Document RJ9novMGnzY2R7dpnJ31EbBMB

FILE NAME: CertainTeed (CERT) DATE: 1954 June 22 DOC#: CERT064 DOCUM ENT DESCRIPTION: US Patent L 'J 06-99 Patented June 22, 1954 p c c r n - " ' ' rr\_ r . u. : ~V A Sr ! ! / UNITED STATES PATENT OFFICE' /fA 2,681,883 PLASTER COMPOSITIONS AND PRODUCTS Michele ^Croce and Clarence G. Shuttleworth. Evanston, III., a ssIg m < n C ta d ^ P ro " i S * * Ardmore>T C acorporatim i No Drawing. Application In ly 7,1981. Serial No. 235,688 9 Claims. (CL 108--109) This invention relates to plaster compositions ndto products made from such compositions. Thus, in the use of plaster compositions such as those heretofore employed, the workability of where plaster compositions have been utilized to the past to produce either plastered walls, the set plaster composition has in many instances been adversely influenced by the presence of the Plaster wallboard, or plaster casts of various rands, the resulting casts have in most instances sisal fiber, sawdust or like fillers that have been used, and it is an Import rmt object of the present been relatively hard to handle and use because invention to enable the physical characteristics of the relatively frangible character of the plaster such as resistance to shock, nailability, flexibility, composition after setting in the cast or finished form. Since such plaster compositions have strength and similar characteristics of plaster been utilized in making plaster walls or wallboard 10 cmaasntsnteor baendenInhasnuccehdai,wn aays,tihmaptlreeaadnyd wecoornkoambiilcitayl for use in building, efforts have been made in many different ways to render such plaster casts of the set composition is attained. Another and or plaster walls or wallboard more resistant to related object of the' invention is to accomplish cracking and to make these products more re 15 this In such a way th at the mixing and forming operations th at must be applied to the plaster sistant to rough handling and more readily work composition may be readily and easily performed. able in the usual building operations and uses. For example, in wallboard and plaster walls! I t should be observed also th at in some in after they have been put in place, it is quite stances asbestos has been used in plaster. In one -important that the walls be readily workable in 20 such use the asbestos fiber has been added to plaster primarily to improve the plaster work sofar as the pounding of nails and the like into such walls may be concerned. ability or trowelling characteristics while in m an effort to Impart more desirable physical another instance, in the Croce Patent No. characteristics to plaster walls and wallboard, 2,526,066, such asbestos fiber was added as a such as resisfcanre tn ,,A *TM . J r v - " . ' means fIor retaining an expansive component of many difffffeerreenitrtw^aavys or expedients have been 28 Hle pl^ster " W " " " 1 ta Place In each case the amount of asbestos set cast. was quite employed. For example, the plaster composition high, and the water absorptive capacity of the utilized in the making of wallboards has in many asbestos has increased the drying time of casts instances been made so as to incorporate a fairly thus made. large percentage of fibrous organic material such 30 Another important and desirable physical at as sawdust, sisal fibers, paper pulp and the like. tribute in plaster casts, walls, and wallboard is Study of such prior gypsum plaster wallboard indicates th at while these expedients serve to high resistance to cracking due to settling stresses or fire, and to enable a marked improvement to increase the nailability, certain disadvantages are encountered am) rm rH r>ni^ ITW b^e aCttTaainmeeda min respect to this important physical the r e l a t l v e i v T l t h ^ ^ ^ that 38 characteristic of plaster casts and the like is the like that ^ rcentag oi filler or another important object of this invention, to lnstapce? A 00 * and related object is to enable plaster **a * * S ja S S T to te S S : desirable to resist the stresses and strains aSppSlieid a"ndVt.h.e"like. * TMa" * ** m H bood to such structures. When plaster wallboard is put in place on walls Another characteristic that is extremely de or ceilings, it Is secured in place by fastening sirable in plaster compositions th at are used for elements such as nails, clips, screws or the like, building purposes is