To Make Cloth Waterproof

There have been various devices for rendering cloth waterproof without the use of India rubber. The most successful of these, no doubt, is the Stenhouse patent. This consists of the application of paraffine combined with drying oil. Paraffine was first used alone, but it was found to harden and break off from the cloth after a time. When drying oil was added, however, even in a very small quantity, it was found that the two substances, by the absorption of oxygen, became converted into a tenacious substance very like resin. To apply this the paraffine is melted with drying oil and then cast into blocks. The composition can then be applied to fabrics by rubbing them over with a block of it, either cold or gently warmed. Or the melted mixture may be applied with a brush and the cloth then passed through hot rollers in order to cover its entire substance perfectly. This application makes cloth very repellant to water, though still pervious to air.

Preserving Wood

There have been a number of processes pat-ended for preserving wood. One of them, very generally used, consists in immersing the timber in a bath of corrosive sublimate. Another process consists in first filling the pores with a solution of chloride of calcium under pressure, and next forcing in a solution of sulphate of iron, by which an insoluble sulphate of lime is formed in the body of the wood, which is thus rendered nearly as hard as stone. Wood prepared in this way is now very largely used for railroad ties. Another process consists in impregnating the wood with a solution of chloride of zinc. Yet another way is to thoroughly impregnate the timber with oil of tar containing creosote and a crude solution of acetate of iron. The process consists in putting the wood in a cylindrical vessel, connected with a powerful air pump. The air is withdrawn, and the liquid subjected to pressure, so that as much of it as possible is forced into the pores of the wood. The processes above given not only season the timber, so that it t is not subject to dry rot, but also keep it from being injured by the weather, or being attacked by insects or worms.

To Transfer Engravings

It is said that engravings may be transferred on to white paper as follows: Place the engraving a few seconds over the vapor of iodine. Dip a slip of white paper into a weak solution of starch, and when dry, into a weak solution of oil of vitriol. When again dry, lay the slip upon the engraving and place both for a few minutes under a press. The engraving will be reproduced in all its delicacy and finish. Lithographs and printed matter cannot be so trans-ferred with equal success.

Luminous Paint

This useful paint may, it is said, be made by the following simple method: Take oyster shells and clean them with warm water; put them into the fire for half an hour; at the end of that time take them out and let them cool. When quite cool pound them fine and take away any gray parts, as they are of no use. Put the powder in a crucible in alternate layers with flour and sulphur. Put on the lid and cement with sand made into a stiff paste with beer. When dry, put over the fire and bake for an hour. Wait until quite cold before opening the lid. The product ought to be white. You must separate all gray parts, as they are not luminous. Make a sifter in the following manner: Take a pot, put a piece of very fine muslin very loosely across it, tie around with a string, put the powder into the top, and rake about until only the coarse powder remains; open the pot and you will find a very small pow-der; mix it into a thin paint with gum water, as two thin applications are better than one thick one.

This will give a paint that will remain luminous far into the night, provided it is exposed to light during the day.

Making Blackboards

The following directions for this work are given by an experienced superintendent: The first care must be to make the wall surface or boards to be blacked perfectly smooth. Fill all the holes and cracks with plaster of Paris mixed with water; mix but little at a time; press in and smooth down with a case-knife. The cracks between shrunken boards may be filled in the same way. Afterward use sandpaper. The ingredients needed for slating are (1) liquid gum shellac, sometimes called shellac varnish; (2) lampblack or drop black. Gum shellac is cut in alcohol, and the liquid can be obtained of any druggist. Pour some shellac into an open dish, and stir in lampblack to make a heavy paint. With a clean brush, spread on any kind of surface but glass. Put on a little and test it. If it is glossy and the chalk slips over it, reduce the mixture with alcohol. Alcohol can be bought of any druggist. If it rubs off, let the druggist put in more gum to make the liquid thicker. One quart of the liquid and a five cent paper of lampblack are sufficient to slate all the blackboards in any country school with two coats.