Method for producing a metal matrix for mosaic structures

A method for producing a metal matrix (32) which binds inclusions (12,15) in a stable structure (31) so that the surface areas of two opposing sides of each inclusion (12,15) are visible, thus enabling translucency. This method comprises the steps of securing inclusions (12,15) to a temporary backing (38) so that there are intervals (14) between the inclusions (12,15), depositing a metal fiber substrate (42) into the intervals (14) between the inclusions (12,15), and then melting a metal infiltrate (46) so that the infiltrate (46) coats the individual fibers and fills the spaces between the fibers. Upon cooling, the amalgam (48) of substrate (42) and infiltrate (46) thus formed constitutes the matrix (32) and border (34) of the structure (31). The inclusions (12,15) may be glass, marble, clay, metal, or other materials; the metal fiber substrate (42) is preferably fine bronze fiber and the infiltrate (46) is preferably conventional solder. The matrix (32) produced is flangeless which makes this method particularly suitable for producing translucent mosaic structures or, viewed alternatively, stained glass structures utilizing very small pieces of glass. The metal fiber substrate (42) and its method of deposition make this matrix (32) both cost-effective and stable over other methods which might be adapted to yield similar structures.

BACKGROUND - FIELD OF INVENTION 
This invention relates to the field of structures consisting of elements 
bound together by a metal matrix and more specifically to the fields of 
mosaic craft and stained glass craft 
BACKGROUND - DESCRIPTION OF PRIOR ART 
Traditional mosaic craft teaches a method of embedding small pieces or 
inclusions of glass or marble in a matrix of mortar or cement. These 
inclusions are typically small and roughly cube-shaped. As shown in FIG. 
1, the mortar matrix 13 covers the back side of each inclusion 12 and 
fills the intervals 14 between inclusions so that only one surface, the 
front surface, of each inclusion is visible. 
The value of a mosaic structure is in the overall pattern that these 
surface areas present to the viewer. A significant advantage of the mortar 
matrix is that it does not obscure any portion of the front surface. Thus, 
it enables the use of inclusions which are quite small. 
Suppose, however, that one desires to build a mosaic structure where both 
the front and back of each inclusion is visible and exposed. One reason 
for doing so might be to allow transparency. If this case, mortar may be 
present only in the intervals between the inclusions--when this is so, the 
amount of mortar present is not sufficient to support the overall 
structure under normal conditions and the structure as a whole will easily 
disintegrate. 
The two traditional methods of building stained glass structures are 
commonly known as the lead came method and the copper foil method. As 
shown in FIG. 2, the lead came method requires that the matrix 16 filling 
the intervals 14 between the individual inclusions of glass 12 consist of 
preformed lead strips called came. These are shaped in cross-section like 
the letter H. 
As shown in FIG. 3, the copper foil method requires that the edges of each 
inclusion of glass 12 be wrapped with copper foil 18 slightly wider than 
the thickness of the glass and that the excess be pressed flat against the 
front and back surfaces of the piece. The wrapped inclusions of glass are 
placed adjacent to one another and a solder bead 20 is formed along those 
parts of the foil which have been pressed against the surface. This forms 
an amalgam of copper and solder which also fills any intervals 14 between 
the inclusions. This amalgam is the matrix 22 of the copper foil 
structure. 
The matrices of the lead came and copper foil methods are structurally very 
similar and they have the advantage of: 
(a) enabling structures where a portion of both the front side and back 
side of each inclusion are visible, and 
(b) relative strength. 
As a result, they enable stable, translucent structures. 
These matrices share the disadvantage that, unlike mortar, they do not 
easily allow the use of small, mosaic-sized inclusions. Consider the 
following: 
The goals and values of traditional stained glass craft are realized with 
inclusions of glass which typically have a surface area ranging in size 
from 5 cm. sq. to 500 cm. sq. In contrast, the goals and values of mosaic 
craft are achieved with inclusions of glass or marble which have much 
smaller surface areas; typically, the surface area is in the range of 5 
mm. sq. to 25 mm. sq. Another way of looking at this is that a typical 
inclusion of glass in a classical mosaic has a surface area approximately 
100-1000 times smaller than a typical stained glass inclusion. 
