CA1090576A

CA1090576A - Method and apparatus for reducing deposition of volatiles from glass

Info

Publication number: CA1090576A
Application number: CA261,883A
Authority: CA
Inventors: George R. Machlan
Original assignee: Owens Corning Fiberglas Corp
Current assignee: Owens Corning
Priority date: 1975-10-21
Filing date: 1976-09-23
Publication date: 1980-12-02
Also published as: BE847327A; NL7611460A; JPS5259727A; IT1068906B; DE2647178A1; DK476476A; SE7611572L; ZA765788B; NO763584L; FR2328671A1; FI763009A; NO139781B; ES452564A1; NO139781C; BR7606904A; GB1524887A

Abstract

ABSTRACT OF THE DISCLOSURE

A method of processing heat-softened glass comprising flowing streams of the glass from orifices in a stream feeder includes the steps of attenuating the glass streams to fibers.
Heat is conducted away from the glass streams through metal members adjacent the glass streams. Streams of gas are directed above the metal members for reducing condensation of volatiles from the glass streams on the metal members.

Description

`- 109()57~

The invention relates to a method of processing fiber form-ing mineral materials and to apparatus therefore.
Heretofore textile glass compositions have usually includ-ed boron and fluorine compounds. The fluorine in the glass tends to minimize the deposition or accumulation of compounds from vo-latiles emitted from the glass on the metal members or fin shields conventionally employed for conducting heat away from the glass streams to render the glass streams of a viscosity suitable for attenuation to fibers.
By reason of environmental restrictions pertaining to air pollution and contamination, glass compositions for forming tex-tile fibers or filaments are being employed wherein the glass compositions contain boron but little or no fluorine. In employ-ing such fluorine-free glass compositions for forming streams of glass for attenuation to fibers, the major chemical species in the high temperature environment at the stream flow region is boric oxide.
The vapor pressure of boric oxide B2O3 decreases very rap-idly with temperature so that the boric oxide condenses on the fin shields resulting in a comparatively rapid buildup of solid boric oxide on the fin shields. This condition necessiates freq-uent cleaning of the fin shield assembly to remove the accumulat-ed condensation products from the metal fin shields or members.
In the absence of a substance such as a fluoride to reduce the vapor pressure of boric oxide B2O3, the beads of glass form-ed at the orifice projections during start-up tend to be large in diameter and comparatively short due to the lower viscosity and surface tension of the glass surface. Such beads of glass contact one another and the metal fin shields causing flooding of the glass over the underside of the stream feeder floor sur--109~157~

face.
It is an object of the present inventlon to obviate ormitigate the above disadvantages, According to the present invention there is provided a method of processing heat-softened glass comprising flowing streams of the glass from rows of oriflces in a stream feeder, attenuating the glass streams to fibres, conducting heat away from the glass streams through heat absorbing members adjacent the glass streams, conveying heat away from heat absorbing mem-bers by a cooling fluid, and directing streams of gas above andin substantial parallelism with the heat absorbing members to react with a primary gas supplied by streams of glass to form a secondary gas and maintaining the heat absorbing member above the condensation temperature of the secondary gas to reduce de-position of condensation products of volatiles from the glass streams on the heat absorbing members, According also to the present invention there is provided a method of processing heat-softened glass comprising flowing streams of glass from rows of orificed depending projections of a stream feeder, attenuating the glass streams to fibres, conduct-ing heat away from the glass streams through metal members adja-cent the rows of glass streams~ and directing streams of gas from regions adjacent the sides of the stream feeder into impinging re-lation at zones between rows of the dependlng projections to react with a primary gas supplied b~ streams of glass to form a secon-dary gas and maintaining the heat absorbingmember above the con-densation temperature of the secondary gas to reduce condensation of volatiles from the glass streams on the metal members.
According to another ob~ect o the present invention there is provided apparatus for processing fibre forming mineral mat-erials comprising a stream feeder having a plurality of orifices .-2~