the workability of the re sulting cast insofar as sawing or cutting may be 45 and the permanence of such fastening is de concerned after the plaster has hardened or been pendent in a large measure upon the shearing strength of the wallboard at its line of engage put in place. For example, normal building con ment with such fastening element. This area of struction in many instances requires th at an critical shearing strength has often constituted soopetnhiantgabne ecluetcitnritcoaal opulatlsetterbooxr pmlaasytebrbeomarmdinwtwani 50 tahnedpiotinist othfefriersfot rfeailaunroethinersuimchpworatlalsntorocbejeilcint gtso, in position, and this opening must in many in so constitute a plaster composition th at plaster stances be cut into the ceiling of a room. In walls or wallboard made therefrom will exhibit a such instances it is found with conventional materially increased shearing strength; and a plaster compositions th at there is a tendency for the plaster to break away from and at an angle 55 related object is to accomplish and expeditious manner. this in a simple to the line upon which the cut is to be made, and I t has long been recognized th at there are , there is also a tendency for the plaster to break many disadvantages and objectionable features! apart into fine dust, and this breaking and dust involved in the employment of asbestos fibers or/ ing, of course, is undesirable, particularly when the work is being done in a home or the like that 6< organic fibers such as sisal fiber, wood fiber and1 paper pulp in plaster compositions and wallboard; is occupied. such disadvantages including the necessity fat Castleman.CERT001391 2,681,888 using added mixing water, with its resulting re duction in strength and increase in drying time for the casts, coupled with the further fact that the organic fibers constitute a fire hazard in a manufacturing plant, and that such organic fibers disintegrate a t relatively low temperatures. Such disadvantages are eliminated under the present invention by affording a gypsum plaster compo sition which utilizes drawn textile glass fibers as a bodying and strengthening component in such a way and with such efficiency as to be economi cally practical and in such a way th a t the rnMn^ and forming, shaping and drying operations in respect to the mixed plaster or slurry may be readily and easily performed. It is well recognized th at the use of plaster or plaster wallboard as a wall surfacing In build ings serves as a protection against the destruc tive action of fire, and many efforts have been made to increase the fire resistant or fire re tardant action of gypsum plaster walls. ef forts have in most instances centered about the character of the lathing employed, while In an other instance a heat-expansive material has been added to the plaster to compensate for heat- induced shrinkage of the plaster in the event of fire, as described in the aforesaid Croce pat wool, and separation of Individual fibers from the mass is quite difficult because of the curled and interlaced or matter relationship of the fibers to the mass. Such separation of individual fibers from the mass is also rendered difficult by reason of the relatively low physical strength charac teristics of the blown fibers which bend quite easily and tend either to retain their bent form 10 orTtohebrderaakwant ttheextbileendg.lass fibers are on the other hand, produced as continuous filaments, each of which is discharged to a molten state through an orifice and is attenuated by winding on a high speed winding drum. In the production, wind tog and handling of drawn glass fibers or fila ments it is essential th at a great many such ex tremely fine filments be grouped into strands each containing from one hundred to several hundred Individual filaments so th at the forces that are necessarily involved in the high speed handling will not cause breakage of the lam en t Be cause of such grouping, the abrasive character of the glass makes it necessary as a practical matter ip apply u, protective-cpatifift t<r &ufih nia-mcnts to prevent" abradKa acTioTThBiw^n rns several grouped 'filaments ~or each "$ t^ rwi am r ent. I t is another important object of the pres protective coating material is usuaily term edthe aecntteIrnisvtiecnstitoon btoe aetntaabinleedhiignhpfliarestreertacordmapnotscithioanrs 30 "inbgonadcitniogn" tmo