Yup, I know the sucking eggs saying. We used it on the farm when I was a kid but, we were teaching cats to suck eggs as they were often the miscreants involved<G>
Yes, I have used that book many times when making things with various metals. I love some of the cool patina colors you can generate. My favorites are some of the beautiful heat patinas I can create on copper!. Those are FUN! But always a challenge to keep. Even with waxes and polish, they still fade over time. Too bad but, the nature of the beast. I knew you would know all this, I was just pointing it out for some of the other folks who may not work with precious and semi precious metals. I never did show you a pic of my first sundial. I coated it with a mixture of salt and vinegar. Put a crust on the whole thing for a couple of days, then, wiped it all off. The left over salty vinegar settled in the lines (which was my goal). Looks very cool. I still need to wipe it down. I COULD say I have been 'waiting' and 'allowing nature to work her magic' but, the truth is, I have just been lazy and distracted and didn't want to go outside in 105 degree temps<G> I am planning to wipe it with polishing cloth to clear the random green markings but try to leave the green in the hour lines. Then I'll polish over the whole thing with a sealant. I have not yet decided which one I want to use. Especially since this is an experimental piece, the first one I have made. And, I'll never forget how BLINDING the thing was when I first finished it and took it outside! Nope, no sundials on a mirror unless you are making a reflective sundial. But, even then, you cannot read the time on the mirror<G> Most of my metal work is in jewelry where we are avoiding oxidation (don't want a finger or neck turning green<G>) or small sculpture where you may or may not want patina. But, you have to plan for patina cause you really cannot escape it if you are working with any metal<G> Karon Adams Accredited Jewelry Professional (GIA) You can send a free Rosary to a soldier! www.facebook.com/MilitaryRosary www.YellowRibbonRosaries.com > -----Original Message----- > From: Tony Moss [mailto:[email protected]] > Sent: Tuesday, August 16, 2011 1:17 PM > To: [email protected] > Cc: [email protected] > Subject: Re: Minimum size (was Re: the nature of time, was RE: UTC Conference) > > Karon, > I've worked most common metals at many levels of skill for > 60+ years so I'm not unfamiliar with patination. No doubt you are > acquainted with "The Bronzing, Colouring and Patination of Metals" by > Hughes and Rowe which has been my immediate resource in such things. > > Just one pointer from my own years of making metal dials in everything > from bronze to stainless steel, *polishing* is the very LAST thing they > need because "You can't cast a shadow on a mirror" > > I usually gave clients the choice between bare metal to acquire a > natural atmospheric patination or a light chemical 'bronzing' with a > commercially available solution. Followed by waxing with the wonderful > Renaissance conservators' wax from Picreator products > > http://www.picreator.co.uk/ > > With occasional washing and re-waxing this encourages the growth of a > glossy natural coating which holds a shadow beautifully. > > Apologies if I seem to be 'teaching my granny to suck eggs' here (I hope > that means something US side). > > Tony Moss > > > On 16/08/2011 15:40, karon wrote: > > That made me think of something else. Extremely precise dials with tiny > > subdivisions marked would also have long term inaccuracy problems brought on > > by oxidation, also known as Patinas. When oxidation occurs, it actually > > creates expansion (in most cases) of the material oxidized. So, the > > precision of the lines is slightly altered by the growth of the oxidation. > > Never mind what else may grow on the piece. It is a tiny amount but, if we > > are talking very tiny tolerances, those tiny amounts created by oxidation > > effects the precision of the piece. But, to prevent that, you have to polish > > regularly. And, even doing that, you remove tiny amounts of material with > > each polishing, thereby changing your precision in reading ability. > > > > All of this is 'over time' but it exists. When you walk up a stone > > staircase, you are unaware of the miniscule amount of stone that rubs onto > > your shoe. But, there have been so MANY people walk the steps of a place > > like the US Capital, here in the US, that the Capital Hill Police > > Department, in their mock ups of the building used for training, have had to > > build the steps with dips in them to match the ones in the steps. You also > > see this in very old cathedrals. Places where millions of steps down an > > aisle create a path. Now, on a sundial, the process is slower, the effects > > are the result of weather and wind but those are the things that carved the > > world. > > > > I think we have to accept that precision is possible in creation but, in > > use, practically, we cannot expect a sundial to be the same kind of time > > piece that an atomic controlled time piece would be. But I don't think > > anyone expects it to be so. > > > > Karon Adams > > Accredited Jewelry Professional (GIA) > > You can send a free Rosary to a soldier! > > www.facebook.com/MilitaryRosary > > www.YellowRibbonRosaries.com > > > > > >> -----Original Message----- > >> From: [email protected] [mailto:[email