Art Bianconi
Post Laureate
Reged: 03/06/06
Posts: 4659
Loc: Delaware River Valley, New Jer...
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Several times during my interactions with other mirror makers, the conversation arose as to the risk of continued exposure to cerium oxide.
Nobody wears gloves that I know of; your hands are constantly bathed in it while polishing so some focus on that exposure seemed warranted.
Today however, I came up against another potential hazard, the discovery of which may have answered a question I have asked myself. "Why do we use water when grinding mirrors?"
When you are standing there, doing little but squirting water at your turntable and sprinkling grit, you have time to ponder such things.
To wash the area for fresh grit? To keep the contact surfaces cool? To lubricate? Since I knew to add water, I did so obediently and didn't pursue an answer until today.
I was cleaning up the bench and turntable of the grit tailings from yesterday's grind. I was switching from 40 to 80 grade and didn't want the mirror to get scratched by a stray piece of courser grit.
As I brushed the area a large plume of dust arose from the table and came at me. I, not prepared for that, was without a mask and recognizing what the material was, abandoned the area in a hurry.
I've not ever heard this situation discussed in any ATM forum nor at any of the mirror making events local or distant. It appears that because the immediate area is always wet, there is no need for the precautionary warnings.
I have dust masks, good ones too that I wear prudently when sanding MDF because it's said to contain a known carcinogen.
Particles of carbide are sharp and if inhaled will likely cut the delicate membranes in the lungs. While they may or may not be carcinogens themselves, it has been shown that irritation of any region of the body makes it susceptible to a carcinogen from another source.
Assume nothing!
Art
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“Everything is on its way to somewhere. . . . . everything!"
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________________________ "Phenomenon"
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F8thful
super member
Reged: 06/14/05
Posts: 157
Loc: Camas, WA
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Not only does the carbide dust pose a hazard but glass dust poses the risk of silicosis
Check out this link
http://en.wikipedia.org/wiki/Silicosis
GR
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10" Dob project
New 10" 10 Yr. old Dob project
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mark cowan
Vendor (Veritas Optics)
Reged: 06/03/05
Posts: 3427
Loc: salem, OR
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Just use the KIWS principle, Art. Besides, water hydrolyzes the glass surface and makes grinding easier, as well as reducing the fracture size due to the chemical action of water in the tiny proto-fractures.
SFAIK wet CeO2 is innocuous, despite its typically small % of radioactive contaminants; SiO2 only poses a hazard if you breathe the dust & same for SiC - so keep it wet. But aerosols don't count, this is the source of the so-called "white lung" disease involving silica dust.
Best,
Mark
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Art Bianconi
Post Laureate
Reged: 03/06/06
Posts: 4659
Loc: Delaware River Valley, New Jer...
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Thanks Glen....Thanks Mark!
Art
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dromedar
super member
Reged: 06/11/07
Posts: 142
Loc: Σουηδ...
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Cerium sounded radioactive to me so i had to look it up the other day. http://en.wikipedia.org/wiki/Cerium dont know how dangerous it is but its probably not good to ingest it or inhale it, actually I dont think its a good idea to inhale any fine powder whatever it might be.
There are very fine diamondpowders these days, I've seen as fine as 1/20 micron, and I know 1/4 up to 10 micron or so is readily available. Could these be used instead of Cerium??
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Olivier Biot
Amused
Reged: 04/25/05
Posts: 24589
Loc: 51°N (Belgium)
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When polishing I don't think you want too fast material removal, so I don't believe you want to go for diamond powder.
Some prefer using very fine grit aluminium oxide.
A slower and much less 'dangerous' polishing agent (w.r.t. CeO) is rust (a.k.a. rouge). It's pure iron oxide.
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I think you're worth a double serving of happiness!
Tal-200K (#199) with JMI NGF-Mini2M focuser on GEM3 • Astro-Tech AT80ED • Orion Sirius EQ-G with wireless EQDIRECT • Astro-Tech Voyager • Celestron Regal LX 10x42 • Helios 15x70
ATM projects: 14" f/5 truss Dobson: first light Jul 1, 2011  - currently in 'tweak & widget' mode 
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Mike I. Jones
Carpal Tunnel
Reged: 07/02/06
Posts: 2874
Loc: Fort Worth TX
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Just Google the MSDS sheet for CeO2. Here's one hit, for example.
http://www.sciencelab.com/xMSDS-Cerium_IV_Oxide-9923351
Unless you're snorting the stuff or using it as a pizza topping, you're in more danger of dropping a counterweight on your toe than being hurt by CeO2
Mike
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56 mirrors, lenses, 16" f/6 Newt, 6" f/10 refractor, TOA-130S, Tinsley 5" f/15 Mak, 6" f/4 RFT, Coronado PST. Still to build: 24" f/10 Modified Dall-Kirkham, 10" f/26 Mak, 8" f/12 apo, spectrohelioscope, Herrig, Schupmann, and others.
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Achernar
Postmaster
Reged: 02/25/06
Posts: 7805
Loc: Mobile, Alabama, USA
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Cerium is not radioactive, but like any other heavy metal, I wouldn't want to inhale or ingest it.
Taras
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15-inch F/4.5 Homebuilt truss-tube Dob with Sky Commander digital setting circles.
10-inch F/4.5 Discovery Dob with JMI digital setting circles.
6-inch F/8 Homebuilt Dob
24, 18, 14, 11, 8.8, 6.7, 4.7mm ES 82 degree eyepieces.
21, 13, 8, 5 and 3.5mm Orion Stratus eyepieces.
