Document Y9kOExDp6Z3x1R23JLkMNjV68

Circular 6142 June. 1929 INFORMATION CIRCULAR department of Commerce - Bureau of Mines MINERAL WOOL ' BY J. R. Thoe.nen MTC 017134 Circular Ho. 6142 June, 1929. INFORMATION CIRCULAR DEPARTMENT 0? COMMERCE -- BUREAU 0? MINES MINERAL TOOL1 '2 By Ji R. Thoenen EE SCRIPT I OH A1III USES Mineral wool.is a substance composed of very fine, interlaced threads chiefly of calcium silicate or glass--like materials similar in appearance to wool or cotton. Because of the high percentage of air space for a given volume of mineral wool, it is used mainly for insulating purposes. Insulation-has two principal functions; retention (or exclusion) of heat, and sound control- Mineral wool finds a'considerable market for use in high-temperature insulation as a cover for pipe, annealing and baking ovens, and metallurgical and chemical furnaces, and'in low-temperature insulation as stove and fireless cooker linings. Processed'in a different manner it makes an efficient insulator for such uses as filling for house walls and floors, refrigerator lining, and covering fcr .house and underground pipe lines. Used in interior walls and like places, it is an efficient sound deadener as '.veil. Because of its acid-proof properties it is also used as packing for acid carboys and as a filter medium for acids and corrosive liquids and gases. Mineral wool may be divided into two classes - rock wool and slag wool. The differentiation is based on the nature of the raw materials used in its manufacture. Rock wool is made from a natural siliceous limestone (more '^ properly classified, perhaps, as a calcareous shale) found in northern Indiana or from an artificial mixture of silica and limestone. Slhg wool is made from iron blast-furnace slags with or without the addition of limestone to temper the charge. SOURCES 07 INFORMATION Numerous inquiries received by the Bureau of Mines as to the nature and use of mineral wool prompted a study of the material, and in the absence of other than very meager published literature on the subject a field trip was made to the producing plants. This paper presents the data collected during 1 - The Bureau of Mines will welcome.reprinting of this article, but requests that the following footnote acknowledgment be used: "Printed by permission of the Director, U. S. Bureau of Mines. (Not subject to copyright.)" 2 - Mining engineer, U. S. Bureau of Mines. 3 - Cummings, E. R., and Shrock, R. R., T'.ie Geology of the Silurian Rocks of Northern Indiana. Dept, of Conservation, Division of Geology, Indianapolis, Ind., Publication-No. 75, 1928. 5969 MTC 017135 Inf.Cir.No.6142. that field study in December, 1928, and February, 1929, together with informa tion gathered by the author during previous personal contact with the industry. HISTORY OP TKB INDUSTRY .. Little data concerning the history of the industry are obtainable, although Lang^ states that mineral wool has been made for over 50 years. Some years ago a slag-wool plant was operated near Pasadena, Calif., but the author is informed this plant is not now in existence. Also, it is said that there is a plant in Tennessee, but ..no .information is available con cerning it. Rock wool was probably first made at Alexandria, Ind., in 1897 by Mr. C. C. Hall, Manager of the Banner Rock Products Co. Mr. Kail at that time was employed by St. Louis interests as a chemical engineer and manager of a steel plant that was designed and erected under his supervision at Alexandria, Ind. In the search for suitable rock for fluxing purpose? in this plant, the peculiar composition of a local deposit was ascertained. Mr. Hall resigned his position and began experimenting with this rock first to see if it would melt and then to see if it would make a fiber. The abundance of natural gas suggested its use as a fuel, and it was so employed. Mr. Hall's first production of wool was on the premises of the. steel plant, but as this plant was absorbed by one of the steel trusts then forming, Mr. Hall had to move such equipment as he had assembled. At this time