Dec. 31, 1946. w. H. COLBERT ETAL 2,413,604 METHOD on PROCESS OF EVAPORATING METALS ' > Filed May 2'7. 1944 /l éW ‘H,K\Au:x Fiji. 5. INVENTORS 2y William H. Colbelft Arfhur R. Wei‘nnch. [WW6 d-m ‘2,413,604 Patented Dec. 31, 1946 UNITED STATES PATENT OFFICE‘ , 2,413,604 METHOD 0R PROCESS OF EVAPORATING' METALS ' William H. Colbert and Arthur R. Weinrich, Brackenridgc, Pa., assignors to Libbey-Owens Ford Glass Company, Toledo, Ohio, a corpora tion of Ohio Application May 27, 1944, Serial No. 537,675 6 Claims. (Cl. 117-107) 1 , 2 Our present invention relates to a novel method or process of evaporating metals. It has to do, more particularly, with the coating or wetting, by capillary attraction, of a ?lament which, for example, may be formed from a coil of ordi nary tungsten wire, tantalum, molybdenum or columbium wire, by various metals in the form minum, beryllium, magnesium, vanadium, bar ium, strontium, iron, nickel, cobalt, manganese, thorium, chromium and titanium, when applied to ?laments of tungsten, tantalum, molybdenum evaporation, to the face .or surface of an ar temperatures should readily evaporate, it has or columbium, will on heating in a vacuum, melt and spread over the ?lament by capillary at traction and satisfactory evaporation of these metals then occurs from the large amount of of an alloy or different alloys, which metal or surface which the molten metal covers. metals it is desired to evaporate and which in However, with a large number of metals which pure form normally ‘do not wet these metallic 10 it is desirable to be able to thermally evaporate ?laments, and the application of said metals or and which from their vapor pressure at elevated metal alloys by deposition resulting from thermal been found ‘di?lcult, if not impossible, to carry out satisfactory deposition of such coatings by metal, plastic, Cellophane, paper, or the like, to thermal evaporation. Thus, for example, silver provide a re?ective or metallized surface coat while readily lending itself to thermal evapora ing for said article. The invention also has to do tion from a. crucible, cannot be evaporated read with securing wetting and with thermal'evapo ily from a coil of tungsten, tantalum, molyb ration of such metals from pure tungsten, tanta lum, molybdenum, or columbium ?laments by 20 denum or columbium when applied to a ?lament of these metals and heated by electrical resist alloying such ?laments by the application to the ance. The silver on melting shows no ai?nity ?laments of the metals desired to be evaporated alloyed with and carrying the elements which " for the metallic filaments and almost immedi ately after melting collects into a drop and falls we have found it desirable that the ?laments be 25 off the ?lament. This lack of ability to wet alloyed with. tungsten, tantalum, molybdenum and colum Methods and apparatus have previously been bium occurs also with the metals copper, gold, employed to apply coatings of metals by thermal ticle, such as a piece of glass, porcelain, plaster, zinc, tin, antimony, cadmium, bismuth, lead, evaporation to the faces or surfaces of such ar thallium and indium. With each of these metals ticles to produce mirrors, re?ectors or metallized materials for other purposes. In these methods 30 the use of the four available coil ?laments as a means of evaporating these metals has not been it is desirable to effect the thermal evaporation possible, and less desirable means of heating of the metal, such as silver or aluminum, by ap have been necessary where it became necessary plying the metal directly to an electrically en to evaporate these under practical conditions re ergized and thus heated tungsten or other me tallic ?lament which is preferably located within a vacuumized chamber. The metals which may be used as ?laments for such evaporations must peatedly in the commercial production of mir rors and metallic coated articles. As each of these metals, after melting, pulls together into is generally prohibitive. While iron and nickel droplets and falls off the ?laments, there has resulted a wastage of the metal‘whenever it has been attempted to evaporate them from these ?laments and there have been continuous fall ures of the apparatus to function due to the loss of the metals from the heated wires; and where any metal has been evaporated the amounts so evaporated have always been uncertain and are of relatively low vapor pressure, they are without control. of such relatively low melting point that ?la ments made from them rapidly burn out. We have found that we may use tungsten, tantalum, molybdenum‘ or columbium as ?la obviously be of high melting point and also of low vapor pressure at the elevated temperatures at which the metals applied to the ?laments evaporate. Thus, tungsten, tantalum, molyb denum and columbium have represented the only practical materials for such use. Platinum also has been used to a small degree but its high cost With these ?laments many of the metals can , ments for the evaporation of metals which do be readily evaporated. Thus, for example, alu 50 not wet these ?laments by causing them to wet 2,413,604 3 4 such ?laments by the application of such ?la ments, or the forming thereon, of alloys of these provided