1090~76 therein for generating streams of materlal, heat absorbing mem-bers arrayed between and below the orifices and gas introducing means for introducing gas above and ad~acent the heat absorbing members to inhibit condensatlon of volatiles from the streams of mineral material on the heat absorbing members.
According to a further aspect of the present invention there is provided apparatus for processing heat-softened glass including a stream feeder containing heat-softened glass, the feeder having transverse rows of depending projections, the pro-jections having orifices to permit flow of streams of glass fromthe feeder, means for attenuating the streams of glass to fibres, a plurality of heat absorbing members arranged in side-by-side parallel relation, each of the members disposed between rows of glass streams flowing from the stream feeder, manifold means ad-jacent the stream feeder and a plurality of nozzles connected with the manifold means, each of the nozzles being disposed to direct a stream of gas above and in lengthwise relation with the adjacent heat absorbing member According to a further aspect of the present invention there is provided the method of processing molten glass compris-ing supplying streams of molten glass, conducting heat away from the streams by a member adjacent the streams, reacting a gaseous fluid with a primary gas supplied by the streams of glass to form a secondary gas, and maintaining the temperature of the member above the condensation temperature of the secondary gas to reduce the tendency of the secondary gas to condense upon the member.
The invention further provides the method of processing heat-softened boron-containing glass comprising flowing streams of the glass from orifices arranged in rows on the floor of a stream feeder, attenuating the glass streams to fibres, conduct--2a-109()S7~i ing heat away from the glass streams through members adjacent the glass streams, directing streams of gas reactable with boron-containing volatiles adjacent the heat-conducting members, react-ing the gas of the streams with boron-containing volatiles from the glass resulting in a gaseous boron compound and maintaining the temperature of the heat~conducting members above the conden~
sation temperature of the gaseous boron compound to substantially eliminate condensation of the compound on the members.
Further according to the present invention there is pro-vided a method of processing molten glass comprising attenuatingstreams of the glass into filaments at a first zone~ conducting heat away from the streams b~ a member adjacent the streams at the first zone, directing a first gas into the first zone in a reactable relationship with a second gas supplied to the first zone by the streams of glass to form a third gas~ and maintain-ing the temperature of the member above the condensation tempera-ture of the third gas to reduce the tendency of the second gas and third gas to condense upon the member.
Preferably the gas introducing means includes a pair of nozzles disposed in spaced aligned relationship so that a stream of gas from one nozzle impinges upon a stream of gas from the other nozzle. The supply of a gas in the region above the metal fin shields or members adjacent a glass stream feeder promotes volatilization of boron compounds from the glass and thereby re-duces or substantially eliminates condensation of the boron com-pounds on the fin shields or members~
An embodiment of the inventlon will now be described by way of example only with reference to the accompanying drawings 2b~

lO9VS76 in which:-Figure 1 is a side elevational view of an arrangement forprocessing glass for the production of continuous glass fibers in accordance with the present invention;
Figure 2 is an enlarged sectional view of a portion of the stream feeder, the view being taken substantially on the line

2-2 of Figure l;
Figure 3 is a transverse sectional view through the stream feeder and associated components, the view being taken substan-tially on the line 3-3 of Figure 2;
Figure 4 is a schematic plan view of the stream flow sec-tion of the stream feeder and the gas distributing system associa-ted therewith, and Figure 5 is a fragmentary sectional view of a portion of a stream feeder illustrating the formation of beads of glass at the stream flow orifices during start-up.
While the method and apparatus of the invention provide a gaseous environment having particular uitiliy in processing glass for forming fibres, it is to be understood that the method and apparatus may be utilized in the processing of other fibre-forming mineral materials.
Referring to the drawings in detail and initially to Figure 1, there is illustrated a stream feeder or bushing 10 adapted to contain heat-softened mineral material, such as glass. In the embodiment illustrated, the stream feeder 10 is connected with a forehearth 12 which conveys molten glass from a melting furnace (not shown) into the stream feeder. If desired, heat-softened glass may be supplied to the stream feeder from a melter in which pieces or marbles of prerefined glass are reduced to a molten condition.

