January 2002 Volume 24 Number 1
Sometimes it's not easy being a Health and Safety column editor. I had a rough October.
First, at the WAAC Annual Meeting, there was the searing question—"In that slide of you pressure washing that mural, were you wearing safety goggles?"
Busted. Guilty. And shamed because it never occurred to me, your WAAC Health and Safety column editor, that I should wear eye protection while pressure washing a mural. Of course I should have been wearing goggles. It was so obvious, so glaring, so wrong. Suffice it to say, I will never pressure wash (or pressure anything for that matter) in the future without safety goggles securely planted over my baby blues.
Discussing my shame at the WAAC board dinner, WAAC VP, Mitchell Hearns Bishop noted that often people who wear glasses overlook eye protection. Not on a conscious level, but at a more primal level. Kind of in a reverse Pavlov's dog sort of way. Those occasional everyday occurrences where things head towards your face and you instinctively flinch. Those of us who wear glasses flinch just the same, but are often greeted by the reassuring sound of "click" as the offending whatever bounces off a lens.
Which kind of brings up the question, at least for those conservators saddled with glasses: What type of lens should I get? My recommendation is still polycarbonate. According to the Polycarbonate Lens Council information site (probably not altogether impartial) it is the most shatter resistant specular lens material. It is already "high index" so it works well for heavier prescriptions. Polycarbonate is also the standard for safety goggles.
Polycarbonate lenses are also said to be UV (ultraviolet radiation) absorbing and opticians will tell you that there is no need to add UV filtering to the lenses. This claim is also made by the Polycarbonate Lens Council. And I have recommended in previous columns that wearers of polycarbonate lenses probably don't need to wear additional eye protection when working with long-wave ultraviolet light.
Of course, it's not that simple. Testing my lenses with a UV light meter, I found that the level of UV transmitted was much higher than I would have expected for a "UV filtering" material. I sent an email to the Polycarbonate Lens Council some weeks ago asking about this observation and have not yet received a reply. I checked some other eyeglasses with the same meter and found that some lenses do indeed block almost all of the UV present in direct sunlight.
[As an aside, I've found similar conflicts between claims of UV filtering in
laminated window glass and actual measured UV levels. In the case of polyvinyl butylral, the laminating agent, the polymer is not inherently UV absorbing. It is modified with light stabilizers which absorb the UV. The product specification claims absorption of 99% of UV below 380nm however I have measured UV levels with a Meaco Lux & UV Meter through these glasses with UV transmissions from less than 1% to 14% to as high as 20%.]
So the moral is: check your glasses, check your light levels, check that the UV absorbing glazing you've purchased does.
I will look into the question of lens materials for a future column. However, of possible interest and utility, The Polycarbonate Lens Council offers a "UV Sensometer Card" which they provide for $4.95 shipping and handling. Intended to evaluate the UV protection of your present glasses, the card appears to have a UV sensitive material that darkens on exposure. By using the comparison chart you can determine the relative amount of UV transmitted through your glasses. I've just mailed in my order so I can't say if it really works, but this might be of some utility to conservators trying to determine if glazing materials do indeed block UV. Hey, you can even check out your eye glass lenses. [You can download the UV Card Order Form from http://www.polycarb.org/uvorder.htm.]
Yet, I digress. Busted: Last issue, I mentioned an incident where I inadvertently rolled a scaffolding into low-hanging, power lines. Fortunately, there was no harm done beyond the scare and embarrassment. It was really stupid. I try to keep the subjects covered in this column rooted in the practical. I often discuss aspects of my own conservation practice not merely to talk about myself, but to allow me to offer real world examples of problems and solutions.
Monona Rossol, of Arts, Crafts and Theater Safety (ACTS) was kind enough to send me a letter explaining the seriousness of the violation of scaffold safety regulations I had committed.
She wrote that one is not allowed on a scaffold unless there is a certificate-holding "competent" person present. This person must be trained on all the regulations regarding scaffolding safety including those relating to power lines. The competent person must survey the area and identify any power lines and their voltage. This is also the person who would call the power company and arrange to have them temporarily de-energized if the scaffold would ever be anticipated to be within the distance allowed.
The rules the competent person follows are in OSHA Regulations ( Standards—29 CFR) 1926.451 Subpart L—Scaffolds, paragraph (f) (6).
The clearance between scaffolds and powerlines shall be as follows: Scaffolds shall not be erected, used, dismantled, altered, or moved such that they or any conductive material handled on them might come closer to exposed and energized power lines than as follows:
|Insulated Line Voltage||Minimum Distance||Alternatives|
|Less than 300 volts||3 feet (0.9 m)|
|300 volts to 50 kv||10 feet (3.1 m)|
|More than 50 kv||10 feet plus 0.4 inches (1.0 cm) for each 1 kv over 50 kv||2 times the length of the line insulator, but never less than 10 feet|
|Uninsulated Line Voltage||Minimum Distance||Alternatives|
|Less than 50 kV||10 feet|
|More than 50 kv||10 feet plus 0.4 inches for each 1 kv over 50 kv||2 times the length of the line insulator but never less than 10 feet|
Monona went on to state the need to impress on our profession that conservators legally cannot get up on a scaffold without being directed by a certificate-holding competent person. Conservators could take the necessary training course to become the competent person. However, she points out that the courses are tough, expensive, and you need to retrain annually.
Thank you, so very much Monona for writing. I will get my scaffolding house in order. Everyone working on or with scaffolding should be in compliance with the appropriate OSHA regulations, covered by CFR 1926.451 Safety and Health Regulations for Construction: Subpart L—Scaffolds. It all is available on-line at: http://www.osha-slc.gov/OshStd_toc/OSHA_Std_toc_1926_SUBPART_L.html (note that there are underscore characters between each word in the URL) and the sub-pages following.
On a less grave note. Also in the last column, I flippantly said "...Formica: I don't even know how to look that one up." Fellow AIC Health and Safety committee member Mary W. Ballard, Senior Textiles Conservator at SCMRE, the lab formerly-known-as-CAL, emailed the following note. It's such great information that I can't resist publishing it here.
Chris—in your WAAC article, you wrote you weren't sure of the formula of Formica. It's a cross-linked melamine-formaldehyde polymer resistant to most organic solvents. Somewhat effected by acids & bases. I have learned & forgotten the synthesis several times over the years but it's pretty easy: looks like a benzene ring with every other carbon substituted with a nitrogen. It's called a triazine; it has the same alternating double bonds as benzene. On each of the 3 carbons is a substituent amino (NH2) group and get cross-linked by reacting with formaldehyde. Once everything is reacted, it's pretty much a dense, unreactive polymer. This chemistry is related to "durable press" resin, no iron cotton, and also to the reactive/covalent bond in reactive dyes. Unless you wear only white clothes, chances are the dyes of your clothes are mostly bonded to the fiber with a variant of this system that had a chlorine where the amino group was. Usually, there is just one ring, dye on one side, cellulose on other, the other endgroups are H2. The killer for Formica is grape juice. For the reactive dyes, Clorox bleach (but that usually kills the azo n=N groups of the dye, not the covalent bond or the triazine ring). Shall I send you the formulas sketched out? It's pretty neat. Happy New Year. Mary
Thank you, Mary. Now we know.
Timestamp: Thursday, 11-Dec-2008 13:02:36 PST
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