US2323469A - Manufacture of transparentized sheets for drawing, tracing, and copy reproduction - Google Patents

Description

Pmmea July 6, 1943 UNITED STATES MANUFACTURE OF 1 PATENT FF E TRANSPARENTIZED SHEETS FOR DRAWING, TRACING, AND COPY REPRODUCTION Y 7 Walker M. Hin'man; -Winnetka, and Walter G. 5

' Hollmann, Chicago, 111., assignors to The Frederick Post Company, Chicago, 111., 'a corpora-' tion of Illinois No Drawing. Application rulys, 1939, "Serial No.283,376

23 Claims. (cam-1 43 j v The present invention relate to tracing sheets as of cloth or paper, such as is used to receive ink, pencil or printing marks, or other images, commonly desired to provide a. light-transmitting figured sheet for use in reproducing copies 51 by a light-printing process.

Light-transmissibility'is a requirement. Tracing cloth is the more common article of this class.

starch or gelatin or like hydrophili substance, containing emulsified waxes or oils, or "other transparentizing agents, patticularly vegetable oils. It is actually translucent rather than transparent, although "transparency is referred toin relative terms, such as more transparent or less transparent instead of less translucent? and more translucent. This is because it is opaque to dis tant objects, and translucent to light, but transparent to images in surfacecontact withthe sheet. In discussing the-present invention the term transparent? will beused with the meaning above indicated.

A requirement of present day tracing cloth is 25 a matt drawing face to avoid gloss. Usually, the back has gloss to prevent accumulation of dirt. The face also must receive and hold ink or pencil or rinting. It must also withstand erasure. It

is desirable that, it be semi-waterproof to such extent that ink does not penetrate into the cloth, thus to permit erasing without destroying the cloth. and to such extent that moisture from the hands does not injure it.

These requirements of the face may be met by a special coating on the face. The coating may vary according to special uses. One coating may produc a good cloth for pencil and a poor cloth for ink, and another may produce a good cloth for ink and a poor cloth for pencil. Such coating treatments heretofore have lessened the transparency by r ason of the added coat. This is commonly effected by applying some sort of a lacquer. used. A grit or abrasive has also been included in such coating to give a good matt surface.- However, the addition of such grit takes away from the transparency and this limits the amount 'of grit which can be practically included.

We have observed that when an ordinary tracing cloth is coated with a lacquer without a grit, its transparency is reduced, and that the transparericy is further reduced in aging of the freshly lacquered cloth. We have studied this change,

have found the cause of it, and have supplied a remedy. We have also found that the remedy is useful in producing tracing sheets from other basic sheet materials, such as an ordinary sheet of paper, and that its use is not limited to opera- It is usually a fine grade of woven linen, or long staple cotton, or a mixture, filled with 10 in common parlance 15 A cellulose derivative base is commonly 45 tions on tracing cloth containing a transparentizingage'nt. It is an object of the present invention-to produce a transparenttracing sheet.

It is another object oftheinvention to convert sheet material such as cloth" or paper into a transparent sheet useful for tracings.

It-is a further objectoftheinvention tocoat,

an ordinary tracing cloth having a transparentize ing agent so as to improve its face without lessening the transparency of-the-clothitself, orwith improvement of the transparency of-the cloth itself. m

It is a still further object of the invention to coat an ordinary'tracing cloth with-a coating composition which provides a; coat. not perfectly transparent, and to obtain :a coatedproduct having a transparency greater. than the uncoated cloth. I 1

Another object of the invention is the provision of a coating on .tracing cloth which provides a matt face improved for both pencil and ink.-

- Another object of the invention i to a tracing cloth so transparentized-that the weave the following description and explanation of the 1 invention.

In experimenting with-various coatings on common tracing cloth, we have'discovered that applied solutions of coating ,material are ,ca-

pable of extracting transparentizing ;material from the body of the cloth into the coating. We have found-that the solvent in; the coating composition does this,.and further,;that, after the solvent has been evaporated, the migration of transparentizingagent ,from the cloth to the coating continues. The transparency of the body of the cloth isactually, lowered even though the coating itself be. perfectly transparent. However, where the coating has of necessity been'slightly translucent by reason of some inclusion therein, the transparency obtainedhas been reduced by two factors, namely the extraction of transparent-izing materialfrom the cloth, and the superimposition-of a light-obstructing coating. 'By means of the present inventionfwe may add'a light -obstructing coating with less orno loss, or even with improvement in the transparency of the cloth body itself;

We have been able to coat a tracing cloth with a light-obstructive coating and produce a coated clot-h more transparent than the uncoated cloth.