~09OS76 The stream feeder 10 is fashioned of a metal or alloy capable of withstanding the high temperature of molten glass, such as an alloy of platinum and rhodium. The feeder 10 is pro-vided at its ends with terminal lugs 14 for connection with cur-rent supply conductors (not shown) for passing electric current through the feeder to maintain the glass at the desired tempera-ture and viscosity for flowing streams of glass from the feeder.
The floor 16 of the feeder 10, usually referred to as a tip section, is formed with transverse rows of depending hollow projections or tips 18 providing passages or orifices 20 through which flow streams 21 of molten glass from the feeder. The glass streams immediately below the projections 18 are in the form of cones 22 of glass.
The glass streams 21 are attenuated into continuous fibres or filaments 24 by winding a strand of the fibres or filaments into a package. In the arrangement illustrated in Figure 1, the continuous fibers or filaments are converged to form a multifila-ment strand 26 through the medium of a gathering device or shoe 28. The strand is wound into a package 30 upon a collector or forming tube 32 mounted upon a mandrel 33 rotated by a suitable motor (not shown) contained in a housing 35 of a winding machine of conventional construction.
` As is conventional in winding textile fibres or filaments into a package, the strand is traversed lengthwise of the collec-tor 32 to build the package of superposed layers of strand by a rotatable and reciprocable traverse means 37. The traverse means 37 may be of the character illustrated in the U.S. patent to Beach 2,391,870 which engages and oscillates the strand to effect a crossing of successive convolutions of the strand on the collec~
tor in a conventional manner. A lubricant, size or other coating 109~7~

material may be applied to the filaments by engaging them with a roll applicator 39 mounted by a receptacle 40 containing the size or coating material Disposed adjacent and lengthwise of the stream feeder 10 is a header and fin shield assembly 42. The assembly 42 is inclu-sive of a tubular header 44 having an inlet tube 45 and an outlet tube 46, the header accommodating a circulating heat-absorbing or heat-transferring medium, such as water. Welded or otherwise joined with the header is plurality of heat-transferring metal members, fins or fin shields 48.
It is preferred that the fins or members 48 in their oper-ating position are disposed with the upper edge S0 of each fin or member at a level slightly above the extremities of the tips or projections 18 as shown in Figures 2 and 3. Heat from the glass streams is transferred to the metal members or fins 48 and the circulating cooling medium or fluid in the header 44 conveys the heat away from the glass streams. Such arrangement is of conven-tional character and functions to convey sufficient heat away from the glass streams to render the glass of the streams at a proper viscosity to facilitate attenuation of the streams to fibres or filaments.
Textile glass compositions have heretofore included such constituents as boron and fluorine. The environment above the fin shields at the region of the feeder floor in prior fibre-form-ing operations is nearly quiescent or stagnant, the environment being composed of air, volatiles from the glass and their reac-tion products. If both boron and fluorine are present in the glass, both volatilize from the surface of the molten glass of the streams and the major chemical species present in the environ-ment is boron fluoride from the reaction of the fluoride with l~90S71;

boric oxide vapor.
This reaction reduces the vapor pressure of the boric oxidein the environment and accelerates its vaporization from the glass surface. The greater the depletion of the glass surface of boron by volatilization, the greater the viscosity and surface tension of the glass surface enhancing the stability of the cones of glass. The beads of glass forming at the tips of the orificed projections during start-up tend to be longer and thinner reduc-ing the tendency for the beads to contact or hang up on the fin shields and cause flooding at the stream flow region of the feeder.
By reason of environmental restrictions, textile glass compositions are being used having little or no fluorine in the compositions. If only boron is present in the glass, with little or no fluorine, the major chemical species in the stream flow environment is boric oxide B2O3. The equilibrium vapor pressure is low at the feeder tip temperature so that volatilization from the glass very rapidly reaches equilibrium in the relatively quiescent or stagnant environment, and surface volatilization becomes very 9 low.
Hence, in the absence of a substance such as fluoride to reduce the vapor pressure of the gaseous boric oxide, the beads of glass formed at the tips of the orificed projections during start-up tend to be large in diameter and substantially shorter due to the lower viscosity and surface tension of the glass sur-face. The vapor pressure of the gaseous boric oxide decreases very rapidly with decreased temperature so that solid boric oxide B2O3 condenses on the fin shields or metal members resulting in a comparatively rapid build-up or boron compounds on the fin shields or metal members. The fibre-forming operation must be interrupted frequently to clean the fin shields.

