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Re: lampwork demos:veiwer eye protection

Posted By: Mark Eliott
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
: expensive.

: Brad

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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