We accomplish our purpose in one way by using a coating solution which has its solvent power for the transparentizing agents of the cloth partially or wholly satisfied. We may produce transparency by using a coating solution which on drying yields a transparentizing. agent to the cloth. The process may be more mixed than above indicated. .For example, the coating solution or resulting film may extract some of the transparentizing agent from the cloth, and at the same time yield to the cloth the same or a different transparentizing material added to the coating for that purpose. Whether the final coated cloth, compared to the uncoated clot-h,

has more, or less, or the same transparency, depends entirely upon the manner in which the present invention is carried out. We prefer, obviously, tocarry out the invention to secure a coated cloth whichis more transparent after coating than before, and .hence illustrateour invention by a preferred procedure which accomplishessuch purpose.

However, it is to be understood that our invention is not limited to coating prepared tracing cloths on the market, which already contain a transparentizing agent. Our preferred procedure ofusing a, coating composition which readily yields a transparentizing agent, may be used to coat a paper or cloth, or other such sheet capable of being .transparentized, to yield said agent to the sheet coated, thus to transparentize it as well as coat it.

Thus, in either case, we obtain a tracing sheet which has a transparentized body and a transparentcoating, each containing a transparentizing agent for the body, whereby there is a balance of forces, one tending to cause migration of the agent from the body into the coat,' 'and the other'tending to cause migration of said agent from the coating into the body, or providing a partial or complete saturation of the film so as to prevent some migration from the body to the coat.

In the trade the tracing sheets provided (commonly of cloth) are primarily intendedto receive ink, but in those special cases where they have been specially treated to serve also in some acceptable degree for pencil, they, are termed pencilcloths.

Heretofore, pencil cloths have been of such grade as to limit their use to pencils of hardness H or 2K, in order to secure a satisfactory density to the line drawn. The inclusion of grit for tooth need not be limited by requirements for transparency.- Accordingto our invention, we may produce a coated cloth for pencil which is more transparent than the uncoated cloth, and which permits of sufiicientgrit so that it will take a pencil of 4H to 6H. Draftsmen prefer such harder pencils, because they make finer tions) of penciling a tracing and then inking over, or first penciling onto drawing paper, and then inking onto a tracing cloth placed over the penciled paper.

The trade prefers a tracing cloth rather than a tracing paper because the woven base gives strength and assurance against damage or tearfor such use, and as permanent records.

process and is carried on by but a few manufaclines, but heretofore they have not been able to use them because the line was not sufficiently turing sources. The resulting cloth has heretofore been employed for the receipt of a coating containing grit, to improve its surface, as described in British Patent No. 483,011 to Paul Koenig. In carrying out our invention we may begin with any original commercial "tracing cloths.!..,,We may also use our invention on any suitablefilledcloth even though lthas no transparentizing: agent in the filling. In such case, our process provides the transparentizing agent. For example we may use our invention on the following commercial tracing cloths which are already transparentized but not lacquered or otherwise coated over the filling material.

Imperial, Winterbottom Book Cloth Co., Ltd.,

Manchester, England.

Excelsior, Winterbottom Book Cloth Co., Ltd.,

Manchester, England.-

Arkwrightf' Arkwright Finishing Co., Providence,Rhod e Island.

Prudence, Arkwright Finishing Co., Providence, Rhode Island.

Kosmo Spezial, Richard Schwlkert. Freiburg, Breisgan, Germany. 1

.(No mark), J. Landauer, Braunschweig, Germany.

We may also use it on paper, a desired requirement of which is that it is not sized or filled with mineral filler which will add to opacity. Such paper may be absorptive of the coating composition canon-absorptive of it," so long as there is good adherence of the resulting film. Our preferred coating readily exudes the transparentizing agent into the paper, and apparently with considerable force Where there is a good interface by good anchorage.

