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Does fluorescent light cause yellowing?

A

apple2fan

Experienced Member
Joined
Jul 24, 2006
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Location
United States, TX
Its been a while since I've been on here, this last year has been rough. but i have a question.
Does fluorescent light cause yellowing/discoloration? I've got an apple II right underneath a fluorescent lamp and I'm concerned if it could get yellowing on the case from it.
I know I've heard sunlight affects apple II's but i have a black curtain over the room window that i store my 2s in. Thanks.
 
You might consider using Incandescent lighting around something thats more vulnerable to yellowing than other things. Florescent lamps do emit shortwave UV light and any amount of UV light will cause yellowing over time but I don't know how much of it escapes the lamp.
 
Yea, i considered it. I never liked regular bulb light, it seams to dim.:(
This is similar to the light i have:
http://www.staples.com/webapp/wcs/stores/servlet/StaplesProductDisplay?zipCode=76248&jspStoreDir=Staples&catalogId=10051&productId=102248&cmArea=SEARCH&errorUrl=zipcode&ts=1208919259890&langId=-1&storeId=10001&cmSearchKeyword=Architect+Organizer+Fluorescent+Desk+Lamp
The light is only on occasionally, and the longest its been on is 1hr. not sure if this makes a difference though. Thanks for the info.
 
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I don't think a desk light is going to emit enough UV radiation to really worry about it. I'm guessing it'd take a higher dose to cause any actual damage.
 
Here in New Zealand I've never seen a yellowed Mac?? Either personally or our local auction site. How common are they? They often seem to come up on these forums.

I can think of three possible reasons...

1. I simply haven't seen enough old Macs. This is possible, although I have seen a few... those I've scrounged, those around the place I work, at the local recyclers and on our TradeMe site. None have been particularly yellowed.

2. Our light is lacking in UV. Definitely NOT a reason! We have some of the highest UV levels in the world, thanks to the ozone hole over the Antartic. I've have seen a number of machines here that definitely ARE yellowed, Amigas in particular.

3. Our Macs used a different type of plastic. Perhaps this is the answer? The Macs I have were all manufactured in Singapore. Is this true for Macs elsewhere. I imagine Macs in the US were manufactured in the US or perhaps Mexico? (is this correct?).

Anyway, it's an interesting observation. As I say, maybe I haven't seen enough of them.

Are yellowed Macs common in Australia?

Tez
 
Just did a little research, I don't think you need to worry about the plastics exposer to UV light, but do be careful of EPROMs. Over time there is enough emitted from a florescent light to gradually erase them so make sure the little quartz lens is covered or out of sight of the lamp. Black lights have a bad habit of doing this as well, only a little more so because they emit a different wavelength than regular florescent lamps.
 
Tezza-

There are such things as additives that block and absorb UV emissions but those are generally used in plastics and polymers that are used outdoors such as deck chairs and such. I don't think I've ever seen them used in computer cases but that doesn't mean it hasn't happened. They also degrade over time but they do substantially lengthen the life of whatever the product is. It would have been a good idea in hindsight but ah well. I don't think that kind of process had been perfected yet back then.
 
Just came across this interesting bit of info, apparently 8 hours of exposure to a typical florescent light bulb, like the tube ones used in halls and offices equals just over 1 minute of natural sunlight. So I highly doubt the plastic will be harmed by compact bulbs and or desk lights. I'd just make sure to cover any exposed EPROM chips.
 
I honestly wouldn't doubt fluorescent lighting causes yellowing. It definately does something! At my work, we store boxes high up near the ceiling. I've noticed that when I go pull the boxes down, the top box (which has been under the light) will be lighter than the rest of the boxes.