an improved method or process whereby molybdenum and columbium in the presence of temperature is higher and which metal brings about a wetting and coating of the ?lament by a metal desired to be evaporated to form a re~ metals which we desire to evaporate with an ?ective surface coating is applied to a tungsten, other metal which is characterized in that it tantalum, molybdenum or columbium ?lament as will also form an alloy with tungsten, tantalum, 5 an alloy with another metal whose vaporizing the metal we desire to evaporate. As metals which we have found which may be used in a capillary attraction, thus permitting the deposi relatively small quantity which cause the nor tion of the desired metal upon the face- or sur mally non-wetting metals to wet the metallic 10 face of an article by thermal evaporation without ?laments we may use iron, nickel, cobalt, plat appreciable evaporation of the added metal so inum or palladium, or several of these together. as to give a re?ective surface coating showing Thus, for example, we may add small amounts the characteristic properties of the desired metal of nickel to silver and when such alloys are melt only. The alloy element may also be alterna ed on a tungsten ?lament the silver will be 15 tively used in the ?lament to secure the same found to wet the tungsten ?lament and to Spread objectives, as set forth in our copendlng appli itself by capillary attraction over the surface cation, Serial No. 537,676. of the tungsten wires. In the absence of the A further object of our invention is to apply nickel the silver melts, draws itself into a drop to a tungsten, tantalum, molybdenum or colum let and falls oif the ?lament wire because it 20 bium ?lament, a metal such as copper, silver, does not wet the same. Not all metals have been gold, zinc, tin, antimony, cadmium, bismuth, lead, found to act in this manner. Alloying the nor indium or thallium, alloyed with a suitable pro mally non-wetting metals among themselves, portion of another metal which brings about a such as adding lead to silver, does not seem to desirable wetting or coating of the ?lament metal bring about any desirable improvement in the 25 by capillary attraction under the in?uence of wetting characteristic. In each case it is found heat applied to the ?lament and thus permits that the metals of the iron group, namely, iron, thermal evaporation of the metals. nickel and cobalt and the metals of the plat Generally speaking, and in accordance with inum group, namely, palladium, platinum, rho our present invention, the metal to be evaporated dium and iridium readily form alloys with tung 30 which normally does not wet the heater ?lament 'sten, tantalum, molybdenum and columbium is applied alloyed with another suitable metal and also form alloys with copper, silver, gold, providing wetting characteristics to the coils of zinc, tin, antimony, cadmium, bismuth, lead, in a ?lament which may be formed from tungsten, dium and thallium. Thus, the metals of the iron tantalum, molybdenum or columbium. Thus, in and platinum groups which we have enumerated 35 order to thermally evaporate copper, zinc, gallium, readily bring about the desired wetting and it appears clearly that this is accomplished through the mutual alloying tendency which these metals or arsenic, which are metals of the chemical periodic table arrangement found in series 5 or the metals silver, cadmium, indium, tin and possess. antimony, which include metals of series 7, or One of the objects of our invention is to pro 40 the metals gold, thallium, lead and bismuth which vide an improved and satisfactory method or in the periodic arrangement include series 11, all process of evaporating metals which normally do of which metals do not wet ?laments made of not wet heater ?lament coils of tungsten, tan tungsten, tantalum, molybdenum or columbium, talum, molybdenum, or columbium, by alloying we ?rst bring about a satisfactorywetting and the metal so as to cause the metals to wet the adhesion of these metals to the ?laments by ap coils of such ?laments and to coat the coils by plying the metals to the ?laments as an alloy capillary attraction so that thermal evaporation with small amounts of another metal either se can then be carried out. lected from the iron group such as iron, nickel Another object of our invention is to apply to or cobalt, or selected from the platinum group a tungsten, tantalum, molybdenum or colum 50 metals such as platinum, palladium, rhodium bium ?lament a metal to be evaporated which or iridium, and then by energizing the ?lament does not wet such ?lament coils, alloyed with and thus heating it we cause a melting of the a suitable proportion of another metal of the iron metals. It is, of course, well known that the or platinum groups which alloys with the ?la metals copper, silver and gold constitute a family ment and brings about a proper wetting or coat 65 in the chemical periodic table arrangement. ing of the ?lament wires by capillary attraction When the applied metal alloys are thus melted under the in?uence of heat applied to the ?la they apparently alloy to some degree with the ment. metal comprising the heater ?lament wire and As another object of our invention there is by