460 Popular Science Monthly 



A Book Shelf and Trough Made of A Good Elastic Varnish for Coating 



Soft Wood 



THE illustration shows the construction 

 of a simple book shelf and trough com- 

 bined. The sides are made of 1-in. yellow 

 pine boards that taper in width from 14 in. 

 at the bottom to 

 11 in. at the top. 

 The strip at the 

 top extends over 

 the edges of the 

 upright boards 1 

 in., and the base 

 strip extends out 

 2 in. The shelves 

 are fitted into 

 grooves K i^^- 

 deep. In the 

 place of one shelf, 

 a trough is set in 

 which holds the 

 books in an up- 

 right position. 

 The shelves are 

 convenient for 

 large volumes. 

 Besides gluing 

 all parts together, 



Dimensions of the parts that enter into the construc- 

 tion of a simple combination book shelf and trough 



round head screws are 

 used to strengthen the joints, and to im- 

 prove the appearance. The completed book 

 shelf can be finished with two coats of stain 

 and one of either varnish or wax. For small 

 jobs like this, it is best to procure finishing 

 material in small cans from your dealer. 

 Follow directions on the containers as differ- 

 ent makers recommend different use of 

 such products. — H. Alden. 



Glass Cements for Commercial 

 or Domestic Use 



WHEN finely pulverized chalk is stirred 

 into a solution of water glass at 

 30°B. until the resultant mixture becomes 

 fine and plastic, a cement of extraordinary 

 durability is obtained. It will harden in 

 about seven hours. The cement, when mixed 

 with a little zinc dust, will adhere to almost 

 any surface. After burnishing, such a ce- 

 ment will exhibit the white and brilliant 

 appearance of metallic zinc. A small quan- 

 tity of carbonate of copper added to the 

 chalk will produce a bright green cement. 

 Cobalt blue wil give it a .splendid blue 

 coloration, vermilion a bright red, and car- 

 bon red will produce a violet color. 



Blue Prints 



THE greatest drawback to the use of 

 drawings or blue prints in machine 

 shops and factories, is that they soil so 

 quickly owing to handling. This obscures 



the dimensions of 

 the various ma- 

 chine sizes, mak- 

 ing their reading 

 slower, and al- 

 lowing possibili- 

 ties for mistakes. 

 In order to keep 

 blue prints clean 

 and make them 

 last longer, one 

 chief draftsman 

 coats them with 

 a flexible and wa- 

 terproof varnish. 

 This enables the 

 drawings, or blue 

 prints, to be wiped 

 off with a wet 

 cloth when they 

 become soiled. It 

 taken into damp 



also allows them to be 

 places. 



The formula for the varnish is as follows: 

 Crush transparent and clear pieces of gum 

 damar into small grains, then place a con- 

 venient quantity — say forty grains— in a 

 flask. Pour on it about 6 oz. of acetone and 

 expose the whole to a moderate temperature 

 for about two weeks, or until the mixture 

 has dissolved. It is necessary to shake the 

 flask frequently. 



At the end of this time, pour off the clear 

 saturated solution of damar in acetone, and 

 add to every four parts of the varnish, three 

 parts of rather dense collodion, mixing the 

 two solutions by shaking. The resulting 

 fluid is allowed to settle and it can be pre- 

 served in well closed phials. 



This varnish is applied in vertical lines by 

 means of a soft camel's hair brush. At the 

 first application it will appear as if the sur- 

 face of the paper were covered with a thin 

 white skin. As soon, however, as the var- 

 nish dries, it presents a clear shining surface. 

 The varnish should be applied in three 

 layers, or coats. It will be found by ex- 

 perience, that this varnish retains its gloss 

 and remains pliable under all weather con- 

 ditions.— W. S. Standiford. 



