... glass is always a little bit liquid. Very old windows are slightly wider at the bottom than the top because the glass continues to flow over the years...
Karon, this is an old urban legend. Glass does not flow at all ! Look f..i. at http://www.glassnotes.com/WindowPanes.html Ciao. Gian ----Messaggio originale---- Da: [email protected] Data: 05/08/2011 1.51 A: "John Carmichael"<[email protected]>, <[email protected]> Ogg: RE: mock stained glass sundial v\:* {behavior:url(#default#VML);} o\:* {behavior:url(#default#VML);} w\:* {behavior:url(#default#VML);} .shape {behavior:url(#default#VML);}v\:* {behavior:url(#default#VML);} o\:* {behavior:url(#default#VML);} w\:* {behavior:url(#default#VML);} .shape {behavior:url(#default#VML);}@font-face {font-family:"Cambria Math"; panose-1:2 4 5 3 5 4 6 3 2 4;} @font-face {font-family:Calibri; panose-1:2 15 5 2 2 2 4 3 2 4;} @font-face {font-family:Tahoma; panose-1:2 11 6 4 3 5 4 4 2 4;} @font-face {font-family:Garamond; panose-1:2 2 4 4 3 3 1 1 8 3;} p.MsoNormal, li.MsoNormal, div.MsoNormal {margin:0in; margin-bottom:.0001pt; font-size:12.0pt; font-family:"Times New Roman","serif";} a:link, span.MsoHyperlink {mso-style-priority:99; color:blue; text-decoration:underline;} a:visited, span.MsoHyperlinkFollowed {mso-style-priority:99; color:purple; text-decoration:underline;} p {mso-style-priority:99; mso-margin-top-alt:auto; margin-right:0in; mso-margin-bottom-alt:auto; margin-left:0in; font-size:12.0pt; font-family:"Times New Roman","serif";} span.EmailStyle18 {mso-style-type:personal; font-family:"Calibri","sans-serif"; color:#1F497D;} span.EmailStyle19 {mso-style-type:personal; font-family:"Calibri","sans-serif"; color:#1F497D;} span.EmailStyle20 {mso-style-type:personal; font-family:"Garamond","serif"; color:#1F497D; font-weight:bold;} span.EmailStyle21 {mso-style-type:personal; font-family:"Calibri","sans-serif"; color:#1F497D;} span.EmailStyle22 {mso-style-type:personal-reply; font-family:"Garamond","serif"; color:#1F497D; font-weight:bold;} .MsoChpDefault {mso-style-type:export-only; font-size:10.0pt;} @page WordSection1 {size:8.5in 11.0in; margin:1.0in 1.0in 1.0in 1.0in;} div.WordSection1 {page:WordSection1;} ->@font-face {font-family:"Cambria Math"; panose-1:2 4 5 3 5 4 6 3 2 4;} @font-face {font-family:Calibri; panose-1:2 15 5 2 2 2 4 3 2 4;} @font-face {font-family:Tahoma; panose-1:2 11 6 4 3 5 4 4 2 4;} @font-face {font-family:Garamond; panose-1:2 2 4 4 3 3 1 1 8 3;} p.MsoNormal, li.MsoNormal, div.MsoNormal {margin:0in; margin-bottom:.0001pt; font-size:12.0pt; font-family:"Times New Roman","serif";} a:link, span.MsoHyperlink {mso-style-priority:99; color:blue; text-decoration:underline;} a:visited, span.MsoHyperlinkFollowed {mso-style-priority:99; color:purple; text-decoration:underline;} p {mso-style-priority:99; mso-margin-top-alt:auto; margin-right:0in; mso-margin-bottom-alt:auto; margin-left:0in; font-size:12.0pt; font-family:"Times New Roman","serif";} span.EmailStyle18 {mso-style-type:personal; font-family:"Calibri","sans-serif"; color:#1F497D;} span.EmailStyle19 {mso-style-type:personal; font-family:"Calibri","sans-serif"; color:#1F497D;} span.EmailStyle20 {mso-style-type:personal; font-family:"Garamond","serif"; color:#1F497D; font-weight:bold;} span.EmailStyle21 {mso-style-type:personal; font-family:"Calibri","sans-serif"; color:#1F497D;} span.EmailStyle22 {mso-style-type:personal-reply; font-family:"Garamond","serif"; color:#1F497D; font-weight:bold;} .MsoChpDefault {mso-style-type:export-only; font-size:10.0pt;} @page WordSection1 {size:8.5in 11.0in; margin:1.0in 1.0in 1.0in 1.0in;} div.WordSection1 {page:WordSection1;} -> --> OK, I don’t know that much about the way the double paned windows are made. It was just what I was thinking. Most of my experience in window glass is just from being a Real Estate agent. Being able to tell the difference between original glass in old homes and replacement<G> You would know this but most people don’t. glass is always a little bit liquid. Very old windows are slightly wider at the bottom than the top because the glass continues to flow over the years. Of course, that is not from experience working with glass, so you may debunk me, here, but it is something I read about in books about Vintage Homes back when I sold houses. BTW, I wanted to ask you. for a beginner in stained glass. Would you recommend copper tape or leading? Karon Adams Accredited Jewelry Professional (GIA) You can send a free Rosary to a soldier! www.facebook.com/MilitaryRosary www.YellowRibbonRosaries.com From: John Carmichael [mailto:[email protected]] Sent: Thursday, August 04, 2011 7:37 PM To: [email protected]; 'fer de vries'; [email protected] Subject: RE: mock stained glass sundial Karon: This I know to be true: Most window glass all have the same standard thickness of 1/8”. Large and small windows all use the same glass as far as thickness goes. Also, when double panes are used, they usually put the same air gap in all window sizes too. So the glass is the same and the air gap is the same for all sized windows. The bending of the light ray only occurs when the shadow hits the outer glass, so the distance between the nodus and the glass doesn’t affect the refraction. So I’m thinking the light will bend the same when it hit the outer glass on big and small windows. Since the hour and date lines are much closer on small dials, the time and date readings would be