Shellac Cement

Shellac is the basis of most adhesive cements. A good one is made by thickening shellac varnish (shellac dissolved in alcohol) with dry white lead, mixing the two with a putty knife on a piece of glass.

St. Johnsbury, Vt. W. H. Sargent.

A Cement For Mending Rubber Goods

Dissolve raw gum rubber or caoutchouc in bisulphide of carbon for a number of days in a tightly stopped bottle until it has the consistency of a thick paste. Make the surfaces to be cemented clean and dry before applying, and press joint tightly together. L. E. Muncy.

Syracuse, N. Y.

Cement Not Affected By Alcohol

Gold size is valuable as a cement for setting together parts of vessels containing alcohol as it is not affected by alcohol as are some other good cements. It has been used for setting the glass covers of circular levels, the glass afterward being burred over in the brass shell so that it is securely held mechanically. Ordinary painters' size is used, which may be prepared as follows: Boil raw oil in a pan until it smokes, then set it on fire and let burn for a few moments. Cover the pan to extinguish the blaze and pour while warm into a receptacle containing red lead and litharge in the proportion of one ounce of each to a quart of oil. Keep at a temperature of 70 degrees for ten days and agitate once a day. M. E. Canek.

Acid-Proof Cement

Mix a concentrated solution of soda with pulverized glass to form a paste.

Birmingham, Eng. W. R. Bowers.

Glycerine-Litharge Cement

A handy cement to have in the shop for stopping leaks, etc., and which can be used for cementing glass, brass, etc., is made by mixing equal parts of litharge, commercial glycerine and Portland cement. This cement will harden under water and will withstand hydrocarbon vapors.

Dayton, Ohio. O. E. Voris.

Portland-Tar Cement

A valuable cement used in marine practice and other places where elasticity is desirable, is made by mixing Portland cement in gas tar until the consistency is that of stiff putty. It must be applied immediately as it quickly hardens. It is not affected by water and never becomes brittle, a fact that makes it very valuable around the tail-shafts of steamers or wherever there is much vibration. A. L. Graffam.

Hampton, Va.

Waterproof Cements

To make a good waterproof cement in a thin paste form, dissolve 1 ounce powdered resin in 10 ounces strong ammonia and add 5 parts gelatine and 1 part solution of acid chromate of lime. For waterproof cement in paste form, add to hot starch paste one-half its weight of turpentine and a small piece of alum. T. E. O'Donnell. Urbana, Ill.

Cement For Arc Lamp Carbons

The short ends of old arc lamp carbons may be cemented together to form rods which burn quite well, and are no more brittle than ordinary carbons. The cement required is made by mixing potassium silicate and carbon dust to a consistency of a thick paste. The ends of the short carbon pieces are faced off square, and, after application of the paste, are pressed together by hand. 0. G.

Waterproof Cements For Glass

Probably the simplest and best aquarium cement (the formula for which is recommended by the United States Fish Commission) is made as follows: Stir together by weight 8 parts pulverized putty (dry whiting), 1 part red lead and 1 part litharge. Mix as wanted for use with pure raw linseed oil to a consistency of stiff putty. Allow it to dry a week before using.

Another waterproof cement is made by dry mixing 10 parts each by measure of fine dry white sand plaster of paris and litharge and 1 part powdered resin. Mix as required to a stiff putty with boiled linseed oil. The linseed oil must be free from any trace of adulteration with fish oil. It is sometimes necessary to boil pure raw linseed oil a few moments to drive off the water. A. L. Graffam.

Indiana, Pa.