he formed with some Alexandria friends a corporation known as the Crystal Chemical Co. This second plant was operated until about 1901 when it was sold to a St. Louis company which ultimately was succeeded by the present General Insulating & Manufacturing Co., with headquarters in St. Louis. In 1906 Mr. Hall withdrew from this company and formed the Banner Rock Products Co., which was incorporated in September, 1906, and has operated continuously since January, 1907. The Union Fibre Co., Inc., for several years operated a small plant at Yorktown, Ind., but they have recently abandoned this site and moved to 'ffaoash, Ind., where they have built a modern plant. 4 - Lang, Herbert, Designing and Operating a Slag Wool Plant. Chem. and Met. Eng., Aug. 27, 1923, pp. 365-367. 5 - Thoenen, J. R., Mineral Wool and Cement from a Si'licified Lime Rock. Rock Products, Feb. 21, 1925, p. 39. 5969 -2- MTC 017136 Inf.Ci r.'.Io ul4i Mineral wool is at rrescr.c- manufactured tv the fcilcv,'ir.;_; ccrr.car.ie: Cc.rcr.r.ies enrlc-;'cd ir. the m.urrafa ctorec f mineral v.u * 1 s Ccrr.paiv' i"--.-1... 'y y.- i-'i'CCAiC-ti3 Co .7.`,-.nvilie Corporation Jchnr-Manville Corporation C-oneiui Insulating & Mfg. Co. union Fibre Co., Inc. (Winona, Minn.) United States Mineral Wool Co. Columbia Mineral Wool Co. Webber Cement Insulation Products Co. Plant location Alexandria, Inc. Waukegan, 111. Kanville, IT. J. Alexandria, Ind. Wabash, Ind. Ketcong, N. J. South Milwaukee, Wis. East Chicago, Ind. number of furnaces 10 1 1 6 2 3 2 1 hi ;-[ [ .7 t L. 1. ' lit. ('ll.'. Rock. Rod:. Rock Si a;;. The Tanner Rock Products Co. has recently been purchased by the Kanville Corporation, and the Columbia Mineral Wool Co. is subsidiary to U. S.. Mineral Wool Co. The plant of the Webber Cement Insulation Prcduo was not visited by the author, but it is understood that this plant oner on slag from a local smelter and its whole wool product enters the marie ingredient of insulating cements. MIKING PRACTICE For the manufacture of slag wool, the slag is leaded fra,-, the c-. either by hand or by mechanical shovel .and transported to the nanu..-..v.tur:1 plant. Some operators have located their wool plants adjacent to old a' dumps and do their own loading. Others buy their slag from the iron sum. which then reclaim the slag from the dump and deliver it to the wool i-n.-.-r Often the material is transported for several miles. So far no woe 1 vLu mown to utilize slag while still molten. The natural Indiana wool rock, cn the other hand, is mined from or quarries. Cummings and ShrockP give a detailed description of the geo! /'/.', occurrence of this rock, and the author^ lias described the general quarry tine. The shallow depths and thin beds of the material favor the use of ! or piston drills, but at least one company lias opened a deposit cf consif thickness and plans to install cliurn drills. Some of the deposits are soft enough to be mii:ed withert blosti'.r Eioewhere as much as 1 pound of explosive n;:y be required per ton ci irf: o - See footnote 3, p. 1. 7 - See footnote 5,.p. 2. MTC 017137 Inf. Cir. Ho`. 6142. ' Overburden is stripped by hand or steam shovel, "he broken stone is loaded by hand or shovel and conveyed to stockpiles, where it is stereo, during the winter season to obviate mining except in summer. liOIFACTUimiG PRACTICE Handling Materials Both rock and slag are melted in cupolas, very much like oast iron. To convey the raw materials to the- tops of the cupola's various moans are employed, among which may be mentioned bucket elevators, elevator and oars. Coke is the usual fuel- employed, and is charged in* alternate ]a;ors v ith the slag or rock in the tops of the cupolas. The charge is proportion-.-! at cone plants by counting the shovel's of each material; at others monorail b,; tare used, and the charge is proportioned entirely by weight. Cunola Practice The cupola in almost universal use is of the vertical-cyl\n*i-_>r wnU-r- jank-'-tefi steel type, roughly '?k feet in diameter by 16 feet in height, B in tuyeres are placed about two feet above the bottom, and the molten material iru-vn off near the bottom through a fire-clay lined opening. Air is i i.u tnrough the tuyeres by blcwer fans at low pressures. Tne bittern of tne vv i.