Two Televue T-1 Paracorrs with tunable tops
Orion and Lumincon Deepsky, Ultrablock, O-III and H-beta nebula filters.
Three curious and needful cats
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mark cowan
Vendor (Veritas Optics)
Reged: 06/03/05
Posts: 3427
Loc: salem, OR
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Cerium is not radioactive, but the rare earths hang out together and as CeO2 is mined those less stable pals come along for the ride. Thorium, particularly, contaminates CeO2, in small amounts. Hard to seperate chemically. It does depend on the source, though.
SFAIK the Lanthanide series of rare earths (with Cerium) is NOT radioactive, the Actinide series (with Thorium) is.
Best,
Mark
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Ed Jones
Carpal Tunnel
Reged: 04/06/04
Posts: 2232
Loc: Sin-sin-atti
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Didn't Bob Cox have health problem as a result of his being around curve generators in his optics career?
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Ed Jones
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DAVIDG
Post Laureate
Reged: 12/02/04
Posts: 3663
Loc: Hockessin, De
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Yes, Bob Cox died of lung problems caused from a life time of inhaling the fine oil/glass dust mist that comes from high speed diamond generation of glass. This is different from a person working in his basement grinding optics were these very fine particles are not formed and then made airborn. Bob published a warning in Telescope Making about the problem a few months before he passed.
- Dave
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Homemade 'scopes 8"f/7,6" f/5", 6"f/4, 4.25" Schiefspiegler,60mm Coronagraph,60mm H-alpha system, 4.25" White-light Solar Newtonian,solar spectroscope, 4" f/12, 4.5" f/16 & 6" f/12 Schupmann Medial refractors, 4" Celestar, 19 Stellafane awards 9 in optics
Engineering = Taking what you have and making what you need.
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F8thful
super member
Reged: 06/14/05
Posts: 157
Loc: Camas, WA
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It seems to me that the health risks are going to be greatest during cleanup. It also seems that if the cleanup is done while the potential problematic dust is wet, the health threat will be minimized.
Just a thought
Glen
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10" Dob project
New 10" 10 Yr. old Dob project
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Art Bianconi
Post Laureate
Reged: 03/06/06
Posts: 4659
Loc: Delaware River Valley, New Jer...
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"It seems to me that the health risks are going to be greatest during cleanup. It also seems that if the cleanup is done while the potential problematic dust is wet, the health threat will be minimized."
This was the first time I'd ever cleaned up the day after and while the material was dry.
Up until this point it was always wet and a non-issue.
Art
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Bill Cheng
super member
Reged: 05/21/05
Posts: 185
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For some of us it's mostly affects one's mental health. Wear a mask for your physical health.
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Bill
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Gary Fuchs
Pooh-Bah
Reged: 05/22/06
Posts: 1288
Loc: Easton, PA, USA
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Art - We have some inexpensive dollar store spray bottles and mist some water over any dried areas before wiping up with slightly dampened paper towels. Also don't forget to rinse the glass and tool in a bucket so you don't have grit in your drain.
Gary
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Dick Parker
professor emeritus
Reged: 08/17/07
Posts: 732
Loc: Tolland, CT and Chiefland, FL
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Several years ago I got the brilliant idea of relaiming some of my abrasive by drying out the slurry and sifting it through screens. I abandon the idea quickly when I saw the fine dust generated by the process. Yes I did wear a respirator. Today I only reclaim my rough grinding grit, which is 60 grit, by water decantation. No dust produced. Even though it has been several years, I still shudder to think of what hazard could have been produced if I did not quickly think of the dust hazard. Moral of the story - don't ever let your guard down when it comes to safety.
Happy New Year. Dick Parker
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dromedar
super member
Reged: 06/11/07
Posts: 142
Loc: Σουηδ...
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I've found a site which carries a lot of abrasives
http://www.gravescompany.com/polishin.htm
could any of those on that list be used for making mirrors?
How fine is iron/ferric-oxide approx?
I know green chromium oxide is around 0.5 micron, is there anything to gain going lower than 3 micron cerium oxide?
I was thinking if you are new to this an even finer abrasive
taking longer time to work could be nice so you dont overdo stuff as easily.
Could fine powder be suspended in something else than water?
Like some oil maybe?
I know cleaned leather (you have to clean it otherwise there might be stuff on the surface that eats through things quite fast), leather is a really fine abrasive, maybe you could glue leather onto a pitchlap.
Well just some ideas, I bet most have been tried many times before.
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Art Bianconi
Post Laureate
Reged: 03/06/06
Posts: 4659
Loc: Delaware River Valley, New Jer...
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Gary wrote: ". . . . rinse the glass and tool in a bucket so you don't have grit in your drain."
The glass has wine in it. Good wine too so that's out.
I do rinse the tool in the bucket and then dump the contents of the bucket down the drain. Right?
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mark cowan
Vendor (Veritas Optics)
Reged: 06/03/05
Posts: 3427
Loc: salem, OR
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Just the water. Grit in drains turns into something like concrete in drains - I once heard a story about an optics lab in a university where drain disposal was the common method. Until the pipe solidified. Couldn't be snaked, had to be taken out through the wall. Or was this in a basement??? 
Best,
Mark
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Art Bianconi
Post Laureate
Reged: 03/06/06
Posts: 4659
Loc: Delaware River Valley, New Jer...
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"Just the water. Grit in drains turns into something like concrete in drains "
I was just joking Mark.
I sweep the tailing's and whatever lands on the floor into an empty paint bucket and when It's full I hammer the cover on tight and bring it to the transfer station.
Then I come home and drink the wine.
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