In carrying out our invention in its preferred manner, 'we do not need to know the identity of the transparentizing. agents in a transparentized filled tracing cloth. In the trade, the basic item" sider the constituents of the cloth, but having" the knowledge that a transparentizing agent is extracted by a coating solution we'use a coating solution which has a transparentizing property for the filled cloth, in order to compensate for any detransparentizing effect, which the same composition might have. The latter effect may readily be determined by omitting the transparentizing agent which we add to our composition. We prefer to make the transparentizing effect greater than the detransparentizing effect, but this is not always necessary. Where we use but one coat, we must also consider the effect of the coating composition on the drawing surface, as well as upon the cloth.

We have found that by using a coating solution containing a transparentizing agent, the coating as applied, or as it dries, can share such agent with the cloth. The cloth also may share its transparentizing agent with the' coating.

Therefore, we prefer to use" enough agent to get a net improvement in transparency. However, we may use less than this amount and secure no change, or some loss in transparency, yet an improvement over use of a coating without a transparentizing agent to be shared by the cloth,

The character of the coating solution may vary widely, and commonly it embodies a solid base such as a cellulose derivative, bases, in a volatile solvent with plasticizer for giving flexibility. base requires a plasticizer therefor. We find that those plasticizers which are oily or liquid are also transparentizing agents. These may be synthetic, such as dibutylphthalate, or natural, such as caster or other vegetable oils and mineral oil. We may use a non-transparentizing agent as plasticizer, such as some of the alkyl sulfonamides,

and use a tran'sparentizing oil in addition, which,

may have some additional plasticizing. property. Plasticizers may be solvent plasticizer or non-solvent plasticizer. The former has a solvent power for the base plasticized, while the latter does not,

and is mechanically held or dissolved in the base plasticized. Castor oil and mineral oil are nonsolvent plasticizers for nitrocellulose, and if an excessive quantity is used as a plasticizer, the excess is rejected by exudation. It is this effect which is desired in this invention. Hence we use a transparentizing agent which isrejected, and its function as a plasticizer is only incidental. If the amount retained. is not sufficiently plasticizing we may add other plasticizer. This may or may not add to the transparentizing action. Where it is a solvent plasticizer it i less likely to exert a transparentizing action because the affinity for the base to hold it'is greater than the tendency to reject it and the tendency of the sheet to absorb makes the coating more thermoplastic, and subject to sticking to another surface, especially a like surface.

Where the transparentizing plasticizer is highly compatible with the base of the lacquer it is retained by the liquid lacquer and by the filmfrom the lacquer, and is not readily shared with the cloth, if at all, for the purpose of transparentizing it. For example, castor oil which is anon-solvent plasticizer for nitrocellulose, is normally a good transparentizing agent for the cloth, but it is too highly retained by the lacquer to be given up to the cloth. This is true of dibutyl phthalate and other solvent plasticizers. Hence, where we want the agent to be yielded to the cloth it must be one which in the quantity present, is not readily held by thefilm on drying or when dried. We therefore use a transparentizing agent which the film tends to reject, thus increasing the relative claim for it by the cloth. Because we use such a. rejectable agent for transparentizing, some of it may be left in the resulting coating as a plasticizer. This permits having solvent plasticizer,

it. Too much solvent plasticizer.

where it may be desired. However, by depending upon the retained agent as plasticizer and by not using solvent plasticizer," we produce a stickproof cloth. We prefer to use mineral oil as our transparentizing agent fora nitrocellulose base lacquer, because it has a limited solubility in a dried nitrocellulosecoating, and because it is or a mixture of For example a nitro-cellulose liquid, and readily exuded under normal conditions. Thereisa tendency for mineral oil dissolved'in common with nitrocellulose'in a solution to exude as the solvent'dries away.- This tendency to exude is augmented by contact with the tracing cloth to absorb it, thus transparentizing the cloth. The use of too much oil may of course cause some exudation at the drawing surface, which should not be undulyoily. The effect of this tendency will be discussed later.

v For the drawing surface for pencil, there must be a tooth. This is accomplished mechanically by including a gritor like substance. This is an additional inclusion in a lacquer coating which renders the coat less transparent than without it. It is an opaquing" agent, the effect of which reduces the benefits of including a transparentizing agent to benefit the body of the cloth or paper. secure greater transparency in the coated body sheet than in the uncoated sheet, in spite of the opaquing effect of the grit.

The gri may be any solid substance,-preferably a transparent mineral powder, and it may be chosen to have anxindex of refraction near that of the coating to render it less "opaquing." Because bonate, barytes and others. One reason for preferring silica is that it is' highly transmissive of ultraviolet light, which is a highly actinic component of the light rays used in reproducing copies such as blueprints and diazotypes.

