Mr. Keth,
I work at a grocery store and sell my dags on ebay for quite a lot of money.
Mr. Keth,
I work at a grocery store and sell my dags on ebay for quite a lot of money.
Jason, if you want to try again, the traditional way to get noble metals to stick to glass is to first coat it with a thin layer of chromium. I have only ever done this with vacuum deposition, but there are certainly wet-chemical techniques too.
Thank you Struan, I will look into that. At some point of time I will also try vacuum as it seems more promising.
A couple more thoughts.
You only need a very thin layer of chromium: 100 Å is enough to keep a gold film attached to glass while subjected to all manner of chemical and thermal indignities. Some small amount of chromium can migrate to the surface of the overlayer through grain boundaries, but probably not enough to upset your chemistry.
Another option would be indium-tin-oxide (ITO) coated glass. ITO is a transparent, conductive oxide and although I can't promise 100% that silver will work, most metals adhere much better to ITO than to bare glass. You can buy expensive glass sheets ready-coated with ITO for technical use or for making flat panel displays, but it is also widely available as heat reflective glazing, so a good glass merchant or a company that makes windows and patio doors can also supply it.
Mind you, I think the example you posted is a fantastic argument for poor adhesion.
Struan, I had been told by an amateur telescope maker that I should apply tin oxide (or perhaps ITO?) to my glass before the silver, but never found instructions how to do so at home. So, I will look into applying chromium or buying ITO glass. Thanks!
One more project, sigh...
Jason, ordinary jeweler's rouge (commonly used by amateur telescope makers in the polishing of their glass) is nothing more than tin oxide (though many modern workers use cerium oxide instead); burnishing the glass with tin oxide rouge as a near-final step before silvering might well leave enough of the oxide on the glass to improve adhesion.
Also, of course, the glass needs to be chemically clean (aside from any intentional coating) prior to silvering; the usual process for cleaning glass for a silver telescope mirror coating intended to be "permanent" (as in, lasting six months to a couple years before it needs recoating) involves washing with nitric acid, burnishing with rouge on wads of wet cotton, and using 91% isopropyl or ethyl alcohol or technical grade acetone to ensure spot-free drying from the final rinse.
However, telescope mirrors aren't habitually subjected to a gilding torch -- I'd forgotten about that part of the process when I originally suggested use of silvered glass for Daguerreotypy. I'd guess you'd want to use Pyrex or other low-expansion glass instead of ordinary soda-lime window glass, to avoid cracking the plate when you gild (which, BTW, is the missing step I couldn't recall that sinters the developed silver grains from the sensitive fumed coating onto the base silver). I honestly don't know if you can get the silver hot enough on common glass to sinter/gild without breaking the glass. If all else fails, I believe Schott Glass sells Pyrex or similar borosilicate in float glass form (flat panes similar to window glass).
If a contact print at arm's length is too small to see, you need a bigger camera. :D
Donald,
I used cerium oxide to clean the glass, but will try rouge next time. Other than that, I pretty much followed your suggestions. I clean the plate with soap and water, then scrubbed with cerium oxide and soaked to plate in nitric acid. I never dried the plate between preparation and silvering, just kept it in a dilute bath of the acid and then gave it a quick rinse in distilled water before it went into the dextrose bath.
I haven't yet bothered with pyrex glass; it is pretty expensive and I would have to special order it as I can't easily get it where I live. In any case, I will certainly take all of your suggestions to heart when I try again.
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