Proceedings of tee Polytechnic Association. 697 



Mortar, which is composed of lime and sand is the best ground for 

 water-glass. The sands used must be free from salts, ground flints, 

 &c. The so called artificial sands are the. best ; they have an even 

 and sharp " corn." The lime may be slaked ; if fresh lime is used 

 it should be powdered fine to prevent "blowing ; " in both cases the 

 mortar should be rather poor in lime, Eoman cement, mixed with 

 mortar or with sand, also forms a good ground ; but plaster of paris 

 (gypsum) must be avoided in the last layer of mortar. 



The ground should be of an even grain, not smooth ; the larger 

 the wall and the details to be painted, the coarser the grain of the 

 sand may be. After the ground is perfectly dry, it ought to stand 

 for a week or two before painting is commenced. The colors used 

 for painting pictures, decorations-, or large surfaces are simply ground 

 fine in pure water ; the water is best purified by boiling. Tlie colors 

 are applied with water only. Those artists and decorators who are 

 used to paint in tempera, in body-colors or distemper, will find tliis 

 process easy ; those who are used to oil painting only require some 

 practice to master the details of manipulation. Before application of 

 color moisten the places with water, and should the gi'ound become 

 dry under the brnsh, it is kept moist with a syringe, throwing the 

 water in the form of a fine mist. In all cases where it becomes nec- 

 essary to paint over again, to deepen or highten the colors, the places 

 ought to be always moistened with a syringe. While painting is 

 going on the colors must not be touched or rubbed with the finger, as 

 they are now only "bound" with water, and are soon damaged and 

 rubbed ofi". When a picture' or a wall is finished the colors must be 

 " fixed,'' and now, for the first time, water-glass comes into operation. 

 For fixing the colors, the " fixing water-glass " is used. The surest 

 way of using it is to dilute the solution with pure water considerably. 

 That water-glass which is of the consistence of thick syrup may be 

 diluted with six times its bulk of water ; that which is sold as " fix- 

 ing solution " with an equal bulk of water. The whole surface is 

 evenly syringed over. Care must be taken not to apply too much, 

 or the colors may flow into each other. After the lapse of a day, the 

 water-glass having had time to combine and harden, a second coat is 

 applied ; this time the solution may be a little stronger. In most 

 cases the colors will all be " fixed " when the second " coat " is dry ; 

 if, however, some of the so-called meager colors, such as black, &c., 

 still rub ofiT with the finger, it is best to go over these with a soft 

 brush and water-glass. 



