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artfem
Administrator
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Thu Mar 13th, 2008 05:40 pm |
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bbates:
Don't apologize for beating a dead horse, it is something I pride myself in. Its the beating of the live horses we should disdain.
Your comments illustrate the issue that has been discussed previously; we can misunderstand or mis-explain events when we rely solely on empirical evidence. It is understandable that visual artists think they must see it for it to be true, but often the most unreliable witnesses in court cases are the eyewitnesses. We all see the world from our own experience/vantage point. This makes our view of relaity subjective rather than objective. The viewed experience may a good place to start when attempting to define the physical world, but it must be supported by real science .
The concept of the "battery" and subsequent corrosion of zinc is not a theory or an idea, it is scientific fact. Galvanic corrosion ocurrs when dissimiliar metals are placed into an electrolyte. The rate of corrosion is a function of how far apart the metals are on the galvanic scale and the strength of the electorlyte. That you have not seen the results of this phenomenon simply means all of the necessary elements were not present. The missing element in the cases you discuss is probably the electrolyte. The electrolyte is necessary for the transport of charged metal ions to travel form the zinc to the lead. Simple moisture is typically insuffcient to act as an electrolyte.
Toaddress your questions:
A. Could the environment have something to do with the corrosion, midwest vs. coastal areas? Perhaps the air has more corrosive elements on the coasts.
Yes, but probably not in the way you think. The coastal environment is more likely to carry salt in the air and the water borne mist than in the midwest. The salt dissolves in the moisture and condenses on the zinc lead connection. The dissolved salt forms an electrolyte and allows for the ion transfer that results in the corrosion.
B. We almost never put in windows without stormglazing or insulated units in front of them to prtect from the elements. Does this "corrosion problem" still applu to these windows not directly exposed to outside air?
Ironically, depending on the exact setting details, this type of installation can often intensify the corrosion effect due to increased condensation in the inter stitial space if it is not properly vented. Further, stained glass windows do not need to be protected from the elements. There are rare cases wherein paint or glass instability requires that the window be separated from the elements (primarily standing water) but other than this, there should be no problems with modern glass, especially if it is not painted.
C. We feel some windows NEED the extra rigidity for transporting and install. Would H zinc be any better than U zinc? The U is one layer hollow and the H is double layered folded all the way through, so...
I have transported window panels that far exceed what is recommended (not our design, window was being restored) such as 4' x 8' without need for extra rigidity at the perimeter. That being said, if you are more comfortable with the added rigidity, that is fine. The primary reason I have trouble with adding zinc to the perimeter is that many mistake this added rigidity for increased strength of the panel, and forego the application of a proper support bar system. While it may assist in transportation, once installed, the rigidity of the perimeter has no bearing on the strength of the panel or its installation. The issue of H or U zinc has no real bearing on the result.
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bbates
Non AGG Members
| Joined: | Fri Sep 28th, 2007 |
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| Posts: | 46 |
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Posted: Thu Mar 13th, 2008 11:26 pm |
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Thank you so much for that wonderful explanation.
With Zinc on the border... I find the rigidity (especially with large or long panels) to be very beneficial, especially with turning a window over or moving it around the shop. Yes, once the bars are connected, the zinc vs. lead does become more moot, I can totally understand that point. But, these are probably more personal preferences, not based on right or wrong.
As far as stormplating or a unit seperating the window from the elements, I think there are many issues at play, not just aging and corrosion issues. In the house we bought, there where windows in the front room with panes of stained glass in it and every winter we find sheets of ice forming on the inside of these pieces of glass. The room wasn't insulated the best, but there was a heater vent directly below the window. So if I understand what you are saying, as far as stormplating is concerned; may it have a greater impact on the hvac environment in the church rather than protection of the windows? Of course that is assuming the windows are vented properly.
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Hallie Monroe
AGG member
| Joined: | Thu Jan 17th, 2008 |
| Location: | New York USA |
| Posts: | 18 |
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Thu Apr 3rd, 2008 11:07 pm |
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Here is another example of why you may not want to use patina.
Or paint for someone elses design, glass choices or allow someone elses to put it together. This was a freelance job that was all of the above it. and was out of my control. All I did was paint high fire pigments. It looked as good as a sows ear could when it left my studio. The designer was thrilled the person who picked the glass and put it together was not experienced and used patina on the solder. I offered to repaint it but he chose not to. He used more patina to remove more of the matt so the spots no longer showed.
Did I mention that all I did was paint following the designers art. I'm glad I did not sign anything. I am sad that this will probably be in the church for years.Attached Image (viewed 16 times):
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