attheeriaclasaeltohfosuogmhetohfe thacetucoaml mboonndly and products in an improved and simplified man used coating materials such as a starch coating ner, and related object is to attain this result is relatively slight, so th at the fibers or filaments with the minimum of additives so as to thereby may In such Instances be said to be loosely bond enble the maximum ratio of plaster to be used. ed or loosely associated. In other lnumnn*, the At the outset it should be noted th at suggestions coating material may be of such a character as have heretofore been made concerning the use of to hold the filaments of the strand quite perma glass fibers, glass wool or mineral wool in hy- nently together and some thermoplastio resins nraulic cement mixtures" or gypsumTffn^jyrr^- ' when used as the bonding material act to pro- y i e s fur rHfiTSclng or streng^en to g purposes >4,, duce such a strong bond t o the strand. But sucirprtOr suggestions along this line have Tinder the present invention, resort is had to . been found to be unworkable in a m m m m iti tire use of the more costly drawn textile glass sense, particularly insofar as plaster molds, casts, fibers that are loosely bonded or loosely asso walls and wallboard were concerned. This Im ciated and by attaining complete dispersion of practicability of such prior suggestions has re such fibers to the mixture to the manner de sulted from the tendency of the glass fibers or li scribed hereinafter, the full strengthening and mineral wool to form agglomerate masses or h*n bodying effect of each of the individual fibers to the mixed plaster or slurry, as contrasted Is realized with the net effect th at the quantity or with the desired dispersal of the fibers uniformly uroportion of the drawn glass fibers is minimized throughout the mixture. In contrast to such ob and tire use of the costly fiber is rendered prac- jectionable action of glass wool or mineral wool co tieal in. an economic sense. as suggested to the prior art, the present inven The drawn glass fiber component of the plaster tion attains substantially complete and uniform composition is afforded by a small percentage of dispersal of glass fibers to gypsum plaster slurry drawn textile glass fibers cut into short lengths so as to thereby attain a radical improvement to the desirable physical characteristics of the re 0 -ganladssin-fciboerprsorateedOinf the gypsum plaster, and such a character that snri, th .y sulting easts, and this is attained at a relatively A ttain an almost complete or low cost and in such a way as to simplify and fa or the toqirmual filaments' cilitate the manufacturing and other operations involved in the mixing and forming of the slurry. ' ie rcB iuuusl- - .ttom Such drawn glasTfibers, of courseTmayire Glass fibers may be classified generally in two Co of different diameters but are in any event ex main categories or groups as blown glass fibers tremely small or fine. Thus, a fiber having a di or as drawn textile glass fibers, and while these ameter of about 0.00024 inch which is com classifications are based upon the method of pro mercially available, has been found to be highly duction of the fibers, there also are many definite effective as will be described in detail herein- and important distinctions between such groups 65 after. as to physical characteristics and properties of The glass fiber material utilized under the the fibers as well as in the relationship of the present invention is one th a t is loosely bonded individual fibers to each other. Thus, blown glass or associated as fay a bonding material that is fibers are formed by steam blowing of a molten water softenable mn^mfiiLsolupie in charlm-w--- glass stream to attenuate the stream into small ** an d tn e slran'ds arfe flit tllto 1isliuil Iwigffis/witl> diameter fibers, and such fibers take a form in the range of y$ Inch to one inch so as to afford known generally as glass wool or mineral wool to th a t the fibers are not straight and are Inter short sections"or bundles of fibers, each bundle being formed by a cut length of a strand, and laced in a random relation with each other. The it has been found th a t a length of about one- fiber length may vary considerably in such yi 76 half inch is very satisfactory. Under the pres- i Castleman.CERT001392 8,081,808 6 eut invention the binder is afforded by a water present invention