| Author |
Message |
Michael C
science forum beginner
Joined: 19 May 2005
Posts: 11
|
 Posted: Thu May 19, 2005 1:46 am Post subject:
Disolve plastic
|
|
|
I'm looking for something to etch the surface of an LED so that it becomes
more diffuse. Sanding worked very well but wasn't even enough, causing the
light output to look patchy. I'm looking for something that can do the same
thing chemically. I'm not a chemist so something that is widely available
would be preferable. I've asked in a couple of non-chemist groups and
haven't got an answer so my apologies for the double post.
Many thanks,
Michael |
|
| Back to top |
|
 |
Wilco Oelen
science forum beginner
Joined: 25 Mar 2005
Posts: 33
|
| Posted: Thu May 19, 2005 4:28 am Post subject:
Re: Disolve plastic
|
|
|
Michael C schreef:
| Quote: | I'm looking for something to etch the surface of an LED so that it
becomes
more diffuse. Sanding worked very well but wasn't even enough,
causing the
light output to look patchy. I'm looking for something that can do
the same
thing chemically. I'm not a chemist so something that is widely
available
would be preferable. I've asked in a couple of non-chemist groups and
haven't got an answer so my apologies for the double post.
Many thanks,
Michael
|
If the LED head is made of glass (and many times this is the case),
then there will not be anything capable of etching this, which is
available easily and without risk.
Glass can be etched and made more diffuse by keeping it in moist
hydrogen fluoride (hydrofluoric acid) fumes, but this definitely is not
something you should do in your kitchen! Instead of hydrofluoric acid
you can use sodium fluoride, added to concentrated muriatic acid. The
chemicals for this are much less dangerous on storage (although
concentrated muriatic acid is no children's toy either), but the
etching act still is quite risky. Hydrofluoric acid is REALLY REALLY
bad for you, your skin and almost all materials around you!
If the LED head is made of plastic, then you could try to dip the LED
head in some acetone. Acetone attacks many plastics, but not all of
them. Just give it a try. Acetone is easily available, not expensive
and relatively non-toxic. It is very flammable!
As a last resort you could try to place a piece of white/milky plastic
over the LED head or in front of the LED head. What about carefully
taking apart a small diffuse tungsten light bulb (e.g. from
christmas-light) and putting the LED inside the small glass sphere?
Wilco |
|
| Back to top |
|
|
N:dlzc D:aol T:com (dlzc)
science forum Guru
Joined: 25 Mar 2005
Posts: 2835
|
| Posted: Thu May 19, 2005 11:11 am Post subject:
Re: Disolve plastic
|
|
|
Dear Wilco Oelen:
"Wilco Oelen" <photo@woelen.nl> wrote in message
news:1116484128.070792.228900@g44g2000cwa.googlegroups.com...
....
| Quote: | Glass can be etched and made more diffuse
by keeping it in moist hydrogen fluoride
(hydrofluoric acid) fumes, but this definitely is
not something you should do in your kitchen!
Instead of hydrofluoric acid you can use
sodium fluoride, added to concentrated
muriatic acid. The chemicals for this are much
less dangerous on storage (although
concentrated muriatic acid is no children's
toy either), but the etching act still is quite
risky. Hydrofluoric acid is REALLY REALLY
bad for you, your skin and almost all
materials around you!
|
.... and then you have to dispose of the waste. Some sort of
calcium compound perhaps? Chicken bones or some such, to attract
and "inactivate" the fluorine?
David A. Smith |
|
| Back to top |
|
|
Martin Brown
science forum addict
Joined: 12 May 2005
Posts: 82
|
| Posted: Thu May 19, 2005 11:59 am Post subject:
Re: Disolve plastic
|
|
|
Wilco Oelen wrote:
| Quote: | Michael C schreef:
I'm looking for something to etch the surface of an LED so that it
becomes
more diffuse. Sanding worked very well but wasn't even enough,
causing the
light output to look patchy.
If the LED head is made of glass (and many times this is the case),
then there will not be anything capable of etching this, which is
available easily and without risk.
|
I can't recall ever seeing a normal LED glass encapsulated. They are
usually set in a clear or coloured relatively soft plastic.
HF glass etching is certainly not safe for a non-chemist. And will be
completely ineffective against most plastics anyway.
| Quote: | If the LED head is made of plastic, then you could try to dip the LED
head in some acetone. Acetone attacks many plastics, but not all of
them. Just give it a try. Acetone is easily available, not expensive
and relatively non-toxic. It is very flammable!
|
He is probably better off finding some carborundum grinding powder and
using that to obtain an even rough surface finish. It should be possible
to get a decent even matt surface finish with 600 grit or finer.
Regards,
Martin Brown |
|
| Back to top |
|
|
Uncle Al
science forum Guru
Joined: 24 Mar 2005
Posts: 1226
|
| Posted: Thu May 19, 2005 2:29 pm Post subject:
Re: Disolve plastic
|
|
|
Michael C wrote:
| Quote: |
I'm looking for something to etch the surface of an LED so that it becomes
more diffuse. Sanding worked very well but wasn't even enough, causing the
light output to look patchy. I'm looking for something that can do the same
thing chemically. I'm not a chemist so something that is widely available
would be preferable. I've asked in a couple of non-chemist groups and
haven't got an answer so my apologies for the double post.
|
Tumble with somewhat coarse grit. Grit size couples to frosting
fineness. Plastic is a no-brainer. Glass will do better with
carburundum or alumina. Rotate on a spindle and sand blast if you a
are in a hurry, or dip the spinning LED into a porridge of abrasive.
Why don't you buy a diffusive LED? They come clear and cloudy.