We also prefer to coat but one side of the tracing cloth, or of paper. This has a real advantage in commercial handling of the material. As made, the coated material is rolled for storage, shipment and sale. This brings the coated'face against the uncoated face. The latter readily absorbs 'anyoil on the drawing surface present before rolling, or exuded while in the roll. Thus at the time of use, the surface is not oily.

We are not limited to coating but one face and may coat both faces. However, where we make such a change and use the same or similar solution on both sides, we reduce the amount of 'transparentizing agent in the composition by nearly one-half, because it enters the cloth from both sides. This reduces the amount present to 'be exuded at the surface, to such an extent that is an advantageous requirement because a coat- However, the invention may be used to I For example, we may tracing cloth as well as to the drawing face.

Although we have describedthe inventiongen erally and inits preferred aspect, as involving only one coating to provide a drawing surface, and to transparentize, or to prevent extraction or transparentizing agent where it ispresentit is to be understood that this does not limit the invention. The described applied coat maybe a first film or underfilm, on which another may be depo fdesired. The invention may be carried out; ytco'ating the glossy back of ordinary tracing cloth with a transparentizing. or a non-detransparentizing composition, without altering the drawing face of the cloth. Both surfaces may be coated to provide two drawing facesror the sheet. Numerous changes and modifications of the invention may be practiced.

use a coating according to thisinvention, but lacking grit, which will dry to a quite oily surface. Upon this we may apply another coating without any transparentizing agent, but carrying grit, to provide a nonolly drawing surface. r

Furthermore; "we may make a tracing sheet from paper byiapplying to a sheet of paper a lacquer composition, such as in Example 1, omitting the grit, to provide a glossy waterproof back and to transparentize the paper, and use the uncoated side of the paper for the drawing surface. Or this' drawingface may be coated with the same composition containingthe grit. Theuse of alarge amount ofabrasive gives excellence as a pencil cloth. This makes it unnecessary to press down onthe cloth to eflect a heavy line. Heretofore such pressing was necessary, and the physical depression made in the cloth showed up badly on-eraslng, and did not permit complete erasing. Heretoforeit has been practically impossible to use enough grit to give this property, because the quantity necessary would have detracted too much from transparency.. Because we are able to improve transparency, we may gofurther inthe direction of using more grit than the prior art would have permitted. The tracing cloth of this invention permits erasing with soft erasers such as art gum, and thus there is little if any removal of the coating substance below or laterally of the lines erased. r

vIn compounding the coating composition the components may be varied in .well known ways for the proper qualities. TI'he composition must exhibit good adherence to the cloth, and be tough enough to retain the grit well against erasures and drawing forces.-

The following compositions will illustrate the invention.

Exmm: 1 V Ground quartz (300 mesh) ounces 35 Anhydrous ethyl alcohol gallons 2 Stock solution A (see below)-- do 2 Pontacyl fast Blue R grams 0.4

Dissolved in anhydrous ethyl alcohol grams" 314 Neutral mineral oil (White Rose, Standard Oil of Indiana) cc 480 Stock solution A Anhydrous ethyl alcohol. gallons 20 5 to 6 second nitrocellulose pounds 8 Shellac (dewaxed) do 16 The silica which is preferably of size 300 mesh to start with, is first ground thoroughly in a ball 2,323,469 ing does not adhere to the glossy back of a basic mill for 12 hours to remove air,- to get the silica completely wet with the solvent, and to reduce the size of the quartz 'still further. Then the stock solution A is added, and the other in-.

gredients. The composition may be coated by a spreader, roll, orlike device onto the tracing cloth or paperand the solvent evaporated. The composition of the coating may be varied to get optimum results with any particular set of coating conditions or for different bases.

The foregoing example illustrates a lacquer having mineral .oil as a rejecta'ble transparentizlng agent. base of thelacquer is practically 2 parts of shellac and 1 part of nitrocellulose. Nearly one part of mineral oil (.85 part) is present.

alcohol base solvent. Such additional coatings have been used in practicing the invention.

There are other transparentizlng solutions that may be used in the present invention.

