146 Laboratory Arts 



"finishing" being a process possible only by so long a 

 practice as to be almost beyond our attainment. 



Each coat of polish should be put on more lightly than 

 the last, less pressure and less polish being necessary as 

 the true surface is obtained. 



Finishing is a somewhat tedious process. It consists in 

 using more and more dilute solution at each successive stage, 

 drying and glass-papering in between each as may be 

 necessary, for French polish should never be a veneer, merely 

 at most a surface, until finally pure spirit (spt. vini. rect.) 

 alone is used on the rubber. In the hands of the beginner 

 this invariably results in the complete destruction of his 

 previous work, but this is usually caused through using too 

 moist a pad the pad for these last stages being almost 

 dry, save for a little oil. 



Where cheapness and extreme gloss are essential,, various 

 substances such as gum benzoin are used towards the 

 end of the process, but though these produce a wonderful 

 surface at the time, it is somewhat soft, and the gloss fades, 

 leaving a polish inferior to that obtained by the first process 

 alone. 



Polish applied according to the above instructions upon 

 oak, walnut, ash or other hard wood will be as good in twenty 

 years as at first, but it will not be as bright as that secured 

 by a professional polisher though probably less fleeting. 



Great care should be taken to include the edges of any 

 surface being polished, in order to spread out evenly any 

 of the solution that may be squeezed over the side. Should 

 this happen and pass unnoticed, nothing short of entire 

 removal by glass-paper can remedy the fault. 



XV. GRADUATION AND CALIBRATION OF APPARATUS. 



The calibration of apparatus is usually undertaken after it 

 has been graduated, as many operations are more easily accom- 

 plished then ; but it is easily seen that the calibration should 

 come first, save that this would entail a large amount of extra 

 trouble. Glass apparatus is rarely constant in volume, it alters 



