US2004484A - Stencil sheet and method of making the same - Google Patents

Description

Patented June 11, 1935 STENCIL SHEET AND METHOD OF MAKING THE SAME Louis G. Brandt, Portsmouth, Va.,, assignor to The Multistamp Company, Inc., Norfolk, Va., a corporation of Virginia No Drawing. Application May 3, 1932, Serial No. 609,046. Renewed November 15, 1934 9 Claims. (01. 41-53815) This invention relates to stencil sheets, which, as is Well known, are universallymade from sheets of Yoshino paper coated with a composition which is type-impressible, so that the sheet may be put in a typewriter and after receiving the impression of the type, may be removed and placed over an inked pad, the ink from which seeps through the narrow apertures cut in the coating composition by the type and thus reproduces, on a sheet of paper, the message typed out. Such sheets have been in use for perhaps fifty years, and many different compositions have been proposed and used with more or less success. The least expensive stencil sheets, today as for the past forty or fifty years, are coated by a composition made largely from paraffin, but as they will yield only about 50 or '75 copies, wax stencils are little used. Stencils made of protein (gelatin) were extensively used ten to fifteen years ago,but as such sheets hadto be moistened, and moisture was injurious to typewriters, besides causing a loss of time, they were never considered wholly satisfactory. The introduction of a nitrocellulose stencil, about 1925, caused practically a discontinuance of protein or wet stencils; and today probably of all stencil sheets used in this country are of a nitrocellulosic composition, usually softened with vegetable or mineral oils or fatty acids, such as stearic acid.

There are two very serious drawbacks to nitrocellulose stencils: first, that they deteriorate, slowly but surely, althoughvery rapidly if exposed to a little heat; second, that they are expensive.

A sheet 18" x 25" may cost, in wholesale lots, about nine cents, to which must be added various manufacturing costs, overhead, packing and shipping expense, sales expense, allowances for spoilage, returns, etc. The result is that the retail price for stencil sheets is too high for many people to bear. School teachers, for example,

have need, many times a day, of a stencil sheet, so thatevery member of each class may be given instructions, quizzes, etc.; but because of the high cost of stencil sheets of the better class, and the highly unsatisfactory nature of the poorer grades of stencil sheets, the use of stencil duplicators has never attained anything like the proportions which it should in American schools. It is not too much to say that there is an imperative demand for an extremely cheap stencil sheet which will be capable of making hundreds, or even thousands, of clear copies. The present invention makes possible the production of such a stencil sheet. 7

In accordance with the invention, and as one illustrative exampleof the manner in which. the invention may be practiced, I take 13 gm. of protein (gelatin) and add 10 oz. of clean water, heating to 212 F. The gelatin, of course, dissolves, to make solution No. 1. Then I take 1.5 oz. of pure soap of almost any composition (one example being Ivory soap) and 10 oz. of clean water, boiling to make solution No. 2. Then I compound the two solutions at 212 F., and add 3 gm. of any water soluble dye of the desired color. The inexpensive'dyes which are used to color Eastereggs are entirely suitable, I have found.

Stirring is continued for some time to insure complete dissolving and. uniform mixing of the dye. Cooling is thenpermitted, to about 150 F., when I add, to the above-described mixture, 1 oz. of almond oil and 1 oz. of pure glycerin (or I may use 2 oz. of almond oil instead) and mix thoroughly. When the mixture has cooled to -90 F., it may be applied to a sheet of Yoshino paper in any suitable way, and the coated sheet should then be hung up to dry at ordinary room temperatures. After drying is sufliciently complete, I dip the coated sheet in a 15% solution of formaldehyde, thus coagulating the gelatin to make it waterresistant, and then hang up the sheet again to dry at room temperatures. The sheet is now ready for packaging or storing. g

Stencil sheets made as described will cost only about one cent per 18 x 25" sheet, or only oneninth of the cost of nitrocellulose sheets of a quality scarcely superior. Experiments show that upwards of 4000 legible copies may be made from a single stencil sheet. Thus the two desiderata mentioned above are fully realized by the invention.

However, the invention has other important aspects. First, the stencil sheets are substantialchanges: an important improvement when it is recalled that the cheap wax stencils and the expensive nitrocellulose stencils'are both ruined by a little heat, such as will be found near a radiator. Secondly, the sheets will Stand considerable handling, without injury, whereas wax stencils will not. Thirdly, there is no deterioration: thec'omposition used is inert and is non-hygroscopic, non-hardening, non-softening. Fourthly, the raw materials used are all readily available almost anywhere, in unlimited quantities, at low prices. Fifthly, the sheets withstand packing, pressure, rolling, storage, shipping and other commercial treatment, without injury to themselves or to anything with which they come in contact, either before or during use. Thus the importance of the advance I have made in the art will be apparent.

Obviously, the invention may have various embodiments, provided they are within the scope of the appended claims. For example, I may use many oils and oil compounds in place of the almond oil mentioned above.

Having described a preferred embodiment of the invention and the best manner now known to me of practicing the invention, what I claim as new and desire to secure by Letters Patent of the United States of America is:-

1. A stencil sheet comprising a sheet of Yoshino paper coated with a composition comprising coagulated, water-resistant gelatin, soap and an oil, present in the following approximate proportions by weight: 13:42 56, respectively.

2. A stencil sheet consisting of a sheet of Y0- shino paper coated with a composition made from the following ingredients: 13 gm. of coagulated water-resistant gelatin, 1.5 oz. of pure soap, and 2 oz. of an oily tempering agent.

3. A stencil sheet consisting of a sheet of Y0? shino paper. coated with a composition made from the following ingredients: 13 gm. of coagulated, water-resistant gelatin, 1.5 oz. of pure soap, and .302. of almond oil.

4. A stencil sheet consisting of a sheet of Y0- shino paper coated with a composition compris ing :13 gm. of coagulated, water-resistant gelatin, 1.5 02.01 pure soap, 3 gm. of water-soluble dye, 2 oz. of oil.

5. A stencil sheet consisting of a sheet of Y0- shino paper coated with a composition comprising 13 grrnof coagulated, water-resistant gelatin, 1.5 oz. of pure soap, 3 gm. of water-soluble dye, 1 oz. of oil and 1 oz. of glycerin.

6. That method of making a composition for coating stencil sheets which comprises preparing an aqueous solution of gelatin, preparing an aqueous soap solution, compounding the two solutions; and finally adding an oily tempering agent in sufficient quantity to at least equal the amount of soap and gelatin present in the solution.

'7. That method of making a composition for coating stencil sheets which comprises the making of a protein solution from 13 gm. of gelatin and oz. of water; heating said solution to 212 F.; making a soap solution from 1.5 oz. of soap and 10 oz. of water and heating the soap solution to 212 F.; compounding the two solutions; allowing the mixture to cool somewhat and adding a quantity of oil about equal to the amount of dry soap and gelatin present in the solution and finally cooiing to below 100 F.

8. A stencil sheet comprising a sheet of Y0- shino paper coated with a composition comprising coagulated, water-resistantgelatin, soap and an oil; theproportion by weight of soap being over three times that of the gelatin, and the proportion by weight of oil materially exceeding that of the soap.

9. A stencil sheet comprising a sheet of Yoshino coated with a composition comprisin coagulated, water-resistant gelatin, soap and amixture of an oil and glycerin in substantially equal parts; proportion by weight of the soap being over three times that of the gelatin, and

L. G. BRANDT.