A question from the field

I purchased a pair of your glasses 4 or more years ago. Lately, I’ve noticed that my eyes are hurting when I am done at the end of the day. Does the filter material “wear out” over time?

Answer: No. The filter elements are part of the glass matrix and cannot/do not fade. Welding filter glass uses iron as the major filtering element. AUR-92/ACE glass uses didymium/neodymium/praesodymium plus other “rare earth” elements. These elements are mixed in with the silica when the glass is being melted by the manufacturer.

The manufacturer of the glass routinely tests its glass over time, keeping samples of each melt and subjecting them to various tests to determine transmission over time and exposure. Schott Glass Technologies, for example, has samples of didymium that go back over 50 years, and that glass still has the same transmission characteristics that it had when it was first made.

What is more likely is that over time, your skills have improved from the time you first bought your glasses. You may be working longer hours, you may be using different techniques, and you are certainly working with different formulations of borosilicate glass (especially the colors). You may also be doing more fuming now than you did when you first got your glasses.

The bottom line is that you have perhaps “out grown” your current filters and most likely need something with more filtration.

What does cataract surgery cost?

Per eye, approximately $7,200.

My mother, still “young” (in her early 70’s), just had cataract surgery in both eyes over a two month period of time.

$14,400 for both eyes. Plus not having perfect vision for up to 2-3 weeks afterwards, having to avoid bright lights for 6-8 weeks. If my mother had been a torch worker, she would have been out of work for close to 4 months.

Energy Radiance Information for Glassworkers

NIOSH and OSHA have determined that the IR TLV (threshold limit value) to the unprotected eye is 10 mW/CM2 for time periods greater than 16 minutes. (10 mW is .010 Watts)

Air temperature and altitude corrections for ventilation systems

Altitude and air temperature make a substantial difference in the performance of any ventilation system. The calcuations I have provided here: http://mikeaurelius.wordpress.com/2007/12/25/ventilation-basics-part-two/ are based on sea level and 70 degrees F.

In the calculations, the only variable that needs modifying is VP, Velocity Pressure. The standard calculation is (V/4005) squared.

When applying temperature and altitude corrections, use the following equation: VP = ((V/1096.7) squared) times ‘density of the air in pounds per cubic foot’.

Ventilation question

From the ISGB forum:

Hi , right now I’ve been using the system Vince described in the Drew Fritts book. I had been using a minor and everything worked well.
Recently purchased an Lucio torch from Carlisle. I noticed I needed to upgrade my ventilation system. So I like to start from scratch, build a new hood etc. My room is 8 x 24.
I have also read an interesting article, and would like to get your thought on it please. Here is a link.
http://andreaguarino.com/ventilation/

I took a look at Andrea Guarino’s website and the link on her ventilation system. If you are a regular reader of my blog, you know my feelings on open duct ventilation (I don’t believe they work and don’t recommend them).

Plumbing for propane

From LE:

My studio is a separate building and my propane tank and regulator are in a ventilated box my husband built sitting on a ledge attached to the outside of the building. He ran the standard hose that came with the torch (or I my have purchased it separately) through a small hole about a foot from the floor which is about 4 feet to my torch. The small hole has a pvc pipe inserted with the hose running through it and then a wood plate on the ouside and inside holding it in place. The hose also has insulation stuffed around it. Okay, now it all looks fine to us – but the experts out there, are we missing some important safety concern? Thanks in advance!

On the surface, this sounds like a marvelous idea. Make a hole in the wall, line it with PVC, insulate it, and run the rubber hose through it.

Unfortunately, it is an illegal installation. The National Fire Code (NFPA) states that all wall penetrations must be accomplished with hard wall metallic piping. The piping can be copper, black (iron) pipe or stainless steel. There must also be a shut off valve on either side of the wall. On the inside of the wall, the pipe must extend to within 5 feet of the point of use, and if the point of use is further than 10 feet from the inside shut off valve, the line must have an additional shut off valve at that point (torch valves do not qualify).