From what I've seen, heat is usually the big culprit when it comes to yellowing. Every computer printer / photocopier I see starts to yellow around the heat vent. IMO, if you want your computers to stay white, keep them away from heat, and you might want to mod the case with a cooling fan :)
 
Hi
Ozone is a factor as well. Places with more smog will
yellow things faster as well.
As for lamps, even though the lamps are slow compared
to sun light, they will yellow cases fast. It is just that
sun light will do it really fast. Often for home systems,
people will have their desk near a window. This increases
the yellowing a lot.
As for erasing EPROMs, it will take 10's of years to erase
with a florecent lamp at normal room distances. It takes
the shorter wave length of UV to erase. The longer wave
length has no effect but will still yellow plastics.
Dwight
 
Vlad said:
Just came across this interesting bit of info, apparently 8 hours of exposure to a typical florescent light bulb, like the tube ones used in halls and offices equals just over 1 minute of natural sunlight. So I highly doubt the plastic will be harmed by compact bulbs and or desk lights. I'd just make sure to cover any exposed EPROM chips.
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Thank you very much! Now I know it wil be safe. COOL!
 
From what I've seen, heat is usually the big culprit when it comes to yellowing.
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I agree. A guy I bought 1 of my IIe's from had his computer in his sweaty garage right in direct sunlight from a window. It was so yellowed a magic eraser didn’t even work!
Anyone else have these problems?
 
Several years ago I stored an Amiga 500 in a large wooden chest. At that time the A500 was in perfect condition. Last year when I pulled it out to have a look, I was shocked to see that it had badly yellowed. During the time it was in the box it was not exposed to any light, and the ambient temperature never went above 75 degrees F.

What's interesting though is that it was covered in what looked to be a layer of wood dust (I didn't seal the unit in a plastic bag). I wonder if that possibly had any effect on the yellowing. I have an A2000 and C128, and 1084 monitors roughly the same age that have not suffered any kind of yellowing.
 
Anonymous Coward said:
Several years ago I stored an Amiga 500 in a large wooden chest. At that time the A500 was in perfect condition. Last year when I pulled it out to have a look, I was shocked to see that it had badly yellowed. During the time it was in the box it was not exposed to any light, and the ambient temperature never went above 75 degrees F.

What's interesting though is that it was covered in what looked to be a layer of wood dust (I didn't seal the unit in a plastic bag). I wonder if that possibly had any effect on the yellowing. I have an A2000 and C128, and 1084 monitors roughly the same age that have not suffered any kind of yellowing.
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Hi
It is most likely vapors from the wood. In general, anything that
creates an oxidizing invironment will cause yellowing of most plastics.
Dwight
 
Some plastic bags will also react with different plastics. From understanding its a combination of heat, sunlight, mold release from manufacturing, and the resin used that affects the case yellowing. It is a chemical process that breaks down the plastic polymer releasing sulfer that makes it yellow (atleast if sulfer was used to cross link the polymer like they do with rubber).
 
Unknown_K said:
Some plastic bags will also react with different plastics. From understanding its a combination of heat, sunlight, mold release from manufacturing, and the resin used that affects the case yellowing. It is a chemical process that breaks down the plastic polymer releasing sulfer that makes it yellow (atleast if sulfer was used to cross link the polymer like they do with rubber).
Click to expand...

agreed
 
There should hardly be more than a trace of anything else than the main component polyethylene in a standard plastic bag, which is totally inert.
There might be some processing lubricants, but they do not contain anything else than esters (soap-like materials).

Flexible dust covers were frequently made of plasticized PVC. Over time, the plasticizers might migrate and could have an effect on the machine casings.
As for UV light, PVC is blocking that very well..

As for fluorescent lamps, yes, the mercury vapor inside emits ultraviolet light at 185 and 256 nm bands. The heavy metal based fluorescent powders (Yttrium oxide for the red component, for instance) that are coated on the inside of the glass tube absorb this and emit visible light.
Ofcourse, the manufacturer is looking for high conversion efficiency here.
Old tubes, or better old fluorescent powders, have about 50-70% efficiency.
Newer ones are above 95%.

So installing a newer one from a good brand might actually help.
If the tube its installed in a casing and behind glass, don't bother, UV will hardly pass that.

Most important: don't eat the tube..
 
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