< is arranged with drop doors to facilitate cleaning. The water-.iaci-at-h >el. s -.re raid to have a capacity of 1,0C0 pounds of wool per hour and .-.re : perk, o-i coat ii.uously six days per week when in production. Brick cupolas of the same general dimensions have bf-.-u. u 1 L.; ! -i cand are at present used by cne company. The brick units ro.i.-rite > nly i a. !. the 2-i hours, and repairs to the lining are made while tne cv.cu.Ln are idle. In seme instances the water-jackets are used to- generate cler... i-.-r power purposes and for wool blowing. Blowing Wool The molten material issues from the bottom of the cupola.- in a sr.-.l L stream, the flow and temperature of which are carefully regulated. The La. as it falls is broken up by a steam jet (at 80 to 100 pounds pressure) into minute balls or shot , which while still in a molten condition are propel led rapidly through the air. In passing comet-wise through the air, fine thro, -ic of glass-like material form as tails to the shot and fall ir. a fluffy muse on the floor of the wool room. The best form and chape for the steam-jet blower is a subject of con siderable controversy among operators. Th .arious operators advocate their own particular design and maintain more or less secrecy concerning its d"tails. 5959 - 4- MTC 017138 ly speaking they are all sc <-- ranged as h which receives the fallir Isc. (iOC Tne wool "blown into the wool rccir.s is gathered either ly hard c r or. r belts, for further processing. Seme operators arrange two wool rooms tor each cupola, so thus wool olcv/n into one while being.gathered by hand free.; the other. Gcoer-o c room and gather the wool v/hile the cuocla is down for ruruir:;. k- -.ractice involves continssens .blowing into a single wool run, : is formed by a moving conveyor belt which gathers the wool :-m.at ells, and passes it on"for further.processing. .FINISHED PRODUCTS Loose wool is the sole product of several plants and finis r a loose insulate p.g materia?, i s required. kino. aL loos form as a filter ny-dium for aci he and corrosive ^.as.e ;aelci arcur.d acid carboys for shipment. Loo e -wool is run through machines termed "granulatero te break the sunt li-mi the fine threads and remove j f in a short-fiber, shot-free wool which is used f nr.e rials in the maun fa ''tv ' j of insulating cements. This- mu; .. cntenoivft]y as iusice 1. culation. The granulated woei i". M cure into the space.-.; Leu,non the ctuviiag and ,icists (-f bfls ''n;itr.j.cted and forms a very effective- heat and sound ins-ni.a addition to the method of using granulated wool for ho.u.e i net-id,- raw wool is placed . ;;v,eea wire netting such as vu chicken wire, or chi:-Lon v; ire and metal lath. These "bla h. .h varucu sices ani thicknesses to suit consumers and for house ; placed directly c n the stud-lings or between them. Where metal lal f-.i on.- side, the lath ic plastered in the usual manner. Similar <n- re rrsvle for re f rigo :utor and cu-ld-roo::: linings, x-iankets arc aicr. u Lor and oven cover:a -s, au-i are in turn covered by innula-t in,; cement for outdo or tar.-:.; in vh.ich 1 i quids must l>e kept above freer in is use for this class of fabrication. Used in blankets or as Ic-'-se wool the material is said to oe c-f gr in co ntre 11 ing tne a ecu:-, tic prepevtios oi buildings, and in vu.-huh us email machinery unit:; -.--ic.li an house refrigerator motor:-:, etc. Probably the greatest use for raw and granulated wool is in th o ; -.. of " reck wf or " ro-r.k felt." Blocks of this material are urn o ; sices a'..- un,ij,;.ucs for r-_-f' gemu tor lining. haw or nraiv.-.h. led : with other ingi u vents and v.v. if; s binders, is mixed -with v--..t- r MTC 017139 Inf. Cir.ITo.cl42. a stiff said, and is placed on pallets and subjected to leu pressure. Tv.ese pallets are then run on racks into drying rco.cn and dried in a current cf hot air. (This material is also melded into forme for pipe cr wring and is cove re 1 v.itn cotton. Often it is reinforced with ci:ideen wire. High-1e-upenature insulation is made frc.c a mixture of refractory bind ers r.