Two significant problems emerge when the matrices of the lead came and 
copper foil methods are employed to bind such small inclusions: 
First is that the ratio of visible inclusion surface area to obscured 
surface area decreases dramatically. As shown in FIG. 4, both matrices 
have a heart 24 and a flange 26 which is of relatively invariant size. 
This flange obscures a portion 28 of the surface area of the inclusion 12. 
When this obscured portion 28 remains relatively constant and the overall 
size of the inclusion drops by a factor of 100-1000, the ratio of obscured 
surface area 28 to visible surface area 30 increases dramatically. A side 
effect is that any enabled translucency is severely diminished. 
Second is that of direct labor cost. These matrices are labor intensive and 
the amount of labor required to produce a structure of a given size is 
proportional to the total linear amount of matrix required to surround the 
inclusions. The linear amount of matrix is, in turn, proportional to the 
size and number of pieces required to complete the structure. In effect, a 
structure of mosaic-sized inclusions produced by the lead came or copper 
foil methods might require well over 100 times the labor required for a 
traditional stained glass structure of the same size 
Although the traditional methods of mosaic craft and stained glass craft 
fail to meet the goal of a matrix which binds mosaic size inclusions so 
that opposing sides are visible, and the visible surface area of the 
inclusions is much greater than the obscured area of the inclusions, and 
the matrix is structurally sound, there are two other solutions which are 
worth examining. 
H. F. Belcher describes a method (U.S. Pat. Nos. 303,359 (1884); 317,077 
(1885); 396,911 (1889); 396,912 (1889)) for producing a matrix which 
appears to have several advantages: 
(a) The matrix enables two opposing surfaces of each inclusion to be 
visible, 
(b) The matrix is potentially flangeless and hence can allow a high ratio 
of visible surface area to obscured surface area regardless of the size of 
the inclusion, 
(c) The matrix is reasonably strong and enables a stable structure, 
(d) The direct labor cost of Belcher's matrix is relatively independent of 
the number and size of inclusions in the structure. Thus, unlike the lead 
came and copper foil methods, the direct labor cost is not significantly 
increased by the use of mosaic size inclusions. 
I would argue, however, that the direct labor cost of his method was 
invariably high, albeit independent of inclusion size. This is because 
formation of his matrix apparently required several skilled workmen 
working in concert over a long period of time. Further disadvantages of 
Belcher's matrix are that it: 
(a) requires significant capital investment in furnaces, vestments, cranes, 
etc. 
(b) requires materials, e.g., asbestos, and practices which would be today 
considered unsafe and detrimental to the health of the producers. 
DelGrande describes a method (U.S. Pat. Nos. 4,172,547 (1979); 4,252,847 
(1981); 4,255,475 (1981)) which requires the application of a silicone or 
firebrick adhesive to each edge of each inclusion within a structure. 
While the adhesive is still tacky, copper powder is sprinkled onto the 
adhesive. When the pieces are placed adjacent to one another, the layer of 
copper serves as a substrate which will adhere to molten solder. The 
combination of adhesive and copper-solder amalgam form the matrix of the 
structure. 
DelGrande's method appears at first glance to share advantages a-c of 
Belcher's listed above. Further, his method is much less costly in terms 
of capital equipment expense than Belcher's and does not appear to involve 
unsafe materials and practices. However, DelGrande's method has some 
serious disadvantages. Although he states otherwise, his method requires 
substantially the same direct labor cost as the traditional copper foil 
method: consider that each edge of each inclusion must be coated with 
adhesive. This is very similar to the requirement that each edge of each 
inclusion be wrapped with copper foil. Note that the adhesive must be 
carefully and laboriously applied to the edges of each inclusion or it 
will coat and obscure its surface. And the labor cost of creating the 
copper-solder amalgam of his matrix is substantially the same as that 
required by the copper foil method. Thus the total labor cost for 
producing a structure with his matrix is dependent on the number and sizes 
of pieces in the structure. This cost is prohibitive when mosaic size 
inclusions are utilized. 
