific locations to attack by lead acetate to produce localised iridescence. The article is then dipped in a bath of hot metallic salts suitable for producing the desired colour. Aqs. Bi2(SO4)3 and potassium tartrate soln. produce a brownish colour after 3 mins or violet after 15 mins. CdSO4 + potassium tartrate produces a reddish colour after 3 mins and grey after 15 mins. and (PbSO4 or SnSO4) + sodium hyposulphite produces a bluish colour after 2 mins and grey after 15 mins passing through violet as intermediate colour. The article is then washed and dried in sawdust or similar absorbent material. A preservative varnish of clear nitrocellulose is finally applied.</p> |