lO9V57~

To overcome this a gaseous environment is provided between rows of depending projections on the stream feeder and above the metal members or fin shields, the environment being effective to ~liminate or greatly reduce the accumulation on the fin shields of solids from the volatiles emitted from the glass and promote the formation of longer and thinner beads of glass during start-up to thereby reduce the tendency of flooding of glass over the stream flow area of the feeder.
The method of producing the gaseous environment includes the supplying or delivery of streams of gas of low volume and at low velocities between rows of the depending projections and above the fin shields providing continuous movement of the gas between the rows of projections for eliminating the stagnant en-vironment at such regions, the gas effecting reactions with the volatiles emanating from the glass to attain the above-mentioned results of preventing fin shield build-up and modifying the con-figuration of the beads of glass formed dur~ing start-up.
As shown in Figure 1, 3 and 4, manifold means comprising manifolds 55 and 55' are respectively disposed at each side of the stream feeder 10. Welded or otherwise secured to the mani-fold 55 are tubes or nozzles 57 for delivering streams of gas from the manifold 55. As shown in Figures 2, 3 and 4, each tube or nozzle 57 is disposed above and in lenthwise parallel relation with the adjacent fin shield 48.
The streams of gas from the tubes or nozzles 57 are direct-ed above and lengthwise of the adjacent fin shields or metal mem-bers 48 and between transverse rows of orificed projections 18 de-pending from the feeder floor or tip section of the stream feeder 10 .
As shown in Figures 2, 3 and 4, each tube or nozzle 57' ~O9~S76 connected with the manifold 55' is disposed above and in length-wise parallel relation with the adjacent fin shield 48. The streams of gas from the tubes or nozzles 57' are directed above and lengthwise of the adjacent fin shields or metal members 48 and between transverse rows of orificed projections 18 depending from the feeder floor or tip section of the stream feeder 10.
As shown in Figures 3 and 4, the tubes or nozzles 57 and the tubes or nozzles 57' are in aligned relation transversely of the feeder so that the gas streams directed or delivered from the nozzles impinge one another. Through this arrangement the gas streams, moving between rows of projections and above and in lengthwise parallel relation with the fin shields or metal mem-bers 48, provide a continuously moving gaseous environment bet-ween rows of depending projections 18 thus obtaining a more uni-form reaction o the gas with the volatiles from the glass.
With reference to Figure 4, the manifold means 55 and 55' are joined by tee fittings 60 and 60'. The tee 60 is connected by tubular means with a valve or valve means 63, the valve 63 being connected by a pipe or tube 64 with the gas supply. The tee 60' is connected by tubular means with a valve or valve means 63', the valve 63' being connected by a pipe or tube 64' with the gas supply. The valves 63 and 63' regulate or control the flow of gas to the manifold means 55 and 55'.
It is found that a gas such as water vapor or steam at a temperature of above 250 F. or more provides a gas environment above the fin shields or metal members 48 and between rows of depending projections 18 on the stream feeder floor which is ef-fective to attain the chemical reactions with volatiles emitted from a glass having boron therein but little or no fluorine to greatly reduce or minimize the accumulation or build-up of solids lO9~ 7~