-i th the wool; the whole mixture is compressed into blocks or tridr. :T.-h .-rat erial is used for covering glass and metallurgical furnaces, annealing v.i enameling ovens, and for pipe covering. Various grades of raw wool are sold, depending on the consumer's specifies.* ;ons. No standards have as yet teen set up. Seme consumers demand tad wool shall te oiled, whereas others require that it te dry. Prices d-no; d n competition with similar insulating materials and ever, for similar r.u. i.r, are liloely to vary in different contracts. The following prices are indicative only: law wool - $20 to $25 per ton. C-ranulated wool - up to $40 per ton. `'flex felt" and "blankets" - 8-10 cents per board foot. Block - 15 cents per board foot. Cork board - 7 cents per board foot. Pine covering - Standard 35 per cent magnesia list, less 50 per cent. brick - $100 per M. DESCRIPTION OE PLANTS There are many elements in the manufacture of mineral wool which must be classed as secret trade practices. Therefore the following description of plants must be confined to more or less general information to avoid disclosing private practices. Johns-Manville Corporation Banner Rock Products Plant, Alexandria, Ind. The Banner Rock Products Co. operates a large open quarry of wool rock winch is covered by 3 to 5 feet of clay and loam overburden. Stripping in done by steamshovel and drag line. The wool rock attains amaximum thick ness of 15 to 20 feet and tapers in all directions. The rock is drilled with steampiston and air hammer drills, blasted with. 40 per cent gelatin dynamite, and loaded into small quarry cars by hand and steam shovel. Loaded cars are tramrAed to the foot of an incline and hoisted to a storage pile adjacent to the kilns or cupolas. 5969 -6- MTC 017140 The manufacturing plant consists of the original four-cupola installa tion and a new modern six-cupola plant. In the old part of the plant the cupolas are charged by hand, but in t: new plant raw materials are brought to the charging floor by an overhead traveling crane which deposits the ro.ck and coke in alternate bins near the tops of the cupolas. A traveling bucket operating on a monorail is leaded by hand from the various bins, weighed, and dumped into the hoppers over the cuoclas. The cupolas are all of the standard, vertical, steel-cylinder, waterjacketed type. Draft is furnish, i by blower-type fans. Owing to the karduesc 01 the local water, it must be treated before circulation through the jacket;.. In the cld plant the wool is blown into alternate wool rooms from ea'-h cupola, bat the rooms in the new plant are fitted with sloping sides and a narrow conveyor belt at the bottom. This insures automatic and continuous collection of wool. Arrangement a are such that the finished wool can be sent on conveyors rect to fitting tables for fabrication into blankets or to granulator;; and whence by elevators to the mixing tanks for the preparation of rook c-..-rlc. The whole new plant is designed to utilise all possible automatic tn::: -.'tat ? .,-n devices and than insure constant and cor.tiinu us ope rat ion with a of labor. '. 1 The plant employ:; approximately SCO nan, and has a potential capacity pour.as c f w.;ol nex' houi*. waukegan, 111. The equipment of the plant at Waukegan consists of one standard wnterjackotec. cupola and operates on slag obtained from an iron blast furnace at keyvi lie, Wisconsin. Composition of the slag was given as: per cent SiO................................ 30.0~ -3n..0e>............................ ALAn/0'.J,........................... CuO........................... i.hgo........................... s................................ 1.0 11.0 20.0 io.o o.5 - o. a MTC 017141 Inf.Cir.-tfo.6142.