bigger on a small window. Let’s wait to see what Fer says (Fer is one of the smartest guys on our list). John From: karon [mailto:[email protected]] Sent: Thursday, August 04, 2011 4:15 PM To: 'John Carmichael'; 'fer de vries'; [email protected] Subject: RE: mock stained glass sundial But, John, if you have a larger window, the glass is thicker and the space between both panes would be more, wouldn’t it? that means not only is your refraction error larger but, since your angles arcs take up more space, the error is easier to perceive. Even if you have more error on a smaller piece, you would be less likely to notice it since the arc distance is so small. The larger and, therefore, more potentially accurate a sundial is, the more obvious any error would be. Karon Adams Accredited Jewelry Professional (GIA) You can send a free Rosary to a soldier! www.facebook.com/MilitaryRosary www.YellowRibbonRosaries.com From: [email protected] [mailto:[email protected]] On Behalf Of John Carmichael Sent: Thursday, August 04, 2011 7:04 PM To: 'fer de vries'; [email protected] Subject: RE: mock stained glass sundial Hi Fer: Your answer got me to thinking! It seems to me that the total size of the glass sundial face would have a huge impact on how significant the double glass refraction error is. I’m thinking that the bigger the sundial face, the less significant the refraction error would be. Follow my thinking in these two examples: Let’s say you have two faux stained glass sundials painted on the inner panes of glass, and both sundials have the same small air gap between the inner and outer panes. But one sundial is ten times bigger than the other sundial. Wouldn’t the amount of refraction be the same for both sundials since the air gap and the glass thickness is the same on each? If so, then the hour and date line error shift would be a lot smaller on the the big dial. Or to put it a different way- If the refraction shifts the shadow 1 cm, that would be less of an error on a big dial face than on a small dial face. Is my thinking wrong? Thx John p.s. From: fer de vries [mailto:[email protected]] Sent: Thursday, August 04, 2011 10:00 AM To: John Carmichael; [email protected] Subject: Re: mock stained glass sundial Hi John, I had to walk my room a number of times to know the answer but I think I do now. The glass panes add an error in the reading of the dial. As long as you don't change the thickness of the panes the x,y shift of a certain point is constant in values. Increasing the distance between the panes enlarges the dimensions of the sundial pattern. So relative the x/y shift has less effect on the reading and the error decreases. The same happens if you enlarge the distance from the outside pane to the index on the gnomon. Then also the dials dimensions increase and the error decreases. This is also an answer to Karons question about changing the thicknes of the glass panes. Then the x/y shift increases in values and an extra error is aded. Best wishes, Fer. Fer J. de Vries De Zonnewijzerkring http://www.de-zonnewijzerkring.nl Molens http://www.collsemolen.dse.nl Eindhoven, Netherlands lat. 51:30 N long. 5:30 E ----- Original Message ----- From: John Carmichael To: [email protected] Sent: Thursday, August 04, 2011 4:13 PM Subject: RE: mock stained glass sundial Thanks for checking on that Fer, making a drawing, and for correction my assumption. You taught me not to assume anything! I have a question though- Does the refraction error increase if the distance between the two glass panes increases? From: fer de vries [mailto:[email protected]] Sent: Thursday, August 04, 2011 1:29 AM To: Mike Shaw; [email protected]; 'John Carmichael'; [email protected] Subject: Re: mock stained glass sundial Mike, Your question: ***** If you are going to allow your shadow to pass through two panes of glass, will refraction start to become important? ***** John Carmicael answered: ***** It's insignificant. ***** My answer is: It is significant. Your statement is: .... shadow to pass through two panes of glass .... This means that the gnomon is at the outside of the double glass and the sundials pattern is at the inside of the double glass. As an example I calculated such a vertical south facing dial for latitude 45 degrees with hourlines and datelines. The double glass has panes of 5 mm and the space between is 15 mm. Rather normal values. The glass has a refraction index of 1.4 For the index for the datelines I have chosen a distance from the glass of 20 mm. I assume the refraction index of the space between the panes is 1. (No refraction). The pattern of the sundial is attached and shows a significant shift, especially for the datelines. (It is only 16 kB and should pass.) Black lines are without refraction, blue lines with refraction. Best wishes, Fer. Fer J. de Vries De Zonnewijzerkring http://www.de-zonnewijzerkring.nl Molens http://www.collsemolen.dse.nl Eindhoven, Netherlands lat. 51:30 N long. 5:30 E ----- Original Message ----- From: Mike Shaw To: [email protected] ; 'John Carmichael' ; [email protected] Sent: Wednesday, August 03, 2011 5:28 PM Subject: Re: mock stained glass sundial If you are going to allow your shadow to pass through two panes of glass, will refraction start to become important? Mike Shaw 53º 22'N 03º02'W www.wiz.to/sundials --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
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