Re: lampwork demos:veiwer eye protection
Posted By: Mark Eliott In Response To: Re: lampwork demos:veiwer eye protection (Brad S)
Date: 4/28/2003 - 9:41 a.m.
In Response To: Re: lampwork demos:veiwer eye protection (Brad S)
: I tend to agree that there probably isn't much danger to the casual lampwork
: demo viewer. Since the intensity of light and heat falls off with the
: square of the distance from the source I don't think doing long term
: damage to the eyes of lampworking spectators is something one needs to
: worry about a great deal. In other words, the person doing the
: demonstrating, assuming a 1/2 meter distance from his/her eyes to the
: work, is subjected to 36 times more light/heat intensity than someone 3
: meters away. The exposure time for spectators is also quite limited.
: Colored boro presents another problem as the oxides used to color it can
: throw off a lot of light at the working temperature. The intensity and
: wavelength of that light (IR/UV?) and its ability to do eye damage to
: spectators is a good question, as it varies with the oxides used to make
: the different colored glasses.
: A very cheap and easy protective screen can be made from aluminum (aluminium
: for our overseas friends) window screening. It cuts down both the heat and
: light transmitted to spectators and still allows the demonstrator to talk
: to people through it. Anyone who has demonstrated lampworking while trying
: to converse with people from behind a solid screen of some type, such as
: plexiglas, will appreciate the difference in the ability to hear people in
: the audience. Window screening is also very effective in keeping flying
: glass out of the audience. That should be the first and foremost spectator
: safety concern when demonstrating, along with keeping inquisitive fingers
: away from the hot glass on the benchtop. Not trapping the torch heat
: behind the screen to create a personal sauna for the demonstrator is
: another benefit.
: I don't personally know of any material that comes in large affordable sheets
: that will cut the sodium flare like didymium glass does. Maybe there is
: something that someone else out there knows about. But standard didymium
: glass only blocks the sodium flare and light emitted between the
: wavelengths of about 540 and 580 nanometers. It lets a large part of the
: other light, including nearly all of the infrared, through it. One
: possible alternative to didymium that I can think of is a standard
: neodymium sheet glass. "Didymium" is a combination of neodymium
: and praseodymium. Neo is the oxide primarily responsible for blocking the
: "sodium flare", so you may want to check with Bullseye or other
: stained glass manufacturers to see if they have anything that might do the
: job. Neodymium sheet glass might come close and would probably be
: available at a reasonable price.
: You could also try to find a smaller piece of didymium plate glass to hang on
: your screen. That would give the spectators (at least some of them) a way
: to see the difference in what you see with didymium glasses and what they
: see without them, which a lot of people seem to find interesting. I would
: think a full piece the size of your screen would be prohibitively
Thank you so much Brad you have given me heaps to think about and follow up on. This discussoin board is a neat Idea, Best regards, Mark.
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