Glass will etch and frost in gaseous HF. HF is tremendously toxic.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz.pdf |
|
| Back to top |
|
|
Michael C
science forum beginner
Joined: 19 May 2005
Posts: 11
|
| Posted: Thu May 19, 2005 8:15 pm Post subject:
Re: Disolve plastic
|
|
|
"Uncle Al" <UncleAl0@hate.spam.net> wrote in message
news:428CBEF2.496F8A33@hate.spam.net...
| Quote: | Why don't you buy a diffusive LED? They come clear and cloudy.
|
I can't find a diffuse high brightness LED in 10mm, if I could a would. They
probably exist but none of the suppliers I know of have them.
Michael |
|
| Back to top |
|
|
Uncle Al
science forum Guru
Joined: 24 Mar 2005
Posts: 1226
|
| Posted: Thu May 19, 2005 10:39 pm Post subject:
Re: Disolve plastic
|
|
|
Michael C wrote:
| Quote: |
"Uncle Al" <UncleAl0@hate.spam.net> wrote in message
news:428CBEF2.496F8A33@hate.spam.net...
Why don't you buy a diffusive LED? They come clear and cloudy.
I can't find a diffuse high brightness LED in 10mm, if I could a would. They
probably exist but none of the suppliers I know of have them.
|
Chuck it, spin it up, run some fine sandpaper from tip to edge.
Carbide sandpaper if it is a glass LED.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz.pdf |
|
| Back to top |
|
|
Michael C
science forum beginner
Joined: 19 May 2005
Posts: 11
|
| Posted: Thu May 19, 2005 10:57 pm Post subject:
Re: Disolve plastic
|
|
|
"Uncle Al" <UncleAl0@hate.spam.net> wrote in message
news:428D31B4.F4F5519A@hate.spam.net...
| Quote: | Chuck it, spin it up, run some fine sandpaper from tip to edge.
Carbide sandpaper if it is a glass LED.
|
That's a good idea, I could even do it with a drill in a vice.
Michael |
|
| Back to top |
|
|
N:dlzc D:aol T:com (dlzc)
science forum Guru
Joined: 25 Mar 2005
Posts: 2835
|
| Posted: Fri May 20, 2005 2:19 am Post subject:
Re: Disolve plastic
|
|
|
Dear Michael C:
"Michael C" <me@nospam.com> wrote in message
news:428d0fee$0$79454$14726298@news.sunsite.dk...
| Quote: | "Uncle Al" <UncleAl0@hate.spam.net> wrote in message
news:428CBEF2.496F8A33@hate.spam.net...
Why don't you buy a diffusive LED? They come clear
and cloudy.
I can't find a diffuse high brightness LED in 10mm,
if I could a would. They probably exist but none of
the suppliers I know of have them.
|
Diffuse light sources divert some of their energy back into the
source, usually as heat. This will shorten the life of the
device. You might want to discuss your requirements with a
knowledgeable representative of one of the companies.
David A. Smith |
|
| Back to top |
|
|
Martin Brown
science forum addict
Joined: 12 May 2005
Posts: 82
|
| Posted: Fri May 20, 2005 5:15 am Post subject:
Re: Disolve plastic
|
|
|
Michael C wrote:
| Quote: | "Uncle Al" <UncleAl0@hate.spam.net> wrote in message
news:428CBEF2.496F8A33@hate.spam.net...
Why don't you buy a diffusive LED? They come clear and cloudy.
I can't find a diffuse high brightness LED in 10mm, if I could a would. They
probably exist but none of the suppliers I know of have them.
|
They are usually packaged in what I think is water clear acrylic. Most
electronics sites just say "plastic". eg
http://www.electronicsweekly.com/Article39329.htm
Regards,
Martin Brown |
|
| Back to top |
|
|
Wilco Oelen
science forum beginner
Joined: 25 Mar 2005
Posts: 33
|
| Posted: Fri May 20, 2005 6:46 am Post subject:
Re: Disolve plastic
|
|
|
Martin Brown schreef:
| Quote: | Wilco Oelen wrote:
Michael C schreef:
I'm looking for something to etch the surface of an LED so that it
becomes
more diffuse. Sanding worked very well but wasn't even enough,
causing the
light output to look patchy.
If the LED head is made of glass (and many times this is the case),
then there will not be anything capable of etching this, which is
available easily and without risk.
I can't recall ever seeing a normal LED glass encapsulated. They are
usually set in a clear or coloured relatively soft plastic.
Depends... The small ones, used in some stereo sets and the like as |
indicator LEDs, indeed are encapsulated in a colored plastic head, but
the larger high efficiency LEDs almost all have a crystal clear
colorless glass head (I have a few of these things at home which emit
very bright red light). You can easily see the "circuitry" under the
glass in these LEDs. Nowadays you can also buy very bright white-light
or blue-light LEDs and these also have a colorless glass head.
| Quote: |
HF glass etching is certainly not safe for a non-chemist. And will be
completely ineffective against most plastics anyway.
I agree.
If the LED head is made of plastic, then you could try to dip the
LED
head in some acetone. Acetone attacks many plastics, but not all of
them. Just give it a try. Acetone is easily available, not
expensive
and relatively non-toxic. It is very flammable!
He is probably better off finding some carborundum grinding powder
and
using that to obtain an even rough surface finish. It should be
possible
to get a decent even matt surface finish with 600 grit or finer.
If the powder is sufficiently fine, yes.
Regards,
Martin Brown |
|
|
| Back to top |
|
|
Google
|
|
| Back to top |
|
|
|
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
Forum index
»
Science and Technology
»
Chem