A further disadvantage of DelGrande's method is that it requires that the 
adhesive he uses remain a permanent part of his matrix. Although he states 
otherwise, the adhesive is in fact not very permanent and this leads to a 
major disadvantage: under normal environmental conditions, the adhesive 
will degrade far more rapidly than the copper solder amalgam which 
composes the remainder of the matrix. When the matrix is flangeless and 
non-obscuring and the "permanent" adhesive degrades, the inclusions of 
glass will separate from his matrix and the structure will fail 
prematurely. 
SUMMARY OF THE INVENTION 
Accordingly, several objects and advantages of this invention are to 
provide a metal matrix binding inclusions in a stable structure so that: 
(a) The matrix allows two opposing surface areas, the front and the back, 
of each inclusion to be visible. This in turn allows inclusions to be 
translucent when translucency is desirable. 
(b) The matrix is flangeless. This characteristic allows entire surface 
visibility, front and back, of each inclusion even when the inclusion is 
mosaic size. 
(c) The matrix is strong and stable. 
(d) Production of the matrix does not require unsafe materials or 
practices. 
(e) The matrix requires minimum capital equipment outlay. 
(f) The direct labor cost of the matrix is minimized. 
(g) The matrix does not degrade prematurely under normal environmental 
conditions. 
These and further objects and advantages of my invention are accomplished 
by the following steps: 
Using a temporary adhesive, one secures inclusions to a temporary backing 
in a desirable pattern so that there are intervals between the inclusions. 
Then one deposits a metal fiber substrate into the intervals between the 
inclusions so that the intervals are substantially filled. Any excess 
fiber outside the intervals is removed. Then one coats the metal fibers 
with a fluxing agent. Then one melts a metal infiltrate so that the 
infiltrate coats the individual fibers of the substrate and fills the 
spaces between the fibers. Upon cooling, the amalgam of substrate and 
infiltrate thus formed constitutes the matrix and border of the structure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A representative mosaic structure 31 constructed in accordance with the 
methods of this invention is shown in FIG. 5. A set of glass inclusions 
12, and bronze inclusions 15, are surrounded and bound by a continuous 
metal matrix 32. The glass inclusions 12 represent the class of 
conventionally unsolderable materials and also the class of translucent 
materials. The bronze inclusions 15 represent the class of conventionally 
solderable materials. The structure has an edging or border 34 which is 
continuous with the matrix 32. 
The method for constructing the matrix and border is shown sequentially in 
FIGS. 6-11. As shown by FIG. 6, a set of inclusions 12 is joined by a 
temporary layer of adhesive (not shown) to a stiff temporary backing 38 at 
intervals 14. Border pieces 40 are also joined by the adhesive to the 
backing at an interval 14 around the edges of the set of inclusions 12 and 
the adhesive is allowed to dry completely. 
The inclusions are preferably squareish, have front and back surfaces which 
roughly form parallel planes, are made of stained glass, are approximately 
3.2 mm. thick, and have a surface area in the approximate range of 5 mm. 
sq. to 25 mm. sq. It is likely that they could be of almost any shape as 
long as each has one roughly flat surface which can be securely glued to 
the backing. Although it is likely that the surface areas may be of almost 
any size, this method achieves maximum cost-effectiveness when the surface 
areas are my preferred size. It is likely that the inclusions may be 
composed of almost any material including conventionally unsolderable 
materials such as glass, marble, clay, iron, etc. or conventionally 
solderable materials such as lead, tin, copper, brass, bronze, zinc, etc., 
or combinations of these metals, as long as: 
1) the material is not altered in an undesirable way by temporary heat of 
approximately 371-427 degrees C. and, 
2) the material remains bonded to the temporary adhesive and backing when 
subjected to this temporary heat. 
The adhesive is preferably fish glue (as sold by Norland Products, Inc., 
New Brunswick, N.J.). Other heat resistant adhesives may be used but note 
that the adhesive is a temporary device and not part of the final 
structure. Its ease of removal is a factor. 
The stiff temporary backing is preferably a flat sheet of plywood with a 
coat of varnish. It is likely that this backing could be composed of a 
variety of materials as long as the backing is stiff, somewhat heat 
resistant, somewhat moisture resistant, and bonds securely to the 
adhesive. A degree of stiffness is necessary to counteract the effects of 
uneven heating which occur subsequently in this method. It is likely that 
the backing could be other than flat, e.g., a gentle curve, like those in 
Tiffany lamps. 