The use of the term mean that it must be tracing cloth" does not used for tracing. The

term is a sort of hang-over from the prior use of prior inferior products, which necessitated Tracing cloth heretofore was transparent for two reasons. The first one was to permit tracing the desired pattern or design onto the cloth. The second was to permit printing by light through the cloth. With the advent of the pres ent.ir1vention providing a transparent medium on which the lines required for printing may be made originally with pencil, it is now not neces- One reason for emphasizing opacity to reproduce like an ink line in lighton permits this drawing in pencil printing. The present inventi on paper or cloth, so that as a progresses, prints of that progress may be obtained prior to final inking, where that is desired. This has the particular advantage that a design in progress may be sent out to numerous individuals as blueprints or the like, thus eliminating the necessity for these individuals and the original draft to be assembled in one place.

Wherein we use the term tracing" for a sheet or cloth, we refer to a light-transmitting sheet wherein lines will appear so that the sheet may be used for reproducing said lines by use of light and light-sensitive sheets.

Wherein we refer to transparentizing agent for the sheet in the lacquer we do not necessarily mean that it is transferred to the sheet. Reference is made to the description above wherein the mere presence of it lessens the extraction of transparentizing from the sheet. The agent is thus transparentizing by indirection, but where it is usedon a sheet having no transparentizing agent before lacquering, it will become shared by the sheet and the coating.

The invention may be applied in many ways and is not limited to the specific illustration. Reference is made to our copending application, Serial No, 283,377, filed July 8, 1939, now Patent No. 2,253,562, issued August 26, 1941, wherein a more complex structure is formed, but in which the present invention is' embodied as expressed within the scope of the appended claims.

We claim:

1. A tracing sheet comprising in combination an original tracing cloth of the type which is filled with a hydrophilic colloid and transparentized with a permanent agent selected from the group consisting of oils, fats and waxes; a waterproof transparent lacquer coat on a face of said sheet, said original cloth and said coat both containing the same and a second permanent transparentizing agent selected from the group consisting of oils, fats and waxes, the coat being saturated with said second agent, whereby it cannot draw said second transparentizing agent from the clothto diminish the transparency of the filled cloth.

'2. A tracing sheet comprising in combination an original tracing cloth of the type which is filled with a hydrophilic colloid and transparentized with a permanent agent selected from the group consisting of oils, fats and waxes, a waterproof transparent lacquer coat having a nitrocellulose base on a face of said sheet, said original cloth and said coat both containing the same and a second permanent transparentizing agent selected from the group consisting of oils, fats and waxes, said coat being saturated with said second agent, whereby it cannot draw said second transparentizing agent from the cloth to diminish the transparency of the filled cloth.

3. A tracing sheet comprising in combination an original tracing cloth of the type which is filled with a hydrophilic colloid and transparentized with a permanent agent selected from the group consisting of oils, fats and waxes, a waterproof transparent lacquer coat having a nitrocellulose base on a face of said sheet, said original cloth and said coat both containing mineral oil as a second permanent transparentizing agent, the coat being saturated with said mineral oil, whereby it cannot draw mineral oil from the cloth to diminish the transparency of the filled cloth.

4. A tracing sheet comprising in combination an original tracing cloth of the type which is filled with a hydrophilic colloid and transparentized with a permanent agent selected irom the group consisting of oils, fats and waxes, a waterproof transparent lacquer coat having nitrocellulose and shellac bases on a face of said sheet, laid original cloth and said'coat both containing the same and a second permanent transparentizing agent selected from the group consisting of oils, fats ar-tl waxes, said coat being saturated with said second agent, whereby it cannot draw said second transparentizing agent from the cloth to diminish the transparency of the filled cloth.

5. A tracing sheet/comprising in combination an original tracing cloth of the type which is filled with a hydrophilic colloid and transparentized with a permanent agent selected from the group consisting of oils, fats and waxes, a waterproof transparent lacquer coat having nitrocellulose and shellac bases on a face of said sheet, said original cloth and said coat both containing mineral oilas a second permanent transparent izing agent, said coat being saturated with said oil, whereby it cannot draw mineral oil from the cloth. to, diminish "the transparency of the filled cloth.