-' Occasionally the charge must be tempered with other raw materials to insure the correct chemical control. The cupola is charged by hand, and the blowing practice is standard, tfo fabrication is attempted except in the form of blankets. Plant capacity is 1,000 pounds of wool per hour. Manville, H. J. ' The plant at Manville, N. J.f also uses slag as a raw material. Although the plant was built as a production unit, it is now used primarily as a technical experimental plant. The raw materials are charged into the single standard cupola from overhead bins and the wool is blown into a vertical-sided room.in which the . floor is a conveyor belt. A short conveyor belt takes the blown wool from the collecting conveyor for sacking. tfo fabrication is attempted at this plant. Plant capacity is 1,000 pounds of wool per hour. General Insulating & Mfg. Co., Alexandria. Ind. The plant of the General Insulating & Manufacturing Co. at Alexandria, Ind., was described by the writer in the February 21, 1925, issure of Rock Products. and the reader is referred to that article for a detailed account of operation. The plant operates on Indiana wool rock from nearby quarries. water-jacketed cupolas are used, and various products are fabricated. has a potential capacity of roughly 6,000 pounds of wool per hour. Six The plant United States Mineral Wool Co. Columbia Mineral Wool Co., South Milwaukee, Wis. The Columbia Mineral Wool Co. at South Milwaukee, Wis., likewise uses slag from the Mayville Iron Co. as raw material," but both Mayville dolomite and red granite are added with the slag in the cupola charge to obtain the correct chemical control. . The wool is blown from one standard water-jacketed cupola, using a fan-type blower for cupola draft, into alternate wool rooms and collected by hand. tfo wool is fabricated at this plant. Capacity of plant is 1,000 pounds per hour." 5969 - 8- MTC 017142 I Oil Oi-xJ. *.6 w cc r.g, , J The U. S. Mineral Wool Co. operates cr.e brick cupola at Ns tec r.g, J., f; r 16 hears- daily* During the idle B hours the cupola is entirely relir.ed with a local clay and the wool is removed fre.m the blowing room. A second brick cupola and also a standard water-jacketed cupola are available but were net operating at the time of the author's visit. At this plant both rock and slag wool are made. The slag is obtained from abandoned dumps of the Replogle Steel Co. Raw calcite is added to the slag charge to control the proper mixture. For making rock wool, silica rock and crystalline calcite are purchased from nearby sources. The fuel charge with these raw materials consists of a mixture of anthracite coal and coke. With the slag, coke is used alone. The blowing operation is similar to that already described, and the wool is collected by hand from the blowing chamber. No wool is fabricated. The plant capacity is 1,000 pounds per hour for 16 hours daily with one cupola. Operating the three cupolas, the potential capacity would be tripled. Union Fibre Co., Inc., Winona, Minn. Wabash, Ind. The Union Fibre Co., Inc., recently transferred its operation from Yc-rktown, Ind., to Wabash, Ind., where a modern plant has been erected. The raw material used is the Indiana wool rock, quarried near the plant. This company was particularly fortunate in its quarry site, as previous to their advent a former company had operated a commercial stone quarry on the property. This operation had removed not only the overlying clay and loam sur face but also a layer of hard limestone, and as a result the wool rock was stripped and exposed over a large area. In this particular locality, moreover, the wool rock apparently attains its maximum thickness in the State. The face, as exposed in the quarry, has a vertical height of roughly 60 feet. Future plans are to operate the quarry with churn drills, cariying the face the full height of the deposit. At present, air hammer drills are used on shallow benches. The stone is blasted with 40 per cent dynamite and loaded by hand into small steel quarry cars, which are hauled up an incline and dumped on the charging floor above the two steel water-jacketed cupolas. Cupolas are charged by hand with rock and coke, and the wool is blown by steam in the usual manner. Tire plans call for installing additional cupolas when the demand requires. 