reason of such tendency the molten metals provided an improved method or process whereby 60 wet the ?lament wires and by capillary attrac a metal which is to be evaporated and which tion are drawn out over the surface of the coils. does not normally wet heater ?laments of tung The molten metal which has thus covered con sten, tantalum, molybdenum and columbium is siderable surface of the heated coil and is held alloyed with another metal such as platinum, thereto by capillary adhesion is thereafter evap palladium, nickel, cobalt or iron, and applied to 65 orated uniformly from the heater coils to apply such a ?lament, or in which a suitable alloy consisting of one or more of these metals'with a surface coating of a metallic or reflective nature to an article such as a piece of glass, porcelain, the metal to be evaporated is applied to such ?la silica, mica, plastic, metal, Cellophane, resin, or ments, and by securing a wetting and coating of other support material, by deposition resulting the ?lament by capillary attraction of the metal 70 from the thermal evaporation of the metal from desired to be evaporated may be deposited upon the ?lament. The operations of thermal evap the face or surface of an article, by thermal evap oration may with some of the metals, be carried oration, to provide such article with a re?ective or out at normal pressure but generally are pref metallized surface coating. erably carried out in vacuum chambers known ' As a further object of our invention there is 75 to the art and within a high vacuum, which may 2,413,004. ' . be of the order of one millimeter down to 10 to the minus 5 millimeters or better. It is very necessary that themetal to be evaporated wet and coat the coil surfaces in order that the metal will evaporate uniformly in all directions. By secur ing such wetting action the thermal deposition of these metals, in addition to being made possible, 6 ’ posite ends are attached to brackets 11 mounted upon the supporting posts I! and adjustable thereon so as to vary the position or location of , the ?lament IS with relation to the supporting base Ill. The chamber provided by the housing ll may. if desired, be completely evacuated of air through outlet pipe or conduit Illa-and have a high vacu um created therein by means of suitable air As will be shown more fully later, pieces of the 10 evacuating and vacuum creating means, such as has been‘ found by our process to give uniform coatings. metal to be evaporated and which have been pre Vious’ly alloyed with the metal which brings about the alloying with and wetting of the ?lament, may be hung onto the loops or coils of the ?la ment. The foregoing and other objects and advantages of the present invention will appear from the fol a pump (not shown) . In accordance with one method embodying our invention which is' to be performed or carried out within the chambered housing II, we preferably provide a metal alloy which may consist of silver, copper or gold or other normally non-wetting metal and approximately 5 to 15% or more of platinum. Pieces of this preformed silver and platinum alloy, or copper and platinum alloy, or drawing forming a part of this speci?cation 20 gold and platinum alloy, several of which are shown at I8, in Figures 1 and 2, are bent and wherein similar reference characters designate hung on the loops or convolutions lid of the ?la corresponding parts in the several views. ment IS in the manner shown. _ In said drawing: It is known that silver, copper and gold lend Figure l is a perspective view, partly broken themselves admirably to thermal ‘evaporation but away, illustrating one suitable apparatus for ‘car they have no wetting a?inity for tungsten, tan rying out our improved method or process. talum, molybdenumor columbium surfaces and Figure 2 is a perspective view of a fragment of lowing description and appended claims when considered in connection with the accompanying therefore silver, copper or gold alone is unsatis an electric ?lament showing the application of a factory for coating the ?lament i6 formed from suitable metal alloy to several of the coils or con volutions thereof, and illustrating one phase of 30 either of these metals by a wetting action effected by capillary attraction. Wetting o! the ?lament the method or process of wetting or coating the wire is essential to secure a maximum of evap ?lament by said alloy; and orating surfaces to provide evaporation uniform Figure 3 is a view similar to Figure 2 showing ly in all directions, to the securing of uniform the ?lament after the completion of the wetting deposits, and also to avoid the dropping of the process by the alloy of Figure 2. molten metal off the heater wires. We have Before explaining in detail the present inven found that platinum, while having a higher melt tion it is to be understood that the invention is ing point than gold, copper or silver, readily alloys not limited in its application to the details of con with silver, gold and copper and the alloys have struction and arrangement of parts illustrated in the accompanying drawing, since the invention is 40 a wetting affinity for the four above-mentioned metals, any one of which may be used for making capable of other embodiments