6. A tracing sheet comprising in combination an original tracing cloth of the type which is filled with a hydrophilic colloid and transparentized with a permanent agent selectedirom the group consisting of oils, fats and'waxes, a waterproof transparent lacquer coat on a face of said sheet, said original cloth and said coat both containing the same and a second permanent transparentizing agent selected from the group consisting of oils, fats and waxes which second agent has limited miscibility with the material of said coat, the coat being saturated with said second agent, whereby it cannot draw said second agent from the cloth to diminish the transparency of the filled cloth, said coat also including a grit to provide a tooth for drawing at the surface thereof. I

7. A tracing sheet comprising in combination an original transparentizable fiber sheet, a waterproof transparent lacquer coat one. face of said sheet, said original sheet being transparentized by a permanent agent selected from the group consisting of oils, fats and waxes which agent has limited miscibility with the material of said coat, said coat being saturated with'the said agent, whereby it cannot draw said agent from the sheet to diminish the transparencyin aging.

8. A tracing sheet comprising in'combination an original transparentizable fiber sheet, a waterproof transparent nitrocellul'ose base lacquer coat on a face of said sheet, said original sheet being transparentized by a permanent agent selected from the group consisting of oils, fats and waxes which agent has limited miscibility with the said coat, the said coat being saturated with the said agent, whereby it cannot draw said agent from the sheet to diminish the transparency in aging.

9. A tracing sheet comprising in combination an original transparentizable fiber sheet, a waterproof transparent nitrocellulose base lacquer coatcoat, said coat being saturated with the mineral oil, whereby it cannot draw mineral oil from the sheet to diminish the transparency in aging.

10. A tracing sheet comprising in combination an original transparentizable fiber sheet, a waterproof transparent lacquer coat of nitrocellulose and shellac bases on a face of said sheet, said original sheet being transparentized by a permanent agent selected from the group consisting of oils, fats and waxes, said coat being saturated with such an agent, whereby said coat cannot draw transparentizing agent from the sheet to diminish the transparency in aging.

11. A tracing sheet comprising in combination an original transparentizable fiber sheet, a'waterproof transparent lacquer coat of nitrocellulose and shellac bases on a face of said sheet, said original sheet being transparentized by mineral oil, said coat being saturated with mineral oil, whereby it cannot draw mineral oil from the sheet to diminish the transparency in aging.

12. A tracing sheet comprising in combination an original transparentizable fiber sheet, a waterproof transparent lacquer coat containing grit for drawing tooth on a face of said sheet, said original sheet being transparentized by a permanent agent selected from the group consisting of oils, fats and waxes, which has limited miscibility with the material of said coat, said coat being saturated with such an agent, whereby it cannot draw transparentizing agent from' tlre sheet to diminish the transparency in aging.

13. The method of coating a. transparentized tracing sheet of fiber base which is filled with a hydrophilic colloid and which contains a permanent transparentizing agent selected from the group consisting of oils, fats and waxes, which comprises applying a waterproofing lacquer to a face of said sheet, said lacquer containing dissolved transparentizing agent for the said filled fiber-base sheet selected from the group consisting of oils, fats and waxes, said agent being present in quantity in excess of the capacity of the dried coat resulting from said lacquer to hold it dissolved therein, whereby it is in part rejected into the sheet in the formation of said coat, and evaporating the said lacquer to provide said coat.

14. The method of coating a transparentized tracing sheet of fiber base which is filled with 2.

- hydrophilic colloid and which contains a -perma-' nent transparentizing agent selected from the group consisting of oils, fats and waxes, which comprises applying a waterproofing lacquer having a nitrocellulose base .to a face of said sheet, said lacquer containing dissolved transparentizing agent for the said filled fiber-base sheet selected from the group consisting of oils, fats and waxes, said agent being present in quantity in excess of the capacity of the dried coat resulting from said lacquer to hold it dissolved therein, whereby it is in part rejected into the sheet in the formation of said coat, and evaporating the said lacquer to provide said coat.

15. The method of coating a transparentized tracing sheet of fiber base which is filled with a hydrophilic colloid and which contains a permanent transparentizing agent selected from the group consisting of oils, fats and waxes, which comprises applying a waterproofing lacquer having a nitrocellulose base to a face of said sheet, said lacquer containing dissolved mineral oil in quantity in excess of the capacity of the dried coat resulting from said lacquer to hold it dissolved therein, whereby it is in part rejected into the sheet in the formation of said coat, and evaporating the said lacquer to provide said coat.

16. The method of coating a transparentized tracing sheet of fiber base which is filled with a hydrophilic colloid and which contains a permanent transparentizing agent selected from the group consisting of oils, fats and waxes, which rejected into the sheet in the formation of said coat, and evaporating the said lacquer to provide said coat.