5969 -9- MTC 017143 Ir.f. Cir.IIo.6142. . Considerable study is apparent- in- the design of the blowing roua and m the sac sequent processing of the '.reel. The clow roc;:; i tseif.-cas vertical c: narete side walls. 6 feet apart, and the floor is a conveyor beat wnira, heinj. inclined, also acts as an elevator and carries the blown wool tns full ien.-;tn cf the slow room to the tep of the factory. Ingenious devices in the process enable the wc-cl to re ntrolle--. v:ufcraly for thickness and density ever the full width cf the cr.nveyc r. .Ac t:.v w.,-,,i co:r.as from the blowing char.her in a continuous blanket cf predete:r..ir.c.i thickness and density it is discharged onto a descending conveyor who re iv. si Ltiir.g unives divide it into v;laths 'convenient for different neon and f r rolling up at the lower end into rolls. These can then be wrapped in . -d \ suitable machinery in a manner similar to the wrapping of cotton tact in:. The wool is not as yet fabricated into ary product other than the 1 in abet Am, although future plans call fc-r such fabrication as markets nog :u quire. The potential capacity of the plant is 4,000 pounds per hour. DISCUSSION 0? TECHNICAL PHASES Ce no ral Mineral wool is manufactured by first fusing the necessary raw niator Inis to a liquid slag and t..sn blowing this molten slag into wool. The resulting wool, whetner made from blast furnace slag, natural rook, or a combination of raw materials, is essentially the s.ame for all inurhou purposes. Technically, this statement may be disputed for the reuse-a tint 'riant-furnace slags often contain srra.ll amounts of sulphur which if present in the -sulphide fora in wool, would have a tendency to corrode ary metal s.uui as reinforcing metal, oven-sheathing, water pixies, etc., with which the wool mi/li rrao ir. contact. However, since rock wool also is likely to contain t.ns element, (originally in the fuel) such wool might be objected to on the same frounds. In ary event, sulphur may be considered detrimental only when it is present in the sulphide fora. If it bn entirely oxidised to sulplsto the cb.f ;:m.oalul action is greatly reduced jf not entirely eliminated. In this connection it is interesting to note the results cf ernerimnn+s by various inv-utipatorn a.; reported by the national Slag Association.** Tnese experiments, as listen by the association, indicate that slag wool has no corrosive action m steel inclosed within it. On the other hand, manufacturers of rock' wool claim this is the fundamental difference between rood: and slag wools. In the writer's opinion this matter of sulphide and sulphate content is a pertinent oxibject for research oy wcol manufacturers, as it embraces the whole question of raw materials. h - TTnt tonal Slag Assoointion, Is There Ary Corrosive (Quality in Slag. Symposium No. 10, 927 Leader Fldg., Cleveland, Ohio, 192S. u9'-.j - 10 - MTC 017144 0 ir *o. 61 Charge Che cupola charge varies greasly in different plants. As Fuel is of LA:- major constituents of the charge and probably the moot expensive, : .-.r.l for pea.id, its consumption is of great economic iirpertance. Ir. this r.-r.:.:Lieu it is interesting to note the great variation in fuel ratios as ,.ud in the plants visited. In order to avoid exposure of individual ope ra ts-os, ratios only are given, without hey to plants. Variations in Fuel Ccnsurmtiqn at Different Plants (Tons slo.g or roch.meJ-ted per ton of fuel used) ' Pock plants Slag plants 3 3.5 1.3 2 . 5 1.9 1/ . 