and of being prac~ the ?lament I6, and thus platinum lends itself ticed or carried out in various ways. It is to be .particularly well to securing the wetting of the understood also that the phraseology or terminol ?lament by capillary attraction. Therefore, by ogy employed herein is for the purpose of descrip including a certain percentage of platinum, pref tion and not of limitation, and it is not intended erably 5% or more, with the silver, copper or to limit the invention herein claimed beyond the gold to form the alloy IS, the platinum will serve requirements of the prior art. to bring about wetting or coating of said ?lament Referring now to the drawing, we have shown by the molten metal by capillary attraction when a suitable apparatus for carrying out our im proved method or process, as well as one suit 50 the ?lament is energized and thus heated and will act to cause the silver, copper or gold to also cling able metal alloy and the steps of applying the to or wet the ?lament. An early stage or phase alloy or a ?lament by a wetting action resulting of the wetting action of the ?lament I6 by the from capillary attraction. alloy I8 is shown generally at l9, Figure 2. As Suitable apparatus employed by us, and illus trated in Figure 1, comprises, as shown, a sup 55 the wetting action by capillary attraction con tinues, the two metals of the alloy will proceed porting base Ill upon which is mounted a housing, to wet the coils of the ?lament l6 and in fact, shown as a whole at H. The housing Il may be in the form of a bell-jar or the like having a dome-like or semi-spherical top portion or en closed end and a bottom open end having a sur rounding ?ange or projection l2 which is adapted to rest upon the top face or surface of the sup porting base I0. will substantially wet or coat and cover the sur faces of the ?lament. In Figure 3, we have illus trated several of the coils or loops i6a of the ?lament as being coated at 20 .by the alloy from which the pieces l8 are formed. Thus, by includingplatinum with the silver, copper or gold, as an alloy, it is possible, to quickly II, we have shown a suitable work-piece support 65 and e?ectively coat or wet the ?lament l6 by capillary attraction. Since, therefore, the alloy l3 for supporting a work piece, such as a plate or builds up onto the surfaces of the ?lament in piece of glass, plastic, plaster, paper, porcelain, substantially the manner illustrated in Figure 3, metal, or the like [4, in upright position. there will be a relatively uniform coating or wet Located within the chamber and mounted upon the supporting base I0, is a pair of upright sup 70 ting of the ?lament and a uniform dependable evaporation of the silver, copper or gold. Here porting posts l5 between which is carried or sup tofore, when attempts were made to wet the ?la ported, in substantially horizontal position, .an ment by the use of the silver, the copper or the electric ?lament IS. The ?lament, as shown, is gold alone, only small portions of the molten in the form of a coiled wire made of tungsten, molybdenum, columbium or tantalum whose op 75 metal would cling to the ?lament as droplets Within the chamber provided by the~ housing 2,413,604 hanging from the lower ends of the coils of the ?lament, with the major portion of the molten metal dropping or falling off the coils. This was 8 and palladium, such as 5% to‘ 10% of each in alloy with either silver, copper or gold, gives equally as good wetting action as is secured wit particularly undesirable since it was practically impossible to produce, by thermal evaporation, 5 either alone. an even surface coating by deposition, or to con for example, the loops lBa of an electric ?lament or coil [6, such as that shown in Fig. 2, were to trol the deposition to desired coating deposit thicknesses on the surface of an article, such as the article 14, to which it was desired to apply a re?ective surface coating. By virtue of the fact that the silver, copper or gold did not prop erly wet the tungsten or other metal ?lament but had a tendency to drop off said ?lament, the process of coating with these metals by deposi tion was unsatisfactory, slow and painstaking be ' We have also found on the other hand, that if, have applied thereto pieces of pure silver, or of pure copper, and relatively smaller pieces of some suitable wetting and carrier metals, such as plati num or nickel, that when the coil or ?lament is energized and thus heated, whereby to cause a melting of the metals, the molten metals generally drop off the loops before sufficient alloying of these, and alloying and a wetting of the surfaces cause only a small portion or percentage of the of the ?lament occurs, and that the results are ?lament received the metal coating. Consider uncertain and losses of evaporations and mate able shutting down and starting over again was rials and time occur. This is always the case with required when most of the gold, silver or copper the low melting metals such as zinc, cadmium, on ?rst melting dropped off the coils and no 20 tin, lead and indium, which non-wetting metals evaporation was secured. Thus, great waste oc melt quickly at low temperatures and fall oi the curred, the process was considerably