coating on glass mosaic
02-23-2012, 11:28 AM,
coating on glass mosaic
We have small sized glass mosaic which are transparent, one surface is flat and the other one have few designs of lines. now we want to make the designed surface opaque, i.e. we want to apply some colour on the designing surface so that when we see it from the other side it looks asthetic. we done arc spray coating of two dissimilar metal wires on these mosaics and found that few of these stick to the surface and our purpose seemed completed.

but now problem is due to mass production requirements idea of applying coating on small prepared glass pieces is not worthwhile so we are planning to install equipment in between its production, where these glass pieces are in the form of a regular sheet, and temperature of that sheet where we want to do coating is around 800-900 degree centigrades. photographs of this sheet during the production is attached. now question comes is will any coating stick to this glass? and once the glass sheet is cooled down what may happen to coating? material we tried were - Copper-Phosphorus bronze, Copper-brass, Copper, SS, Aluminium etc.

if any buddy having similar kind of experience please give us your suggestion.

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02-23-2012, 03:53 PM,
RE: coating on glass mosaic
Hi Jaydev

I think you need to try this. I know that some coatings that we had trouble with adhering to glass sprayed cold were overcome by heating glass to these sorts of temperature. I think it certainly worth experimenting with and suggest you keep coating thickness to a minimum.
02-24-2012, 09:21 PM,
RE: coating on glass mosaic
If you are going to try again. I would suggest very soft metals like zinc or tin.
02-25-2012, 05:15 AM,
RE: coating on glass mosaic
(02-24-2012, 09:21 PM)kschewe Wrote: If you are going to try again. I would suggest very soft metals like zinc or tin.

Thanks for the reply sir, but metal like zinc is not worthwhile to try, because its colour is dirty which will not solve our actual purpose of giving the glass a good asthetic colour! and also at higher temperatures i.e. 800-900 degree centrigrades only metals with higher melting point can stick.

02-26-2012, 12:12 AM,
RE: coating on glass mosaic
I did an experiment once, where i grit blasted glass, to roughen up the surface. I was able to only get very soft metals to stick. I would try again with a flame spray wire gun and try babbit. Tin stick very well. It can maybe be used as a bond coat.
02-28-2012, 04:49 AM,
RE: coating on glass mosaic
(02-26-2012, 12:12 AM)kschewe Wrote: I did an experiment once, where i grit blasted glass, to roughen up the surface. I was able to only get very soft metals to stick. I would try again with a flame spray wire gun and try babbit. Tin stick very well. It can maybe be used as a bond coat.

Glass at 800 degrees don't require any blasting before coating, & in our case where we want to apply some beautiful colours on the surface which must look good from the other side of the glass can not be grit blasted as this will make the surface dirty
03-01-2012, 07:07 PM, (This post was last modified: 03-01-2012, 07:13 PM by MichiganMan.)
RE: coating on glass mosaic
I couldn't resist getting in on this one. Presumably at 800-900C the "glass" is somewhat plastic (probably using these kind of temps in forming operations for the glass), and the material sprayed into it is embedding into the surface rather than conforming to surface profile. I would try alloys with the desired aesthetics, high melting point and try to find a material with as close a coefficient of thermal expansion to the glass as possible. I don't know what 'look' you are going for in terms of color, but the high melting point should help the metal retain is adhesion once embedded into the glass. I would expect a lower melting point material to liquefy and flow if the temperature is maintained long enough which would most likely cause it to delaminate after cooling. I suspect that thin coating as Gordon suggests above would minimize the tension affect pulling away from the surface as well. No more than a few thoudandths if even that thick. It will likely take some trial and error to find the best solution.
If you continue to have difficult I might try a higher velocity (HVOF or even Cold Spray) process to increase depth of penetration and reduce coating tension to see if that helps.

As an afterthought, perhaps it would be worthwhile to use a wire that generates a thermite reaction when sprayed. The tiny pockets of intense heat from the thermite may be hot enough to fuse with the glass that it directly contacts and create a diffusion boundary in the coating. That would be pretty cool to see, and would probably solve the adhesion issue.
03-02-2012, 01:57 AM,
RE: coating on glass mosaic
Dear All,
Came across this article on above subject:
Liquid Flame Spraying for Glass Coloring
K.A. Gross, J. Tikkanen, J. Keskinen, V. Pitkänen, M. Eerola, R. Siikamaki, and M. Rajala
JTTEE5 8:583-589
The liquid flame spraying process has been developed to uniformly color hot glass objects. A solution
consisting of a metal nitrate dissolved in alcohol or water is fed to an oxyfuel torch and atomized in the
flame. The liquid evaporates from the droplet, and subsequent reactions produce metals or metallic oxides
that impact the hot glass surface. Flame spraying of Co, Cu, and Ag solutions onto soda-lime silica
glass at 900 to 1000 °C have produced blue, blue-green, and yellow colors. Typical spraying times are 5 to
20 s. Other colors have been produced by using a combination of transition metal ions. This method has
found application in studio production and in volume manufacturing of glassware.

Thank you
03-13-2012, 12:24 AM,
RE: coating on glass mosaic
Flame spraying was a very innovative application many years ago, in the production of windows double glazing, I settled the coating for many glass industries, the application was made heating the glass up to 700°c and then spraying copper with flame wire gun, after this two glasses were soldered, in order to form the double glass hollow, now this technology is obsolete, so you can spray copper, or copper alloys without problems, and the adhesion is very high, without any problem whe glass col or is heated again
Best regards

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