Scientijfic Intelligence. 207 



It is universally known, lliat the acids, either single or combined, 

 in different degrees, are the agents, employed in producing these 

 beautiful efi'ects upon tinned iron. 



The following mixtures may be employed with perfect success, 

 upon tin plate gently heated. 



1. Four parts of nitric acid, one of muriate of soda or of muriate 

 of ammonia, two of distilled water. 



2. Two parts of nitric acid, one of muriatic acid, and from two to 

 four parts of distilled water. 



3. One part of nitric acid, two of muriatic acid, three of distilled 

 water. 



4. Two parts of nitric acid, two of muriatic acid, two of distilled 

 water, and two of sulphuric acid. 



Process. — Either of the above mixtures being placed in a common 

 glass, a sponge is wet with the fluid, and immediately applied to the 

 tin plate, until it is every where equally moistened. If the plate has 

 been slightly heated, or the acid has been but little diluted, the pecul- 

 iar configuration, [moire,) is produced in less than a minute, other- 

 wise it will require from five to ten minutes. Afterwards the plate 

 is wet with cold water, and washed by rubbing it gently with a piece of 

 cotton, or with the plume of a quill, but by no means with the hand ; 

 it is then left to dry. It is never proper to pour the acid upon the 

 plate, because this will produce great black spots where it falls ; fre- 

 quently one part will be oxidized before the other parts are sufficiently 

 crystallized, because the acid is not every where equally diffused at the 

 same moment. Oxidation takes place also, if the plate after washing*^ 

 be dried too near the fire, and, as the same effect will happen from 

 the gradual action of the air, it is necessary to varnish the work.* 



What is called le moire force, is produced by bringing the tin plate 

 into contact with red hot iron, and then applying the acids to the op- 

 posite side. Stars and other very beautiful designs are made by 

 bringing into contact with the tin plate, the flame of an enameller's 

 lamp, but with so much caution as to be sure that the tin is not melted. 



Although these operations appear to be easy, it is impossible to 

 succeed well without acquiring a certain tact by practice. 



The washing is the most important thing. An instant, more or less, 

 alters the effect entirely. If the process be stopped too soon, there 

 is no beauty or lustre, if not soon enough, the plate becomes dull and 



* By employing colored and transparent varnisbes, the beauty of the work ia 

 greatly increased, — Ed. 