slowed down, heater wires or ?laments before any appreciable and the coating produced by deposition, if any, solution or alloying with the higher melting iron was uneven or spotty and unsatisfactory because or platinum metals occurs. Consequently, with of such uneven character thereof on the surface 25 all of the metals we ?nd it necessary and desir of the article coated. Commercial production able to start with a preformed alloy. under such uncertain conditions was impossible. The iron metals are particularly active in al It is to be understood that in carrying out our loying with tungsten and tantalum and the alloys method or process as described above, in the produced are of much lower melting point than is chamber of the housing H, the chamber, de 30 true of the pure tungsten or tantalum. Conse pending upon the metal being evaporated, may quently, we have found that where we apply pieces be at atmospheric pressure, or it may be evacu of iron, cobalt, or nickel to such ?laments along ated of air and a vacuum created therein. Thus, with the metals to be evaporated, or use these as after the pieces iii of the silver and platinum alloy or copper and platinum alloy or gold and platinum alloy, as the case may be, have been applied to the coils of the ?lament l6 and the work piece M mounted upon its support l3 within ?ne wire windings around such metals, that upon heating the ?laments, the iron metals cause rapid melting through the ?laments and breakage of the same which stops or interrupts the attempt to carry out a thermal evaporation. the chamber, a vacuum of 10 to the minus 3 mil Thus we ?nd it necessary to utilize preformed limeters or better, is created and the ?lament i6 40 alloys and with iron, cobalt or nickel, we use is then energized and therefore heated so as to preferably 5% or less, by weight, in the alloys with melt the alloys and to start in motion the wetting the metal to be evaporated as, for example, silver, - action of the ?lament by capillary attraction, as and a weight of such metals as low as 0.5% may explained above. After the wetting action has often effectively be used to bring about satisfac been completed as illustrated generally at 20 in 45 tory wetting of the ?laments. Thus, in evapo Figure 3, the ?lament I5 is further energized .to rating silver or copper by the use of an alloy of increase the heat therein, whereby silver, copper, either with either nickel or iron, we have used or gold in the coating 20 of the alloy will be alloys very satisfactorily which wet the ?laments thermally evaporated and transferred by depo uniformly in which there was 1% to 2%, by sition to the face or surface of the work piece 50 Weight, of iron or nickel present on the weight of I4 which, as shown, is disposed in a position op the silver or copper. .posite the ?lament E6. The platinum does not evaporate at the temperatures required to evap . The use of our metals such as platinum, pal ladium, iridium or rhodium to bring about a satis orate the gold, silver or copper and the re?ective factory wetting and evaporation has been par deposits produced in such cases are of re?ective 55 ticularly attractive in that when used with the values and otherwise similar to gold, silver and metals which it has been desired to evaporate, copper mirrors made by evaporating these metals these metals, platinum, palladium, iridium and alone from crucibles within a high vacuum. rhodium have not appreciably evaporated so that In a similar way pieces of a preformed alloy of the deposits of silver, copper, tin, lead or other silver with 5 to 15% or more of palladium may 60 metals have been secured essentially pure and as have been applied to the heater ?lament coils of tungsten, tantalum, molybdenum or columbium and on heating sush coils the alloy melts, wets mirrors they have shown the full normal re?ec tivity and colors characteristic of pure mirror deposits of these metals. Thus, with silver 95% the ?laments, and thereafter in a vacuum the re?ection value mirrors may be readily secured silver evaporates off the ?lament onto the article 65 when using palladium or platinum with the silver. to be coated and produces a silver mirror of 95 to From the following table of temperatures at which 98% re?ection thereon. The palladium all re the vapor pressure of the di?erent metals is 0.01 mains with the ?lament. Alloys of copper and 5 millimeter, it is apparent that, as these are also to 15% or more palladium are similarly useful the boiling or evaporating temperatures in a vac in preparing copper mirrors and the copper de 70 uum of this pressure, there is negligible chance of posits in their re?ectivity and color show that no contamination of the metal deposits with the palladium is carried over, Palladium alloys with platinum metals since the vapor pressures of these the other non-wetting metals cause these to wet are negligible below 2000“ C. at which the various the ?laments desirably. elements under consideration would evaporate. We have found that using a mixture of platinum 75 On the other hand the use of iron, nickel, or co 2,410,004 9 . halt in the evaporation of gold, copper or tin might be expected to give mirror deposits containing some iron, nickel or cobalt. Moreover, iron, nickel, or cobalt can be used in the thermal evaporation of antimony, bismuth, zinc and cadmium without their contaminating the mirror deposits secured. l0 metals from which the coiled ?lament or element l8 may be formed, other suitable metals may be used for this purpose. We have mentioned these metals particularly since their high melting points and low vapor pressures at the boiling temperatures of other metals as shown‘ in the above table make these the practically desirable - metals for use as such ?laments. Temperatures at which We have described our improved method or _ metal boils melting 1o process as preferably being carried out in a Met?