attains the desired improve soitenable or a water soluble material such as a ment in the physical characteristics of the re starch tafttoi'lul ui walur sgrj^ablgJcesuuj^jSjr sulting casts, as will be described in some detail It is fOUildTBHt WltH SUChTBm der the individual hereinafter. Th ppw^ntagg hy weight of loosely bonded filaments which make up each bundle or short section of strand tend to remain together in drawn glass fitem agdunder thejpresent lnven- their bundle in the course of a short dry-mixing UHUoUn IaOs fiirvoumt 0ir.0iri8r*r fIKr 1* n-c~>r~r with th e isEn-t*->-T-j-ya-- operation with the other components of the llie composition being afforded by calcined gyp plaster composition, although there is a substan sum plaster, and the length of the fibers may be tial separation of the filaments from their 10 varied between about % inch and one inch, and it bundles as such dry-mixing progresses. is to be understood of course, th at the present in In this short bundle-like form, the strength vention contemplates the use of small added and resilience of the bundles and of the fibers is quantities of retarders, accelerators, starches or sufficiently high to prevent bcreaksing ofr tmhe core adheriveTafitt tLe like in ucepaance with strand or the individual fibers or filaments by 16 USan practice, as well as the addiUon ^of weight the forces th a t may be applied thereto in a mix- reducing foam a^ e" tag operation. Moreover, the strength and ent invention is employed in the manufacture or springiness of the individual fibers and the gypsum wallhoard or like Products, bundles as compared to the forces th at may be For purposes of compartam ^ c o n v e n tio n a l applied thereto in a dry or wet mixing operation 8 gypsum wallboard, w--a-l-lo--o-a-r-d--w-a-s--made ta haU_ w.i*t1h t.h_e p_las.ter i.s sufmficii.ent tio___p_re_v_enit the fommr (innV* IthtieclkmnAeesas Iin aa hbroifaiprHd TpllfatTnlt, Wwith tuhl6e usual mation of swirls, balls or agglomerate masses. equipment to afford four different kinds of board Hnce, in mixing operation th a t is applied to a in substantial quantities, the first of which was a conventional paper surfaced board, identified composition which includes relatively short bundles of loosely bonded drawn glass fibers as SB hereinafter as board A, including 2%% of saw aforesaid is effective primarily to produce uni dust as well as the usual amount of core adhesive, / formity of distribution of the bundles and in and the usual amount of weight-reducing foam. The usual amount of core adhesive Is about 1% dividual fibers throughout the mass of material. As hnereminaboove pominctcecdi ouwti, twhwes udry miixjhinhkg oper- or less of the combined weight of the dr/y consttt- - . . . . . . . o i jjjjg ation does in fact cause separation of individual 80 uWeWnWts, *a*n**d** t**o* the present t--a-r--t-a-n--c-e,'%* - fi_bers or sma-l-l groups of. fib__e__r__saf__r_o___m__11t.heVbunJ d1les, npaenrAcAeMntt Ao#f gffefillfaltHinlllivzfeind BstlAaTrcfihn 1wX7afi.sfi UusSefidfl,. bX ased on but such action is relatively slow so long as the. the combined weight of the dry plaster and saw water soluble or water softenable binder is not dust. subjected to the action of water. Such dry mix Boards B, C and D were prepared with the ing may, of course, be carried on until the fibers SS same paper, and the same core adhesive and have been completely separated from their foam content, but the sawdust component was bundles and completely dispersed to the dry mix, eliminated, and board B contained 0.05% of but this is usually considered unnecessary in view drawn textile glass fiber in V2 inch lengths and of the ease of dispersion to the final wet mix. 4 0 dbiosapredrseCd cionnttahineedmi0x.t1u%re oafs saubcohvefibdeers;crwibheidle: The preliminary distribution of the bundles and individual glass fibers to a short dry mixing oper board D contained 025% of such textile glass ation serves, however, to simplify small batch fiber. By reason of the reduction in fiber content usage of the mixture, as well as to simplify the th at was effected in boards B, C and D, there was wet mTMix*ing operation anda whuenii twhreo water Is fed o--f--c-o--u-r-s--e--a--c.orr,es*po--n--di,ng" in. crease in the amount / Jsoitehs the binder to such an exleutthrt ajreh .' ebni4. n st wiving nrv.rfl.tinu ueifufEied In sawdust component