102 farmers' and mechanics' journal. 



When a bright polish is not desired, but the work is to appear 

 with a fine surface, the grain may he laid with the glass-paper and 

 oil ; with oil and fine powdered pumice-stone, or with the finest 

 washed emery and oil, upon a buff. 



Burnishing on brass, is performed only on inferior kinds of work, 

 or upon such parts as do not admit of being polished. A burnish- 

 ed surface is the most brilliant, but has much less truth than one 

 which is well polished. For brass, steel burnishers are always 

 used. (The general directions in the article on burnishing, ex- 

 tracted from the Dictionnaire Technologique, and published in our 

 present number, may be referred to, upon this subject.) In bur- 

 nishing small articles, the burnisher may be moistened by touching 

 it with the tongue : weak beer is frequently used for larger work, 

 instead of the soap-suds, used with silver, as mentioned in the pa- 

 per just referred to. After burnishing, the articles are washed 

 clean, and wiped perfectly dry, when they are fit for lackering. 



On Finishing Wrought work. 



Wrought work, after having the parts which are intended to be 

 burnished, either scraped or filed, is to be annealed in a charcoal 

 fire ; a pickle is then made, by pouring aqua fortis {nitrous acid) 

 into water, until it is inteiisely sour ; into this pickle the articles 

 are put, and suffered to remain until all the black scale is removed 

 and the whole surface exhibits one clear, uniform red ; they are 

 then to be taken out, washed and dried, when they are ready for 

 dipping, or taking ojf. Some clear aqua fortis is poured into a cup, 

 and the article, if small, is dipped into it, and immediately remov- 

 ed ; otherwise it is washed over by means of a piece of rag, tied 

 on .v5 the end of a stick ; the acid immediately boils up, when it 

 must be washed ofT, by being passed successively into two or three 

 vessels containing water, as the smallest portion of acid will cause 

 the surface to tarnish. A little practice will enable the operator 

 to judge of the instant when the acid should be washed ofT, by the 

 color which it assumes. The surface will now exhibit a clear and 

 beautiful gold yellow, provided the brass and the acid are both of 

 a proper quality. The parts which are to be burnished, undergo 

 that operation, either by hand or in the lathe, according to the na- 

 ture of the articles. The usual mode is to put them into small 

 beer, from which fhe pieces are successively taken and burnished, 

 when they are thrown into clean water, and dried in the saw-du«t 

 of some wood which is not resinous. Sometimes the work is 

 scratch-brushed, before burnishing ; this, however, removes that 

 beautiful dead appearance, which is in general preferred, and 

 leaves a general brightness upon the uiiburnished parts. 



The scratch-brush is made of small brass wire, formed into bunch- 

 es, which for large work are fixed around a chuck, and made to re- 

 volve in the lathe ; beer is used in this operation, as in burnishing, 



[Am. Mcch. Mag. 



