How to Make a Copygraph Pad.
—A copygraph pad, or hectograph, as it is often called—from the Greek hekaton which means 100, and graph to write, hence to write a hundred—is a gelatine pad for duplicating a letter or a drawing.
To use a copygraph pad you must write your original letter with an aniline ink; then you lay it on the pad and rub it down with your fingers. When you remove the sheet an impression will be left on the face of the pad and if now you lay a sheet of clean paper on the pad, rub it and pull it off you will have a copy almost as bright and clear as the original. In this way as many as 50 or 100 copies of the original letter can be made.
To make a copygraph pad put 1 ounce of the best gelatine in enough water to cover it and let it stand for 24 hours. Put a tablespoonful of table salt into a cup of water, pour it into the outside can of a water jacketed pot. Put 6 ounces of glycerine in the inside pot, set the pot on the stove and heat it good and hot, or to be exact, to about 200 degrees Fahrenheit.
Drain off all the water from the gelatine and put the latter in the glycerine while it is yet on the fire; stir the mixture slowly every once in a while in order to prevent bubbles from forming, and skim off the froth that forms on top of it. When you have a nice smooth mixture stir in a teaspoonful of oil of cloves to keep it sweet.
Next make a pan of sheet zinc a little larger than the letter you want to copy and ¹⁄₂ an inch high, or you can use a tin pie pan if you merely want to try it out. Set the pan on a level table, fill it with the hot mixture, let it stand over night and it is ready to use.
How to Copy a Letter.
—You must write your letter with a special aniline ink, called hectograph ink, and use a new steel pen to do it with.
While the writing is getting dry take a small clean sponge, wet it with cold water, squeeze it as dry as you can, wash the face of the gelatine with it before you try to make an impression or else you will spoil the pad.
This done, lay the sheet of paper with the written side down on the pad and gently rub your fingers over every part of it. Let the paper stay on the pad for a couple of minutes, then grip a corner of it and pull it slowly and evenly from the pad as shown in [Fig. 78]. Now you are ready to make your copies.