17. The method of coating a transparentized tracing sheet of fiber base which is filled with a hydrophilic colloid and which contains a permanent transparentizing agent selected from the group consisting of oils, fats and waxes, which comprises applying a waterproofing lacquer to a face of said sheet, said lacquer containing dissolved transparentizing agent for the said filled fiber-base sheet selected from the group consisting of oils, fats and waxes, said agent being present in quantity in excess of the capacity of the dried coat resulting from said lacquer to hold it, whereby it is in part rejected into the sheet and in part to the exposed surface of said coat in the formation of the coat, said lacquer also containing in suspension a finely divided grit to give tooth to said exposed surface for drawing thereon and in compensation for the greasy effect resulting from said rejection of said agent to the surface of the coat, and evaporating the said lacquer to provide said coat.

18. The method of making a transparentized tracing sheet of transparentizable fiber base which comprises applying to a face of said sheet a waterproofing lacquer containing transparentizing agent for said sheet selected from the group consisting of oils, fats and waxes, said agent being present in quantity in excess of the capacity of the dried coat resulting from said lacquer to hold it, whereby said agent is in part rejected into the sheet in the formation of the coat, said excess being sufiicient both to transparentize the sheet and to provide a coat containing said agent dissolved therein at least to the point r of saturation, and evaporating the said lacquer to provide said coat.

19. The method of making a transparentized tracing sheet of transparentizable fiber base which comprises applying to a face of said sheet a water-proofing lacquer having a base of nitrocellulose and containing transparentizing agent for said sheet 'selectedfrom the group consisting of oils, fats and waxes, said agent being present in quantity in excess of the capacity of the dried coat resulting from said lacquer to hold it, whereby said agent is in part rejected into the sheet in the formation of the coat, said excess being suificient both to transparentize the sheet and to provide a coat containing said agent dissolved therein at least to the point of saturation, and evaporating the said lacquer to provide said coat.

20. The method of making a transparentized tracing sheet of transparentizable fiber base which comprises applying to a face of said sheet a. waterproofing lacquer having a base of nitrocellulose and containing dissolved mineral oil in quantity in excess of the capacity of the coat resulting from said lacquer to hold it, whereby said mineral oil is rejected in part into said sheet in the formation of said coat, said excess being sufficient both to tra'nsparentize the said sheet and to provide a coat containing mineral oil dissolved therein at least to the point of saturation, and evaporating the said lacquer to provide said coat.

21. The method of making a transparentized tracing sheet of transparentizable fiber base which comprises applying to a face of said sheet a. waterproofing lacquer having bases of nitrocellulose and shellac and containing dissolved transparentizing agent for said sheet selected from the group consisting of oils, fats and waxes, said agent being present in quantity in excess of the capacity of the coat resulting from said lacquer to hold it, whereby said agent is in part rejected into said sheet in the formation of the coat, said excess being sufficient both to transparentize the sheet and to provide a coat containing said agent dissolved therein at least to the point of saturation, and evaporating said lacquer to provide said coat.

22. The method of making a transparentized tracing sheet of transparentizable flber base which comprises applying to a face of said sheet a waterproofing lacquer having bases of nitrocellulose and shellac and containing dissolved mineral oil in quantity in excess of the capacity of the coat resulting from said lacquer to hold it, whereby said mineral oil is rejected in part into said sheet in the formation of said coat, said excess being sufflcient both to transparentize the said sheet and to provide a coat containing mineral oil dissolved therein at least to the point of saturation, and evaporating the said lacquer to provide said coat.

23. The method of making a transparentized tracing sheet of transparentizable fiber base which comprises applying to a face of said sheet a waterproofing lacquer containing dissolved transparentizing agent for said sheet selected from the group consisting of oils, fats and waxes, said agent beingpresent in quantity in excess of the capacity of the dried coat resulting from said lacquer to hold it, whereby it is in part rejected from the two surfaces of said coat, part into the sheet and part to the exposed surface of the coat, said excess being sufficient both to transparentize the sheet to provide a, coat containing said agent dissolved therein to the point of saturation, and to provide a greasy exposed surface to the coat, said lacquer also containing a grit in suspension to provide tooth to the exposed surface of the coat for drawing thereon and in compensation for the said greasiness, and

evaporating said lacquer to provide said coat.

WALKER. M. HINMAN.

WALTER G. HOLLMANN.