The border pieces are preferably brass, round, and 2.4 mm. in diameter. It 
is likely that they could be of any cross-sectional shape. It is likely 
that they could be of any diameter roughly approximate to the thickness of 
adjacent inclusions. It is likely that they could be composed of almost 
any material which meets the same conditions as for inclusions: 
1) the material is not altered in an undesirable way by temporary heat of 
approximately 371-427 degrees C. and, 
2) the material remains bonded to the temporary adhesive and backing when 
subjected to this temporary heat. 
The border pieces are a part of the final structure in my preferred 
embodiment but they are not a necessary part of the final structure in all 
embodiments. 
The size of the interval between the inclusions is preferably 1-2 mm. It is 
likely that interval sizes larger than this range are possible. It is 
likely that interval sizes smaller than this range may be possible under 
conditions mentioned later. 
As shown by FIG. 7, a quantity of metal fiber 42, the substrate of the 
matrix, is placed in the intervals 14 between the inclusions 12 and 
between the inclusions 12 and the border pieces 40 so that the intervals 
14 are substantially filled. The metal fiber 42 represents both 
conventionally solderable metal fibers and conventionally unsolderable 
metal fibers. The primary function of the border pieces 40 is to help hold 
the fiber 42 in place. 
The substrate is preferably grade fine bronze fiber also known as fine 
bronze chopped wool, as sold by International Steel Wool Corp., 
Springfield, Ohio. The strands of this fiber are reportedly 0.03-0.06 mm. 
in diameter and reportedly have a nominal length of 6.35 mm. It is likely 
that metal fiber made in other grades could work. It is likely that grades 
larger than fine might work well with intervals substantially larger than 
my preferred range of 1-2 mm. wide and 3.2 mm. deep. It is likely that 
grades smaller than fine would work with my preferred intervals of 1-2 mm. 
and such finer grades might even enable smaller intervals; however, such 
finer grades are apparently not commercially available. It is likely that 
the fiber may be made of materials other than bronze. Fiber made of a 
conventionally solderable metal other than bronze is an obvious 
possibility. Fiber made of conventionally unsolderable metals might work 
under some circumstances. In general, the choice of substrate material is 
codetermined by the choice of infiltrate material, flux, and the amount of 
heat required to form substrate and infiltrate into a stable amalgam. 
Those choices may impact the choices of adhesive and backing material. 
My preferred method of placing the metal fiber substrate in the intervals 
utilizes a container with a removable lid. This lid has holes drilled in 
it of approximately 4 mm. diameter. This lid is removed, the container is 
partially filled with the fiber substrate and the lid is secured. The 
container is shaken like a salt shaker over the intervals so that the 
fibers separate and fall through the holes in the lid and into the 
intervals. After the intervals are filled, any excess fiber which has 
fallen onto the glass surfaces is removed. Note that it is this method of 
placing the substrate in the intervals which enables my method to achieve 
cost effectiveness over DelGrande's method of coating the edges of each 
inclusion with adhesive and then coating the adhesive with metal 
particles. It is likely that other methods of placing the substrate in the 
intervals might work as long as such methods loosen the individual fibers 
and allow them to resettle and recompact into the intervals. 
As shown in FIG. 8, a fluxing agent 43 is then applied to the metal fiber 
substrate 42. 
My preferred agent is oleic acid mixed with alcohol in a proportion of 3.5 
parts oleic acid by volume to 1 part alcohol by volume. My preferred 
method of application is to spray this mixture using a spray bottle. It's 
likely that other flux mixtures and fluxes and methods of application 
could work. 
As represented by FIG. 9, a heated plate 44 and a molten metal infiltrate 
46 are brought into proximity to the substrate 42 and flux 43. The molten 
metal infiltrate 46 represents both conventional, i.e., tin-based, solders 
and unconventional solders. Upon touching the substrate and flux, the 
molten infiltrate coats the individual fibers of the substrate and fills 
any spaces between the fibers. Note that the backing 38 should be level at 
the point of contact between substrate and infiltrate. The quantity of 
infiltrate 46 used should be sufficient to substantially fill all 
intervals to the surface of at least one of the inclusions surrounding 
each interval. The infiltrate is allowed to cool and solidify. 