or condensation products on the fin shields or metal members 48 and to render the glass beads formed during start-up longer and thinner to reduce the tendency of flooding of the glass over the feeder floor or tip section.
If boron is present in the glass with little or no fluo-rine, the major chemical species in the environment is boric oxide. The water vapor or steam reacts with the boric oxide B2O3 as a gas to form a gas HBO2, meta-boric acid, but this is an equilibrium reaction with the amount of boric oxide as a gas converted to a gaseous meta-boric acid increasing as the square root of the water vapor or steam concentration.
The equilibrium vapor pressure of the gas HBO2 with HBO2 as a solid is several orders of magnitude greater than of the gas B2O3 with the solid B2O3. As the temperature is reduced the meta-boric acid HBO2 as a gas further reacts with the steam or water vapor to form H3BO3, ortho-boric acid in gas form which has a relatively high vapor pressure at all temperatures above 250 F.
Therefore, the H3BO3 remains in gas form in the environ-ment and eliminates or reduces the condensation of boric oxide on the metal members or fin shields 48 and promotes the formation of longer and thin beads of glass at the ends of the orificed pro-jections 18 during start-up.
The velocity of the water vapor or steam delivered from the nozzles 57 and 57' is comparatively low, the maximum velocity, being about 170 centimeters per second. The volume of steam or water vapor of the streams delivered from the nozzles 57 and 57' is comparatively low. As an example, with a stream feeder floor section or bushing having 816 orificed projections or tips, the 30 range of volume of water vapor or steam is from 500 to 3000 cubic las()s7tj centimeters per minute, or from .62 to 3.7 cubic centimeters per minute for each tip or projection.
The preferred volume of steam is 2.45 cubic centimeters per minute for each projection or tip, which is equivalent to 2000 cubic centimeters per minute for a stream feeder section or bushing having 816 orificed projections or tips.
Another gas that may be used as a gaseous environment above the fin shields 48 and between rows or orificed projections 18 to eliminate or minimize build-up of compounds on the fin shields or metal members and promote the formation of long thin beads of glass at start-up is a mixture of hydrogen fluoride and air in a ratio of one part hydrogen fluoride to about ten parts of air by volume.
The preferred flow rate of hydxogen fluoride in the air and hydrogen fluoride mixture is about .075 cubic centimeters per minute for each orificed projection or tip 18. With this gas the reaction between boric oxide B2O3 in gas form and hydrogen fluoride HF in gas form results in the formation of boron fluo--ride BF3 in gas form which remains in gas form and thus elimin-ates the deposition of boron compounds on the fin shields ormetal members 48 and promotes the formation of longer and thinner beads of glass at the orificed projections during start-up. The amount of hydrogen fluoride employed in the gaseous environment is well within the amount allowed by the present environmental restrictions.
Figure 5 illustrates schematically the configurations of glass forming at the exits of the orificed projections 18 during start-up operations. In the use of a glass composition contain-ing little or no fluorine and without the gas environment of the invention, the beads of glass illustrated at 68 in broken lines io90'j~7~

are short and of comparatively large diameters. This form of bead configuration promotes the tendency for the beads to contact one another and contact the metal members or fin shields causing the glaqs to flood across the underside of the floor of the stream feeder or bushing.
With the use of the gas environment of the invention above the fin shields and between rows of depending orificed projections, the beads formed of a glass composition having little or no fluo-rine are longer and of lesser diameter, such beads being indicat-ed at 70. Beads of the latter character drop freely with no ten-dency to contact or hang up on the fins and cause flooding of the feeder floor.
It is found that a further advantage results from the use of the gas environment of the invention. The cones of glass 22 at the exits of the orificed projections 18 during attenuating operations are shorter and more stable than cones of glass in the absence of the gas environment.
It is important that the metal members or fin shields 48 are operated at a temperature above the condensation temperature of the compounds or materials formed as a result of the addition of the gas. Otherwise those reaction products would have a ten-dency to accumulate on the fin shields. With the water vapor in-jection system, for example, the fin shields or metal members 48 should be operated above 250F.
Furthermore the gas is delivered above the level of the terminal of the depending projections and between rows of depend-ing projections and oriented also so as to not directly impinge the floor or tip section 16 of the feeder 10. Since the volume and velocity of the gas is so relatively low it is believed there is no significant increase in the amount of heat transferred from 109~7~

the feeder or the fibers being formed. Therefore, the electrical power consumed by the feeder by the fiber forming process will not be significantly increased. It is believed to be, at maxi-mum, less than a 1~ increase in the power consumed by the feeder 10 .
The use of the gas injection in forming glass fibers particularly from glass compositions containing little or no fluorine enables the fiber-forming operation to be c~ntinued without interruption for much longer periods of time before it becomes necessary to clean the fin shields.
It is apparent that, within the scope of the invention, modifications and different arrangements may be made other than as herein disclosed, and the present disclosure is illustrative merely, the invention comprehending all variations thereof.

