28 1 



TINNING. 



Tinning is tlie art of covering any metal with a 

 tliin coating of tin. Copper and iron are the me- 

 tals most commonly tinned. The use of tinning 

 these metals is to prevent them from being cor- 

 roded by rust, as tin is not so easily acted upon by 

 the air or water as iron and copper are. 



What are commonly called tin-plates, or sheets, 

 so much used for utensils of various kinds, are in 

 fact iron-plates coated with tin. 



The principal circumstance in the art of tinning, 

 is to have tlie surfaces of the metal to be tinned 

 perfectly clean and free from rust, and also that 

 the melted tin be perfectly metallic, and not co- 

 vered with any ashes or calx of tin. 



Tinning of Iron. 



When iron-plates are to be tinned, they are first 

 scoured, and then put into what is called a pickle, 

 which is oil of vitriol diluted with water ; this dis- 

 solves the rust or oxyd that was left after scouring, 

 and renders the surface perfectly clean. They are 

 then again washed and scoured. They are now 

 dipped into a vessel full of melted tin, the surface 

 of which is covered with fat or oil, to defend it 

 from the action of the air. By this means, the iron 

 coming into contact with the melted tin in a 

 perfectly metallic state, it comes out completely 

 coated. 



When a small quantity of iron only is to be 

 tinned, it is heated, and the tin rubbed on with 

 a piece of cloth, or some tow, having first sprinkled 

 the iron with some powdered resin, the use of which 

 is to reduce the tin that may be oxydated. Any 



