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**JohnKSa** · July 4, 2006, 10:28 PM

"Exposure Level #1:
X-rays can easily penetrate paper and cloth but can not penetrate denser materials such as rubber, glass, wood, or metals (aluminum, steel, and lead). "
http://www.coe.uga.edu/mse/science/o...ys/x-rays.html
"To block stray radio waves emitted by the detector's circuitry, the FPD was encased in a thin aluminum skin, which is almost transparent to x rays but opaque to radio. "
http://www.aip.org/pt/vol-58/iss-6/p22.html

"A typical X-ray will penetrate through thin layers of aluminum,
and eventually be absorbed by the material."
http://www.madsci.org/posts/archives...3690.Ph.r.html

Quoting is hard since this is a pdf, but do a search on aluminum and find a very brief description on how aluminum is used to calibrate dental X-Rays by comparing it's known density on the images to other objects in the image.

http://www.sciencenews.org/pages/pdf...9/15319-15.pdf

"Calibration procedure of aluminum wedge by optical density gradient of its X-ray image "
http://www.ncbi.nlm.nih.gov/entrez/q...&dopt=Abstract

"Aluminum alloy wedges are used to standardize x-rays"

http://lsda.jsc.nasa.gov/scripts/har...ardware_id=777

"Aluminum FB (foreign bodies) can often be visualized on radiographs"

http://www.ncbi.nlm.nih.gov/entrez/q...&dopt=Abstract

"A plain abdominal X-ray [Figure - 1] was advised that showed a linear radio-opaque shadow lying transversely in the pelvis. On persistent questioning, he gave a history of introduction of a 5.5 cm long aluminium rod"

http://www.jpgmonline.com/article.as...;aulast=Bakshi

I think that these are sufficient to show that even standard procedure X-Rays can render aluminum visible.

However, I will concede that there are also many links indicating that locating aluminum on X-Rays can be difficult in some cases. I think that would be a much more accurate way of stating your premise since it should be abundantly clear that saying it's invisible is overstating the problem.

July 4, 2006, 10:28 PM	#27
JohnKSa Staff Join Date: February 12, 2001 Location: DFW Area Posts: 24,971	"Exposure Level #1: X-rays can easily penetrate paper and cloth but can not penetrate denser materials such as rubber, glass, wood, or metals (aluminum, steel, and lead). " http://www.coe.uga.edu/mse/science/o...ys/x-rays.html "To block stray radio waves emitted by the detector's circuitry, the FPD was encased in a thin aluminum skin, which is almost transparent to x rays but opaque to radio. " http://www.aip.org/pt/vol-58/iss-6/p22.html "A typical X-ray will penetrate through thin layers of aluminum, and eventually be absorbed by the material." http://www.madsci.org/posts/archives...3690.Ph.r.html Quoting is hard since this is a pdf, but do a search on aluminum and find a very brief description on how aluminum is used to calibrate dental X-Rays by comparing it's known density on the images to other objects in the image. http://www.sciencenews.org/pages/pdf...9/15319-15.pdf "Calibration procedure of aluminum wedge by optical density gradient of its X-ray image " http://www.ncbi.nlm.nih.gov/entrez/q...&dopt=Abstract "Aluminum alloy wedges are used to standardize x-rays" http://lsda.jsc.nasa.gov/scripts/har...ardware_id=777 "Aluminum FB (foreign bodies) can often be visualized on radiographs" http://www.ncbi.nlm.nih.gov/entrez/q...&dopt=Abstract "A plain abdominal X-ray [Figure - 1] was advised that showed a linear radio-opaque shadow lying transversely in the pelvis. On persistent questioning, he gave a history of introduction of a 5.5 cm long aluminium rod" http://www.jpgmonline.com/article.as...;aulast=Bakshi I think that these are sufficient to show that even standard procedure X-Rays can render aluminum visible. However, I will concede that there are also many links indicating that locating aluminum on X-Rays can be difficult in some cases. I think that would be a much more accurate way of stating your premise since it should be abundantly clear that saying it's invisible is overstating the problem. __________________ Do you know about the TEXAS State Rifle Association?