The heated plate is preferably a Weller 371 degree C. or a Weller 427 
degree C. soldering tip fitted to a Weller W100 temperature-controlled 
soldering iron as available from CooperTools, Apex, N.C. However, many 
soldering iron/tip combinations would function equally well with my 
preferred substrate/infiltrate choices as long as the tip temperature is 
held steady in the 371-427 degree C. range. The process will partially 
function at a somewhat lower temperature, e.g., 315.6 degrees C., but not 
as well. Temperatures higher than 427 degrees C. might work but could 
prove overly destructive to the temporary glue bonds which hold the 
inclusions in place. 
It is likely that the heated plate could be other than a soldering iron 
tip. One possibility is a plate with a cast-in heating element which can 
be maintained at a stable temperature of 371-427 degrees C. If such a 
plate were larger than a typical soldering iron tip, it might reduce labor 
time. However, use of such a plate might also lead to diminished matrix 
quality. 
My preferred infiltrate is 60/40 tin/lead solder in solid core wire form. 
It is likely that other conventional, i.e., tin-based, solders, including 
lead-free can also produce satisfactory results. Note that lead-free 
solders may require use of a fluxing agent other that my preference. 
Lead-free 95/5 tin/antimony, for example, works better with a petroleum 
jelly/zinc chloride/ammonium chloride flux such as Oatey no. 5 lead-free 
flux than it does with oleic acid. The choice of an metal infiltrate other 
than conventional solder might work if it forms a stable amalgam with a 
chosen substrate which is a metal fiber of conventionally unsolderable 
material. 
As represented by FIG. 10, upon cooling, the metal fiber substrate and the 
infiltrate form an amalgam 48. This amalgam is in fact the matrix 32 and 
border 34 of this invention. When my preference of border pieces 40 is 
used, they are incorporated into the amalgam of the border 34. The 
structure is pried or lifted from the backing 38 and any adhesive or 
fluxing agent adhering to the inclusions, matrix, or border is removed. 
Water suffices to remove fish glue. Several agents, including mineral 
spirits, remove oleic acid. 
FIG. 11 shows the final result. It is a section view of FIG. 5 along the 
line 11--11. It displays the inclusions 12, the matrix 32, the border 34, 
and the border pieces 40. 
The reader will see that this invention provides a metal matrix binding 
inclusions in a structure in such a way that, 
a) the matrix allows two opposing sides of each inclusion to be visible. 
This enables translucency in the inclusions and in the structure as a 
whole. 
b) The matrix is strong and durable. The use of metal fiber as an integral 
component of the matrix gives it a strength and rigidity which may well be 
greater than that of matrices composed solely of infiltrate as is 
Belcher's. The matrix, unlike DelGrande's, avoids the incorporation of 
materials which would compromise its structural integrity. 
c) the matrix is flangeless. This allows maximum visibility of the surface 
areas of the inclusion when viewing the structure from front or back. It 
allows translucency when using small inclusions. 
d) the matrix is cost-conscious and cost-effective in comparison with the 
matrix of other methods which strive for the same objectives. It requires 
far less capital outlay than Belcher's method and considerably less direct 
labor time than DelGrande's matrix. 
e) The matrix does not require the use of unsafe materials or practices for 
its production as does Belcher's. 
The reader will also see that the structures produced by this invention 
might well have use as windows or lamps or free-standing screens or 
sculptures exposed to ambient or artificial light. Indeed, one might say 
that this invention enables core values from the fields of stained glass 
and mosaic to be embodied in a single structure. However, both the 
specifics of my description above and the overall spirit of this 
invention, i.e., that inclusions, metal fiber substrate, flux, metal 
infiltrate, heat, temporary adhesive, and temporary backing interact to 
form a unified structure where opposing surfaces of the inclusions are 
visible and unobscured, give this invention a broad range of applications. 
Accordingly, the scope of this invention should be determined by the 
appended claims instead of examples given.