It's a no brainer to wear clear safety glasses when we are using the drill, sanding, etc. What about when we are using the torch, the kiln, etc? This is a topic often unaddressed or better yet, often riddled with incorrect info. I wish that I had this information years ago, so I want to share it with you!
I've looked in numerous books including the top safety books and there really wasn't anything that addressed eye protection other than the obvious safety glasses. This is unfortunate. It's such an important topic, one that should always be included, especially if you teach.
I create with many different mediums so my exposure to safety has been more varied than most. With the exposure to these mediums, my past teachers and vast research, I was able to piece together, all the good and the bad information on eye protection.
I was also fortunate to be part of a discussion on a forum regarding eye protection several years ago. Mike Aurelius who owns AuraLens was one of the participants in the discussion. He owns a company that sells eyewear to lampworkers, furnace workers, and other hot shop workers.
Through the series of conversations, I have pieced together this information to share with you as he sums it up best. Below is the important information he shared in the conversation.
The Ins and Outs of Eye Protection and Lense Coverage:
"It takes at least 4000°F to start generating UV (although certain metals and glass types do generate uv, based on the elemental composition of the meta/glass). The major issue is IR, but only when the size of the object being heated is about the size of your fist and the temperature of the surround (such as the inside of the kiln ) is in excess of 1000°F.
Most optical material today does an adequate job of filtering UV rays. Even plain safety glasses will provide all the UV protection you need. Since a kiln IS larger than your fist, this is where the welding shades do become important.
Propane by itself burns at 3200°F, propane/air at 3500°F and propane/oxygen at 3800°F. It's more the *mass* of the heated objected AND the size of the flame that matter.
When you are soldering you are heating a small area and using a small flame. A flame this 3" long is relatively IR *safe*. A flame that is 8" long is relatively IR *unsafe*.
Another point to remember is that the intensity drops by the square of the distance. The further away you are, the less the intensity. An easy guideline to follow is that if you can feel the heat on your cheeks and/or forehead, you need protective eyewear.
When you are soldering using a hand torch, as has been noted, there is a very small flame and a very small area being heated. There are no hazardous emissions of UV, visible, or IR energy that you need to worry about.
didymiums on the left and safety shade 2.5 green on the right
Some jewelers prefer to use a filter lens, such as didymimum or ACE (Aura -92). These filter lenses remove sodium wavelengths (known to glassworkers as sodium flare), also known as sodium yellow.
Sodium flare comes from a variety of sources in soldering, but is mainly in the flux. If you have a fairly large ball of yellow flame, removing the yellow will allow you to see through the flame and see your work under the flame. Again there is nothing hazardous about sodium flare. It is not harmful to your eye.
There is also another class of filters, called variously Calobar, Welder's Green, etc. Calobar is no longer manufactured, however, filter equivalent spectacles are available from a variety of sources.
Shade 2.0-2.5 is the most used filter number in this particular filter by crafters and hobbyists. Shade 2.0-2.5 allows maximum light transmission (about 35%) and a minimum IR transmission(less than 10%).
This filter is most used when viewing intense heat sources such as kiln, furnaces, and glory holes. We don't recommend its use for torch applications unless you are actually cutting metal with a torch, and then only the required shade number for the thickness of the metal being cut.
Enamelists will find this filter useful when observing and manipulating their work in a kiln.
Borosilicate glass (pyrex) works at a much higher temperature than soft glass, plus the colors usually contain metals that burn off during the working process. On the average, pyrex glass workers usually use a true shade 4.0 or higher, depending on the size of the piece being heated. Those who do small bead work can usually work with a shade 3.0, while those who do sculptural work generally are working with a 5.0 or better. Additionally, pyrex also has a silica component, so a base of ACE or didymium is also required to see through the sodium flare as well."
At Whole Lotta Whimsy we sell 2.5 Safety Shade glasses. They only allow 2.5% IR transmission which is the nominal amount. They are a must have for those with a kiln or Ultra Lite. Plus they have the side safety shield which is always recommended. Hope you find this helpful. Please share it with your students and friends.