and the use of anaU^quMittties of drawn textile glass fibers in boards, B, c, thes? boards were to all respecte the same R e p a ra tio n of the individual dm w ngiaM flber|JW as the regular board A which was made to serve from ffiar b u n d le f orm sq^ a t ^ ct e ifia ra g u g r " * >tan* ird f . . ..._ _ . d_ trtassTTBwK are almost completely dispersed fii . After the aforesaid boards had been^ made. imifnrm manBanaffoXRMgut^tHe boSyof thfr~' these boards wer" b; ^ * ? *nS!L0iftS^ r I 3 S E ^ S ^ 1 5 T H i ^ e n B t n r V i s a n g l m r . . What empirical tests designed to afford a more tion ttetad frid u ai ^ " f i l M ^ iO r O n ifo n n ly . ns or less numerical basis ~Gcated tfirbtighoutTEeim ssw iaijfhat m ightbe^. ous desirable physical qualities ^characteristics "^rmpd o ra'ndom^disnCTslmT^^-elotlve dire- -- I Os b r -reas e n o T W of such boards. The results of these tests are included in the following table, and the precise ~tgorouEh dispersion an d tfie ra i^ f iie S tlo n s h ip ' nature of the tests will be described following Ofj f g Hirggtion nf tfiBlndlvldusd flbdralfaat tt?e no such table: Board B, 0.06% fiber Board 0 , 0.1% Board D, 0S% Board A, Regular fiber fiber board Whipping T est: N um ber 11 .............. of whips to break. Shock Test: Drop of Weight..-- Small Furnace Test: With 4J4 45minutes plus1.. lb. load midway between Resistance to Crushing by Hammer blow. 10................... U................... 46min. pins... 45 min. plus... satisfactory__ good............... fairly good___ ,, ...d o ............ .......do ......... 7. Binoheg. 16Hnbmtos. goodn. o. Do. Bond B iriUi 0.06% Aim cracked rather bully tn U aboie test. Castleman.CERT001393 9,681,868 8 The whipping test is one th at is quite impor A. S. T. M. Designation E119-50. In such test board D attained a fire resistance rating of 51 tant from a practical standpoint in that it simu lates a condition that is often encountered in minutes, 26 seconds, which far exceeds any rat the handling or installation of plaster wallboard. ing given any half-inch, paper covered plaster board heretofore tested in such a load-bearing Thus in this test the opposite ends of 4 foot by 8 foot sheet of plaster hoard are grasped by two 6 partition fire test. One highly significant fea men and the board is moved up and down so as ture of such test was th at in contrast with the mucking and falling of the plasterboard which to cause the central portion of the board to bow downwardly and then upwardly with what might was always experienced in prior load-bearing be termed a whipping action. In such handling, 10 pwaarltlibtoioanrdste, sbtosaordf oDrdreinmaaryineodnein-htaaclft ianncdhinplpalsatceer any weakness in the board is liable to cause breakage, and by counting the number of whips on the wall or partition at the end of such 51- or up and down movements necessary to break minute, 25-second period, and the failure which determined the extent the rating granted was sisucrheparebsoeanrtda,taivneuomfetrhicealsitnrednegxtihs acfhfaorradcetderwishtiicchs . . based on weakening and bowing of the studs due of the board. . 18 to charring. I t is recognized, of course, th at in plaster wall The shock test was made by supporting a piece board. particularly in relatively thin wallboards, of board one foot wide and four feet long on the strength characteristics are influenced in a three feet centers, and in this instance the grain of the paper extended transversely of the width . large measure by the strength of the paper liners of the sample. A loading board was then placed 20 athned ainctioorndeorf ttoheaffdorradwna bteaxstiislefogrladsestefribmeirnsinign in the center of the span and a sling arrange ment was attached to the loading board. A the absence of such paper liners or the like, slabs weight of 660 grains was then attached to the were made in half-inch thickness and without nHrg by means of a rope. This weight was raised paper liners, in the following table, slabs of up one inch and then dropped and this dropping this kind are shown which were made without fiber content of any kind and with 2% of fine action was repeated through progressively larger distances, the increase between drops being one fibrous sawdust as a fiber, in addition to several different samples including different percentages inch in each instance, and this was continued , n of