Claims

The embodiments of the invention in which an ex-clusive property or privilege is defined are defined as follows:

1. A method of processing heat-softened glass com-prising flowing streams of the glass from rows of orifices in a stream feeder, attenuating the glass streams to fibres, con-ducting heat away from the glass streams through heat absorbing members adjacent the glass streams, conveying heat away from the heat absorbing members by a cooling fluid, and directing streams of gas above and in substantial parallelism with the heat absorb-ing members to react with a primary gas supplied by the streams of glass to form a secondary gas and maintaining the heat ab-sorbing members above the condensation temperature of the sec-ondary gas to reduce deposition of condensation products of volatiles from the glass streams on the heat absorbing members.

2. A method according to claim 1 wherein the streams of gas comprise steam.

3. The method according to claim 2 wherein said orifices are provided by orificed projections formed on said stream feeder and wherein the volume of steam delivered for each orificed projection is in a range of .62 cubic centimeters and 3.7 cubic centimeters per minute.

4. The method according to claim 2 or 3 wherein the velocity of the streams of steam is about one hundred and seventy centimeters per second.

5. A method according to claim 1 wherein said glass contains boron and the gas forming said streams of gas is selected from a group comprising steam or a mixture of air and hydrogen fluoride.

6. A method according to claim 5 wherein the gas forming said streams of gas comprises a mixture of hydrogen fluo-ride and air.

7. The method according to claim 6 wherein the mix-ture of hydrogen fluoride and air is in a ratio of about one part hydrogen fluoride to ten parts of air by volume.

8. The method according to claim 6 or 7 wherein said orifices are provided by orificed projections depending from said stream feeder and wherein the flow rate of the mixture of hydrogen fluoride and air delivered for each depending orificed projection of the stream feeder is about .81 cubic centimeters per minute.

9. A method of processing heat-softened glass com-prising flowing streams of glass from rows of orificed depending projections of a stream feeder, attenuating the glass streams to fibres, conducting heat away from the glass streams through metal members adjacent the rows of glass streams, and directing streams of gas from regions adjacent the sides of the stream feeder into impinging relation at zones between rows of the depending pro-jections to react with a primary gas supplied by streams of glass to form a secondary gas and maintaining the heat absorbing member above the condensation temperature of the secondary gas to reduce condensation of volatiles from the glass streams on the metal members .

10. A method according to claim 9 wherein said streams of gas are directed from regions adjacent the sides of the stream feeder lengthwise of and above the metal members into impinging relation.

11. Apparatus for processing fibre forming mineral materials comprising a stream feeder having a plurality of ori-fices therein for generating streams of material, heat absorbing members arrayed between and below said orifices and gas intro-ducing means for introducing gas above and adjacent said heat absorbing members to inhibit condensation of volatiles from the streams of mineral material on the heat absorbing members.

12. Apparatus for processing heat-softened glass including a stream feeder containing heat-softened glass, said feeder having transverse rows of depending projections, said projections having orifices to permit flow of streams of glass from the feeder, means for attenuating the streams of glass to fibres, a plurality of heat absorbing members arranged in side-by-side parallel relation, each of said members disposed between rows of glass streams flowing from the stream feeder, manifold means adjacent the stream feeder and a plurality of nozzles con-nected with the manifold means, each of said nozzles being disposed to direct a stream of gas above and in lengthwise rela-tion with the adjacent heat absorbing member.

13. Apparatus according to claim 12 including a tubular header supporting the heat absorbing members and acco-modating cooling fluid for conveying away heat from the members.

14. Apparatus according to claim 13 wherein said manifold means extends lengthwise of the stream feeder.

15. Apparatus according to claim 14 wherein said manifold means includes a manifold disposed adjacent each side of and extending lengthwise of the feeder, each having a plurality of nozzles connected thereto, the nozzles connected with one manifold being in respective alignment with the nozzles connected with the other manifold, the nozzles being disposed to direct streams of gas into impinging relation at regions above the heat absorbing members and between rows of the depending projections.

