100 LABORATORY EXERCISES 



Describe the appearance of the ends, faces, and edges of each 

 block or board. How do the two kinds of oak differ in appear- 

 ance? 



Try to drive a wire nail into each of the boards, about 1 cm. 

 (half an inch) from the end; which kinds split most easily? 

 Suggest why. 



b. Get a smooth piece of Georgia pine, or of yellow pine, that 

 has a knot passing through it. Describe the appearance of 

 the knot and of the wood around it. Wh,at is a knot? 



Paint one side of the board, both the knot and the wood 

 around it. Cover the knot on the other side of the board 

 with shellac; after a few minutes paint over both the knot and 

 the wood. Let the paint dry thoroughly for a day or two; 

 then examine the two sides of the board. What is the differ- 

 ence in their appearance? Is there any good reason why 

 knots in a board should be covered with shellac before 

 painting it? 



c. Put a piece of knotty yellow pine or hemlock in hot sun- 

 light or near a hot radiator or stove. What happens to the 

 knots? Describe the odor produced; what causes it? 



d. Make some brown stain by mixing ^ of a teaspoonful 

 of burnt umber with 2 teaspoonfuls of linseed oil, and then 

 adding about % of a cupful of turpentine. The materials 

 may be mixed in a "tin" can; the stain should be kept in a 

 stoppered bottle. 



Apply the stain with a cloth or brush to one face and the 

 smoothed end of each of your blocks of wood. Let the stain 

 remain on the wood for 5 minutes; then wipe it off with a cloth. 

 After the stain has entirely dried, examine the blocks. Which 

 were stained most deeply, the ends, or the faces, of the blocks? 

 Tell why. Which kind of wood "took" the stain best? Why? 



N. B. Be sure to burn the oily cloths, or to put them into 

 a covered metal can, so that they cannot set the building afire. 