drawn textile glass fibers cut in half-inch until' failure or breakage of the test board. The u ipngths as hereinbefore described. These sam results of this test were indicated by the number ples of course did not include weight-reduoing of inches of the final dropping movement of such foam, nor did they include core adhesive, but weight. , In the furnace test the board samples were were made solely with gypsum plaster, or with nailed on 6-inch centers to the lower faces of plaster and sawdust or drawn textile glass fibers 0 as indicated in the following table which shows joists spaced on 16-ineh centers and a 4% lb. the transverse strength of the respective samples. load was placed on the board midway between the joists. The board as thus supported formed Results of these tests: what may be termed the upper wall of the fur Table II nace and the temperature developed in the fur 40 nace was substantially 1200 to 1300 degrees F. at Weight Transverse Strength the end of 15 minutes and was thereafter main persq. Oaliper Per Foot tained at 1300 to 1500 degrees F. of Width The nailing test is performed by driving 5 penny cement coated wallboard nails into a wall 45 Lbs. Inch Lbs. board near an open or cut edge, and observing 2.12 0.528 2.04 0.530 5406..11 whether and to what extent the plaster core splits 22..0044 a 630 a 630 50.1 64.5 out or breaks. The first such nail was driven a t a point % inch in from the cut edge of the 2.04 an a 515 0.516 6 69.0 board, and successive nails were driven at points 5 --------- located progressively close to such edge. The break test was performed by cutting one The tests relating to the transverse strength of the board were in the nature of beam tests in paper cover of the board along a straight line which a sample of about 16 inches in length and entirely across the sample, and then breaking to S3 12 inches in width was placed across two knife- determine whether the board would break along a straight line as is desired in use of such board. edge supports disposed 14 inches apart, and a . load was applied gradually by a knife-edge mem The test relating to resistance to hammer blows was performed by striking the boards near . ber to the upper face of the sample midway be tween the two load supports, an open or cut edge and at different distances fo In the foregoing examples and tests it was from the edge, and the quality of the board In observed that the presence of core adhesive such this respect is judged by the extent to which the as gelatinized starch in the commercially pro- core shatters or flies out of such edge in response duced-wallboard samples B, C, and D had the to the blows. effect of increasing the bond of the set gypsum The tests included in Table I show th at as com 65 with the drawn glass fibers. pared with conventional plaster wallboard as rep In all of the examples of the invention it was resented by board A, boards B, C and D attain observed th at at least one desirable characteris a marked improvement in respect to fire resist tic in the cast was enhanced by the presence or ance, while boards C and D attain satisfactory use of drawn textile glass fibers, and this was characteristics in the other testa. 70 particularly true In respect to resistance to the In a fire test conducted on board D, herein above described, at the Underwriters Labora heat of a fire. The advantageous characteristics have been tories, Chicago, Illinois, such board was installed described herein as observed in plasterboard or as the covering on a load-bearing partition and in fliin casts or panels, but it will be evident that tested according to the Standard Methods of Fire 75 these improved characteristics are applicable to Testa of Building Construction and Materials, Castleman.CERT001394 2,681,868 9 10 plaster molding and molded plaster products gen member comprising set gypsum plaster as the erally. major ingredient, and also containing a rein From the foregoing it will be apparent that the forcing Ipgradlant cnnstating essentially Of short, present invention enables gypsum plaster to be substantially straight, resilient, flexible, Individ- bodied and strengthened in a practical and eco 5 ual textile glass filaments, said individual textile nomical manner through the use of drawn textile glass filaments being Individually and uniform glass fibers so th a t the physical characteristics ly