protected]] > > On > >> Behalf Of Tony Moss > >> Sent: Tuesday, August 16, 2011 8:50 AM > >> To: [email protected] > >> Subject: Re: Minimum size (was Re: the nature of time, was RE: UTC > > Conference) > >> Hi All, > >> > >> Some while ago I bought a brand-new, tiny brass horizontal dial in a > >> shop which sells things like clock inserts and thermometers to include > >> in hand crafted items. It cost around £1.00 as I recall. > >> > >> The dial is 2.5" in dia. and is clearly calibrated in 3 minute intervals > >> with every five minutes actually numbered, although it took a magnifying > >> glass for me to be sure of the detail. A fully-readable circular > >> Equation of Time is of a style which suggests a re-worked C18th? sundial > >> of some quality: there is no maker's name. The dial has been made by > >> photo-etching which experience suggests is deep enough to survive for > >> several years outdoors if cleaned and waxed regularly. A stamped brass > >> gnomon was included but seems to have gone astray - grandchildren > >> probably! :-( > >> > >> Polished brass is devilish stuff to photograph but I've take a couple of > >> close-ups for the curious. > >> > >> Tony Moss > >> > >> P.S. When I get a moment I'll make an enlarged print and find out the > >> intended latitude. > >> > >> P.P.S. Why didn't I buy 50! ;-) > >> > >> > >> > >> > >> > >> On 16/08/2011 10:06, Jackie Jones wrote: > >>> To know that the 2 minutes have passed, they have to be marked on the > > dial > >>> face. This introduces the practical problem of how fine a line can be > > made > >>> and still see it without it blurring into the next 2 minute line. The > > finer > >>> a line is marked on the metal, the less likely it is to remain and not > > get > >>> worn away. I have just tried it with a hand engraving tool on a scrap > > of > >>> silver and I can get 3 lines in 1 mm. But they are very fine and you > > need > >>> good eyesight to see them well. To engrave a line deep enough to last, > > I > >>> would suggest a minimum of .5mm apart. This is easy to see; this is > > what is > >>> marked on most steel rulers. > >>> Looking at the portable dial pictures in Hester Higton's book, there is > > a > >>> Butterfield dial by John Rowley which is marked to 5 minute intervals. > > This > >>> is possibly the nearest one can get in practical terms to engrave clear > >>> lines on a dial of that size - I think they are about 5cm dia. > >>> Therefore, I would not think it practical to mark 2 minute intervals on > > a > >>> 2cm diameter dial. There is a signet ring dial of about this size in > > the > >>> above book; this is divided into hours, but with finer lines, there > > could be > >>> half and quarter lines between. > >>> Jackie > >>> > >>> -----Original Message----- > >>> From: [email protected] [mailto:[email protected]] > > On > >>> Behalf Of Steve Lelievre > >>> Sent: 15 August 2011 22:27 > >>> To: [email protected] > >>> Subject: Minimum size (was Re: the nature of time, was RE: UTC > > Conference) > >>> On 15/08/2011 3:52 PM, karon wrote: > >>>> <snip> the smaller [sundials] are, by definition, > >>>> the less precise they can be.<snip> > >>> This statement got me wondering how small can a sundial be, before > >>> hitting the limits of our visual acuity. Here's my thinking: > >>> > >>> Shadow blur imposes a limit of about 2 minutes of time, because the > >>> sun's diameter is half a minute of arc. 2 minutes of time = 1/720 part > >>> of a day. The human eye can resolve about 0.00349 inches (about 0.09 mm) > >>> at 12 inches (30 cm). This figure comes from > >>> http://www.ndt- > >> ed.org/EducationResources/CommunityCollege/PenetrantTest/Intr > >>> oduction/visualacuity.htm. > >>> Of course, it is not really the correct value to use because (i) most > >>> users don't have perfect eyesight (ii) a dial face almost certainly does > >>> not provide the same viewing qualities as the printed monochrome grid > >>> used for testing human eyesight. But it's all I've got so I'll use it > >>> anyway. I conclude that a horizontal dial with circumference of 720 x > >>> 0.00349 inches should be resolvable to 2 minutes of time. Multiply out > >>> and divide by pi to get the equivalent diameter. > >>> > >>> The result is just under 0.8 inches diameter = 2 cm. > >>> > >>> OK, so there's an inadequate theoretical value; does anyone know the > >>> real, practical lower limit for size of a horizontal dial that still > >>> achieves 2 minute resolution? For instance, how small do portable > >>> horizontal dials get before they lose resolution? > >>> > >>> And the converse question: what was the typical range of sizes of > >>> antique portable dials, and how does that range compare to the size > >>> required to achieve the best possible precision? (I think I mean > >>> precision not accuracy, but I may have the two words confused). > >>> > >>> Cheers, > >>> Steve > >>> > >>> > >>> > >>> --------------------------------------------------- > >>> https://lists.uni-koeln.de/mailman/listinfo/sundial > >>> > >>> > >>> --------------------------------------------------- > >>> https://lists.uni-koeln.de/mailman/listinfo/sundial > >>> > >>> > >> --------------------------------------------------- > >> https://lists.uni-koeln.de/mailman/listinfo/sundial > > > > --------------------------------------------------- https://lists.uni-koeln.de/mailman/listinfo/sundial
