Where do these come from?
Some of the boro colors will generate UV when they are really hot. The lenses used for working with soft glass are not made to block UV. You need both UV and IR protection when working with boro, especially boro color.
Ummm, no. Nothing we normally work with generates UV (Ultraviolet) until it reaches a temperature of about 4,500 F. Since propane and oxygen run about 3,800 F, you can’t get your piece hotter than that. None of the elements that burn off in the flame will generate UV either.
The single sole source of damage to the eye from working boro is IR (infra-red) or heat energy. There are some visible light issues as well, as detailed here: http://mikeaurelius.wordpress.com/2007/12/25/visible-light-hazards-and-the-glassworker/
According to one website, the lens is very efficient in filtering sodium flare in addition to providing UV protection to 390 nm. So they are indeed made to block UV.
Back in the 1980′s all ophthalmic glass was reformulated to bring the filtration line closer to the UV-VIS line at 400 nm. Information from the medical professions was starting to indicate a trend that showed that sunlight UV was causing damage to the eye with long term exposure. The glass manufacturers were the obvious place to increase the filtration levels by the addition of certain key elements in the glass. All of the currently available plastic materials (CR-39, polycarbonate and the high index plastics) filter UV to about 380-390 nm, and therefore need no extra coatings to increase UV protection to 400 nm.
The scare about near UV (370 to 400 nm) is a S-C-A-M. It has been foisted off on the spectacle wearing public as an easy way to make extra bucks on the eyewear by the dispensing optician. The best way to handle this situation with your optician when he tries to sell you optical coatings to protect up to 400 nm is to ask him/her: If 400 nm is considered safe for the eye, how can 390 nm be hazardous? How can 380 nm be hazardous? Why is 400 nm the magic number between hazardous and non-hazardous. The correct answer is that there is no magic number. It is a range, not a fixed number. Some people can actually see below 400 nm! Now, the closer you get to 350 nm, the higher the hazard to the eye becomes. So, the bottom line is that if you are wearing your spectacles outside, you want protection at about 350 nm. If they try to sell you the panacea (snake oil!!) of UV-400, just thanks but no thanks. It just plain isn’t necessary.
I would be interested to know what the general thinking was with regard to the “standard” didymium/ACE lenses. Okay for soft glass beadmaking (as far as I know) but are these okay for boro work using, say, a minor burner? I get the occasional question relating to this and I don’t have a specific answer.
I also don’t know what the problems are with too much IR radiation. I understand it to be increased risk of cataracts and detached retina, but would be grateful for clarification on this.
The issue with small torches and boro is still a matter of IR to a certain extent, but more the visible light flares from the various metals burning off. That is the reason welding filters are used, both for the visible light flares as well as the IR filtration.
As far as eye hazards, detached retina is **NOT** one of them. Detached retinas are much more likely to result from an impact to the head. Cataracts, retinal and corneal burns are the chief medical woes. And everyone must remember that the damage is cumulative and everyone has a different threshold for damage to become apparent. There also appears to be a genetic issue at play as well: the typical “nordic” blonde, blue-eyed (as well as red-head green eyed) person is going to be a lot more suseptible to eye injury than your mediterranian/hispanic/asian/african person would be. IMO it is the amount of melanin in your body that seems to affect the amount of IR that the body can stand.
IR is the main hazard, but UV light is produced by some of the boro colors when they are really hot. In the eye UV exposure can increase the risk of cataracts, corneal burns, retinal damage. It’s not an issue with soft glass or clear boro, jsut some of the metals used in boro color.
I’ve said it before and I’ll say it again: UV radiation is **NOT** generated until the temperature of (anything) gets to about 4,500 F. Since a propane-oxygen flame is only about 3,800 F, there is no UV radiation generated.
It is not the metals. No, really it is not. It’s not the glass. It is, pure, plain and simple the temperature. It is IR radiation. It is heat energy. The glass (and the flame) are not hot enough to generate UV, so it is only IR that causes the problem.
I don’t wear “boro” glasses to work boro. I own some, but rarely use them. I torch in didies over my prescription lenses. Having two sets of lenses does help with the IR. IR sounds all scary and stuff, but in plain English, it’s heat. You can feel IR on you skin. As you start to work bigger, your exposure increases. I’m not sure working smaller is dangerous no matter what glass you’re melting.
1) Wearing two pairs of glasses does **NOT** help with IR. Clear glass/plastic/polycarbonate transmits about 98% of IR. ACE/AUR-92/Didymium transmits about 92% IR. So if both materials transmit in excess of 90% IR, your eyes are being exposed to IR.
2) Yes, if you can feel the heat on your skin, that same heat is being dumped into your eyes. The only difference is that the eye does not have heat receptors. It cannot tell you when it feels hot until it is far too late.
3) If the IR is present, you are being exposed to it, regardless of the size of the piece you are working. You will feel more heat on a large piece, but that is because there is more mass to radiate the heat. There is still “something” in front of you that is radiating heat of at least 1800 F, and that amount of heat is enough to cause problems with your eyes.
Not trying to question you, but I’ve read several different sources that say an oxygen-propane flame is in the neighborhood of 5000 F. None of them were specifically talking about lampworking torches (most were cutting torches) but if that were the case, would there be any UV problems?
The maximum burning temperature of propane is about 4,300 F.
It’s been typically recognized that the average propane-oxygen torch burns around 3,800 F.
But its important to note here that the borosilicate glass is not reaching that temperature, and therefore cannot generate UV.
The working temperature of boro is a little over 2,200 F. Working temperature is the temperature at which the glass is “loose” and able to be shaped and formed. Temperatures much beyond 2,300-2,400 F will result in the glass either boiling or liquifing.
Softening point is 1,500 F. Softening point is the temperature at which the glass changes from hard and inflexible to soft and flexible.