distributed throughout said body member. of the resulting casts are improved in many dif 6. The combination recited in daim S wherein ferent ways and to a great and unexpected ex said individual filaments comprise not sub tent. In the ensuing claims, terms such as io BtanHaiiy less than .03% and not substantial "strands," "strand sections," or "bundles," refer ly more than 14% by weight of the total weight to the basic glass textile units which are formed of the gypsum plaster and filament components. in the manufacture of glass textiles, each such 7. A composition convertible by water addition unit comprising a multiplicity of individual glass and mixing to a moldable and settable plastic textile filaments; and the individual filament 13 mass, said composition comprising calcined gyp components of said basic glass textile units are sum plaster as th major ingredient and short denoted by the term "filaments." sections of glass textile strands each composed We claim: of substantially straight, resilient, flexible, in 1. m a method of producing gypsum plaster dividual textile glass filaments, bound into said casts, the steps comprising introducing short sec 0 strand sections by a water softenable binder, said tions of textile glass strands into a gypsum plas filaments lying closely together in substantially ter, each strand section comprising a plurality of parallel relationship in said sections, and the substantially straight, resilient, textile glass fila bonding of said filaments being sufficiently weak ments, said filaments being sufficiently weakly to enable sparation of said filaments from said bonded into said strand section to be capable of 23 sections and dispersal thereof individually ready separation therefrom during agitation with throughout said plaster as an incident to agita said plaster, and agitating said sections and said tion for mixing said sections and plaster in the plaster to reduce said strand sections to their mriittirtnai filaments, said agitation continuing presence of water. 8. A composition as recited In claim 7, where- unta aid inrttaMimi fliamwits are Individually 30 in said sections of textile glass filaments com and uniformly distributed throughout said gyp mise from .03% to 1 % by weight of the total sum plaster. weight of the gypsum plaster and glass filaments. 0. A cast resistant to fire and mechanical shock 2. The method recited in claim 1, wherein said comprising set gypsum plaster as the major in- individual glass filaments comprise not substan tially more than 1.0% and not substantially less 33 gradient, and also containing a reinforcing In than 0.03% by weight of the total weight of the gredient'consisting essentially of short, substan tially straight, resilient, flexible, Individual tex gypsum plaster and individual glass filaments. 3. In a method of producing gypsum plaster tile glass filaments, said individual textile glass casts, the steps comprising cutting Into short filaments being distributed individually and uni- bundles glass textile strands, each bundle con 40 formly throughout said ca st sisting of a plurality of Individual, substantially straight, resilient glass textile filaments bonded together by a water-softenable binder with a suf References Cited in the file of this patent UNITED STATES PATENTS ficiently weak bond to enable separation of said Number filaments from said bundles during agitation for 406,685 mixing said bundles with a plaster and water, 2,198,776 introducing said bundles Into gypsum plaster, and 2,352,201 agitating said bundles in said plaster in the pres 2,425,883 efrnocme osafidwbautenrdlteos tdhirsopuegrsheouintdsiavididpulaalstfeilra.ments 30 2,526,066 4. The method recited in claim 3, wherein the Individual glass filaments comprise substantially Number less than 1% and not substantially less than .03% of the total weight of the gypsum plaster and 49,883 587,556 Name Date Wing ........... . July 9, 1889 JTfnp pt a1. . Apr. 3, 1940 Jacob ----------------- June 27, 1944 Jackson__ ___ ___ Aug. 19, 1947 Croce . ---------- O ct 17, I960 FOREIGN PATENTS Country Date Netherlands______ Feb. 15, 1941 Great B ritain ------- . Apr. 29, 1947 individual glass filaments. 5. I n s plaster board, a body member having paper covers on opposite faces thereof, said body OTHER REFERENCES Ceramic Industry, 56, No. 5. page 40 (1951). * * ar Castleman.CERT001395