182 Chemical Aids to Art. 



When they have been dried, they require heating over a lamp, 

 to a heat below redness. For this purpose they may be sus- 

 pended, by means of a fine wire, over a spirit or an oil lamp, 

 in such a way as not to touch the flame. Suddenly, before 

 they have had time to cool, the objects are to be completely 

 plunged beneath the surface of the platinizing liquid. One 

 immersion for a single minute generally suffices; but the 

 process may be repeated if necessary, care being taken to 

 wash and dry the pieces operated upon before re-heating them. 

 The composition of the solution may vary considerably, and 

 yet good results be obtained. Sometimes the addition of 

 more honey improves it; sometimes the proportion of bi- 

 chloride of platinum may be increased or diminished with 

 advantage. Indeed, it will be found that the appearance of 

 the platinum film deposited upon the objects may be altered 

 by changing the proportion of the bichloride present. The 

 solution may be used several times ; gradually, however, it 

 loses all its platinum, the place of this element being taken by 

 the iron or copper dissolved off the immersed objects. 



We may now appropriately mention a few examples where 

 this platinizing process seems to furnish desirable results. 

 Articles made of iron or steel — watch-chains, seals, sword- 

 handles, keys, and similar useful or ornamental objects — are 

 greatly improved in appearance, and, moreover, preserved 

 from all chance of rusting, by this treatment. The colour of 

 the platinum film is of a neutral greyish black, and it often 

 shows at the same time a faint iridescence. Iron or steel which 

 has been inlaid with gold or silver, forming what. is known as 

 damascened work, is greatly improved by platinizing. Neither 

 the gold nor the silver are in the least degree affected, and 

 they will be found to afford a better contrast with the colour 

 of the platinized than with that of the original iron.* Other 

 artistic applications of this process will readily suggest them- 

 selves : coins, medals, chains, and ornaments of brass and 

 copper may be instanced as excellent subjects for experiment. 

 If they have been partially gilt or silvered before treatment 

 with the platinizing liquid, those parts only of the specimen 

 which show the original metal will change in colour. In this 

 way very beautiful and effective designs of gold on platinum, 



* Iron which lias become deeply rusted cannot be platinized, by our process. 

 In order, however, to preserve from further destruction objects of steel »or iron 

 having an archaeological or artistic interest, a very excellent plan may be used as 

 a substitute. The purest white paraffine is to be melted in a clean pan, and 

 maintained at about the temperature of boiling water. The rusted and corroded 

 specimens are to be immersed in this -paraffine bath till they cease to froth from 

 escape of moisture. They are then withdrawn, wrapped in blotting pap r, and 

 kept in a warm place till the excess of paraffine has been absorbed. The objects 

 thus treated, while preserved from further decay, do not acquire that disagreeable 

 greasy aspect which the varnish ordinarily used imparts. 