2.1 - ' 3.7 " ' ' ' 2.8 2/ 2.8 2T 1 - Includes a small addition of cote. 2 - Unweighted average of four plants. Those rather wide variations in fuel efficiency obtained "by-dl/herenc cerate rs indicate the need for careful study of-this problem. One operator reports maximum and minimum limits for wool root: analyses to produce good wool as follows: ha,: iron, . . . hr aim;;:: . . . Si02 34.23 28.28 pe23 AloUr7 11.54 10.00 OaO 15.80 23.10 MtgO 10.93 8.63 C02 21.SO 18.14 Typical analyses o f slags u red in making mineral wool are as follows: Si02 38.0 33.4 Fe,,0,., 1.0 0 < A123 11.0 10.5 CaC 28.0 31.5 kgO 19.6 15.3 S .5-.8 l.o An analysis of roc.I-: wool ao obtained seme time ago was as follows: SiO 42.84 A* 3l 0^f,(7 Tip 0 * 23 1.40 CaO 51.74 y.rfi S Unde te mined pLu 7t ^X.) 0.0 1.27 While slag, either by itsel f or mixed with limes tone, and natural wool reel: are the two principal raw materials used , at least one manufacturer produces wool from silica rock and oalcite. 3y proper chemical control, wool can te made from a number of materials. 5369 - II - MTC 017145 Inf. Cir.'!o.5142. Temperature Control The fusion temperature.obtained in the cupolas is reported as ranging from 2,800 to 3,000?, 'There are no d. ta as to whether the temperature or the time required for fusion varies with different raw materials. One operator, however, reports that wool rock obtained on the surface of the quarry is easier to fuse than that at seme distance below the surface. At this quarry the sur face rock presented a yellowish color while that below was blue, indicating that changes due to alteration by descending surface waters may have a bearing on fusibility. Blowing Wool Irrespective of the temperature at which the materials fuse, the temperature or at least the fluidity of the.issuing stream of slag is of the utmost importance. The quality of the resulting wool v,ith regard to amount cf shot contained and length and flexibility of threads, depends on the temperature of the slag stream when it encounters the high-pressure steam. Careful research into several phases of this step in the:operation will undoubtedly prove fruit ful. Mention may be made of the following: 1. The relation between the slag temperature'and the length of fiber. 2. The relation between the size of the slag stream and the quality o-" "*-0 Vi 0 c 1 3. The jiation between the .emperature of the slag ar.J. the temperature and pressure cf me stoam. 4. The relation between the iuality of the wool and the air currents :.st up in the wool room by the blowing operation. Or.o plant visited several years ago by the author used compressed air Instead of steam ir blowing a slag wool. The wool produced ex .isited extremely -u/ug fibers, but i is net known whether this was due to the use of air instead of steam or to the composition or temperature cf the slag stream. C-illection of Blown fool Recent progress in the industry indicates a decide., t end toward mechanical and automatic handling of the product and a decrease in manual labor. Tnis result is in line with the mechanical progress of the times; however, while considerable progress has been made, there are many problems yet to be sclvnd. 1't is interesting to note the various ways in which ' fferant operate:-;; ;e using automatic conveyors to eliminate hand collection. Production and Productive Capacity Available production statistics are summarized in Mineral Iniuot:7 for 1911 as follows: 5969 - 12 - MTC 017146 Inf. Cir.lie. 6142. Production of Mineral Wool in the United States (In tons of. 2,000 pounds) Year Amount Value Per ton 1900 6,002 $60,2 ID $10.05 1901 6,272 68,902 11.00 1902 1903 1904 1905 10,843 (1) (1) 6,164 105,614 ---- 69.560 9.67 ----- 11.28 (l) - No statistics collected. Year 1906 1907 1908 1909 3.910 1911 Amount 5,375 9,008 9,197 11,626 8,408 7.514 Value $55,550 81,769 77,228 101.621 84.012 65 ..500 Per ton $10.33 9.08 8.40 8.74 9.99 8.72 Although no actural figures for mineral-wool production appear to have teen collected, the industry seems to have grown considerably since 1911. The 24 cupolas listed in the eight plants now operating have a potential capacity of 24,000 pounds of wool per hour. On the basis of a 200-day year, and allow ing 24 hours per day for 22 cupolas and 16 hours daily for the two brick cupolas, the total annual production capacity can be calculated at roughly 54,400 ter. . TThile this estimate is doubtless excessive, the output is evidently several times greater now than in 1911. 5969 13 - MTC 017147