16. Apparatus according to claim 14 or 15 wherein the nozzles terminate adjacent the lengthwise edge regions of the stream feeder.

17. Apparatus according to claim 12, 13 or 15 where-in the exits of said nozzles are above the level of the terminals of the depending projections to direct streams of gas between rows of depending projections.

18. The method of processing molten glass compris-ing:
supplying streams of molten glass;
conducting heat away from the streams by a member adjacent the streams;
reacting a gaseous fluid with a primary gas supplied by the streams of glass to form a secondary gas; and, maintaining the temperature of said member above the condensation temperature of the secondary gas to reduce the ten-dency of the secondary gas to condense upon said member.

19. The method of claim 18 wherein the fluid reacts with the primary gas at a zone wherein the streams are attenuated into filaments.

20. The method of claim 19 wherein the glass con-tains boron but is substantially fluorine-free and the primary gas is boric oxide.

21. The method of claim 20 wherein the gaseous fluid is selected from the group consisting of steam and a mixture of hydrogen fluoride and air.

22. The method of claim 21 wherein the secondary gas is a gas selected from the group consisting of meta-boric acid, ortho-boric acid, and boron fluoride.

23. The method of processing heat-softened boron-containing glass comprising:
flowing streams of the glass from orifices arranged in rows on the floor of a stream feeder;
attenuating the glass streams to fibres;
conducting heat away from the glass streams through members adjacent the glass streams;
directing streams of gas reactable with boron-con-taining volatiles adjacent the heat-conducting members;
reacting the gas of the streams with boron-containing volatiles from the glass resulting in a gaseous boron compound;
and, maintaining the temperature of the heat-conducting members above the condensation temperature of the gaseous boron compound to substantially eliminate condensation of the compound on the members.

24. The method of claim 23 wherein the heat con-ducting members are in substantially parallel relationship with the feeder floor and said gas streams are directed in lengthwise relationship with said heat conducting members.

25. A method according to claim 23 wherein said heat conducting members are metal fin shields arranged in paral-lel relation with the feeder floor and between the rows of glass streams, and said streams of gas are directed between the rows of orifices, in parallelism with the feeder floor and above the fin shields.

26. The method according to claim 23, 24 or 25 wherein the gas of the streams is selected from a group compris-ing steam or a mixture of air and hydrogen fluoride.

27. The method of claim 23 wherein said gas is steam.

28. The method according to claim 23 wherein said orifices are provided by orificed projections formed on said stream feeder and wherein the volume of steam delivered for each orificed projection of the stream feeder is in a range of .62 cubic centimeters and 3.7 cubic centimeters per minute.

29. The method according to claim 27 or 28 wherein the velocity of the streams of steam is about one hundred and seventy centimeters per second.

30. The method of claim 23 wherein said gas is a mixture of hydrogen fluoride and air.

31. The method according to claim 30 wherein the mixture of hydrogen fluoride and air is in a ratio of about one part hydrogen fluoride to ten parts of air by volume.

32. The method according to claim 30 or 31 wherein said orifices are provided by orificed projections formed on said stream feeder and wherein the volume of the mixture of hydrogen fluoride and air delivered for each depending orificed projection of the stream feeder is about .81 cubic centimeters per minute.

33. A method of processing molten glass comprising:
attenuating streams of the glass into filaments at a first zone;
conducting heat away from the streams by a member adjacent the streams at the first zone;
directing a first gas into the first zone in a re-actable relationship with a second gas supplied to the first zone by the streams of glass to form a third gas; and, maintaining the temperature of said member above the condensation temperature of the third gas to reduce the tendency of the second gas and third gas to condense upon said member.

34. The method of claim 33 wherein the glass con-tains boron but is substantially fluorine-free and the second gas is boric-oxide.

35. The method of claim 34 wherein the first gas is a gas selected from the group consisting of steam and a mixture of hydrogen fluoride and air.

36. The method of claim 34 or 35 wherein the third gas is a gas selected from the group consisting of meta-boric acid, ortho-boric acid, and boron fluoride.