“ A, o m At 760 mm. ‘ mu; ' norma‘iait mosp er c pressure point vacuumized chamber in which the step of wet ting the ?lament takes place. ‘as does also the step of thermal evaporation of the metal to e?ect its deposition upon the workpiece to provide a . °C. re?ective coating thereupon. pressure °C'. 780 321 15 ' 030 > 147 1,380 1,800 2,260 2.200 2.040 2,600 1,800 1,900 2. 300 419 271 Obviously also in the case of the most readily volatile metals, such as cadmium and zinc, the 630 melting of the metals and the wetting of the 327 232 ?laments, as well as the evaporation of the readily 1,615 000 20 volatile metals, such as cadmium or zinc, may be 1,063 659 1,260 1,083 carried out under atmospheric conditions of pres sure if desired, while employing a suitable inert atmosphere. Having thus described our invention, what_we I 2,000 4,300 2,200 4.400 +2,500 +4,100 5.000 3,100 1,480 25 claim is: 1. The method of producing coatings by evap 1,756 1,555 oration of silver from a ?lament selected from 2, 440 the group consisting of tungsten, tantalum, 1,985 molybdenum and columbium, wherein the silver 2,850 3,310 30 is alloyed with a metal selected‘ from the group 2,620 consisting of platinum and palladium and is 1, 950 I heated on said ?lament, and wherein said plati num or palladium causes the silver to wet, to adhere to, and to spread out over the ?lament tance in the thermal evaporation of the various 35 surfaces and by the continued application of heat, to evaporate and to deposit upon an article metals has been secured through our securing good wetting of the ?laments in that the metals to be coated. 2. The method of producing coatings by evap being evaporated show very little explosive boil oration of a metal of the silver chemical periodic ing or spitting which by reason of small chunks of metal blown over onto the article being coated 40 table family from a ?lament selected from the group consisting of tungsten, tantalum. molyb has caused spoilages, This appears to have been denum and columbium, wherein the metal to be accomplished by the decrease of surface tension evaporated is alloyed with‘a metal selected from forces accompanying the wetting and also in the the group consisting of platinum and palladium elimination of conditions leading to super-heat ing by getting the metal to spread out in a thin 45 and is heated on said ?lament, and wherein said A further advantage of very practical impor coating over most of the ?lament surfaces. platinum or palladium causes the metal desired From the foregoing it will be seen that we have provided an improved method or process for ap plying certain metals to a ?lament of tungsten, to be evaporated to wet, to adhere to, and to spread out over the ?lament surfaces and by the continued application of heat, to evaporate and tantalum, molybdenum or columbium by causing 50 to deposit upon an article to be coated. 3. The method of producing coatings on a wetting resulting from capillary attraction articles by evaporation of silver from a ?lament through the application of other metals and ap selected from the group consisting of tungsten, plying heat from the ?lament, and have thereby been able to carry out evaporation of such metals tantalum, molybdenum and columbium, wherein we secure the desirable requisite of wetting of to deposit upon the article to be coated. ' after the wetting action has been completed by 55 the silver is alloyed with platinum and is heated on said ?lament, and wherein said platinum thermally evaporating the metals and have causes the silver to wet, to adhere to, and to caused their deposition upon the face or surface spread out over the ?lament surfaces and by the of a work piece to provide metallized or re?ective continued application of heat, to evaporate and surface therefor. It will also be seen that while the ?laments of tungsten, tantalum, molybdenum or columbium, by metals which normally do not 4. A method according to claim 3, wherein copper is substituted for the silver. wet these, by the use of a platinum group or iron group metal this may be accomplished in sev is substituted for the silver. eral ways. Thus, we may apply separate pieces of a preformed alloy of such metals with one of our platinum or iron group metals and these will wet the pure metallic ?laments. While we have referred to the use of tungsten, tantalum, molybdenum, or columbian as suitable 5. A method according to claim 3, wherein gold ' 6. A method according to claim 3, wherein the platinum present is of the order of approximately 5% to 15%. WILLIAM H. COLBERT. ARTHUR R. WEINRICH.