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DPChallenge Forums >> Hardware and Software >> Clouded glass on a flatbad a scanner - why?
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Showing posts 1 - 19 of 19, (reverse)
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 05/06/2007 01:28:23 PM · #1
I'm saving for an Epson 4990, but, in the meantime, I have to make due with a pretty crappy scanner in an HP PSC scanner-printer combo. But it's not the scan quality that is my primarily concern with my current scanner.

The inside of the glass was clouded. I managed to open up the scanner (although it is not meant to be user-serviceable) and cleaned the glass thoroughly. To my great surprise, the clouding re-instated itself in just a day after the glass was cleaned.

My current hypothesis is that the clouding is a result of condensation: the lamp heats the air inside the scanner, which causes slight condensation on the surface of the cold glass.

I have just opened it up and cleaned the inside of the glass for the second time. This time I put a few silica gel desiccant into the scanner's chamber. I'm hoping that drier air inside the scanner may help.

Has anyone else seen this? Any ideas?
 05/06/2007 01:29:50 PM · #2
Could try and put a few very small holes in the scanner somewhere, like in the plastic casing or something, just so the water can get out.
 05/06/2007 01:41:05 PM · #3
can someone point me i the direction of buying some of the "sillica gel"?
 05/06/2007 01:43:22 PM · #4
Originally posted by Jib:
can someone point me i the direction of buying some of the "sillica gel"?


Go to a shoe store and get those little packets from the shoe boxes.
 05/06/2007 01:48:27 PM · #5
you should be able to get the sillica gel at a craft store. some people use it to dry flowers.
 05/06/2007 01:51:34 PM · #6
Originally posted by Jib:
can someone point me i the direction of buying some of the "sillica gel"?

They are usually found in packaging of electronic equipment, shoes, etc. I usually save them, so I didn't need to buy. (Note - you need to "recharge" them before they become useful; putting them into an oven at above 100 degrees Centigrade for half an hour is supposed to renew them expelling accumulated water.) If you can't find any, I see that you can buy them really cheaply on eBay.
 05/06/2007 01:54:12 PM · #7
Originally posted by Ben:
Could try and put a few very small holes in the scanner somewhere, like in the plastic casing or something, just so the water can get out.

Won't it also work in the other direction - humid air getting in through the holes?
 05/06/2007 02:39:31 PM · #8
I don't think it's water condensation. As a matter of fact, it's nearly impossible, unless your room temperature is below the dew point, in which case there would be water condensing everywhere... walls, furniture, floors, etcetera.
What's more likely happening is that heat from the electronics is evaporating some higher-boiling material and that is redepositing on the glass. It does not take much material at all to cause a haze. I've seen this happen in industrial optics applications (bar-code readers). There's no easy solution unless you can pinpoint and remove the source of the evaporating material. That may prove difficult. It may be much easier to keep cleaning the glass.

Message edited by author 2007-05-06 14:39:45.
 05/06/2007 03:11:13 PM · #9
Does anyone smoke in the house? When I was younger, my parents smoked inside, and the scanner glass became very clouded. I've never had the problem since I've left the house for college.
 05/06/2007 04:36:21 PM · #10
Originally posted by kirbic:
What's more likely happening is that heat from the electronics is evaporating some higher-boiling material and that is redepositing on the glass. It does not take much material at all to cause a haze. I've seen this happen in industrial optics applications (bar-code readers). There's no easy solution unless you can pinpoint and remove the source of the evaporating material. That may prove difficult. It may be much easier to keep cleaning the glass.

I think you are right about the dew point...

If it's not water condensating, I find it hard to believe that it evaporates quantities enough to form residue in just one day after cleaning. Hmm...
 05/06/2007 04:37:09 PM · #11
Originally posted by C_A_Morris:
Does anyone smoke in the house? When I was younger, my parents smoked inside, and the scanner glass became very clouded. I've never had the problem since I've left the house for college.

No, I and my wife are both non-smokers.
 05/06/2007 04:56:42 PM · #12
Originally posted by kirbic:
I don't think it's water condensation. As a matter of fact, it's nearly impossible, unless your room temperature is below the dew point, in which case there would be water condensing everywhere... walls, furniture, floors, etcetera.

After a second thought, doesn't dew point depend on the *air temperature*, as well as humidity? It seems to me that the warmer the air, the higher the dew point. If so, then it would be possible that the lamp heated up the air inside the scanner to the point at which the room temperature would be lower than dew point, no?
 05/06/2007 05:06:38 PM · #13
Originally posted by agenkin:
Originally posted by kirbic:
I don't think it's water condensation. As a matter of fact, it's nearly impossible, unless your room temperature is below the dew point, in which case there would be water condensing everywhere... walls, furniture, floors, etcetera.

After a second thought, doesn't dew point depend on the *air temperature*, as well as humidity? It seems to me that the warmer the air, the higher the dew point. If so, then it would be possible that the lamp heated up the air inside the scanner to the point at which the room temperature would be lower than dew point, no?


Nope... some facts:

- If you take a volume of air with a given amount of moisture and heat it, the dew point remains the same.
- If you measure the relative humidity of the above air at the lower and higher temperature, you'll find that the relative humidity has dropped at the higher temperature.

The above are true because air holds more moisture at higher temperatures, and the relative humidity is just a number that describes how much moisture is present compared to the maximum possible (that's why it's a percentage). Dew point is jut the temperature at which the humidity is 100%, for the current amount of moisture dissolved in the air. Typical indoor relative humidities are <70%, and dew points are thus more than 10 degrees F below room temperature.
So, back to your situation... if the humidity inside the scanner is high, and the electronics heats the air in the scanner, the humidity inside the scanner drops. Further, the hottest air will rise to the top of the enclosure, making the glass hotter than the bottom surface. No condensation will ever form there with the unit on.
If, however, there is some heat source that is evaporating a substance that has a relatively high boiling point and low solubility in air, the glass could very well be providing a cool surface on which the material is being deposited.

Message edited by author 2007-05-06 17:08:53.
 05/06/2007 05:11:50 PM · #14
Plastics give off 'fumes' as they age & decompose. My mom is into collecting things and there are preferred methods of storage. I know that the cheap plastic boxes that you can buy at most any dept or discount store (Walmart Target) are a big no no for keeping collectible items in since their plastcs give off fumes and can ruin the item you are storing. Using this info it is very possible that your old flatbed scanner's plastic parts have reached an age where the fumes are more than they used to be and might be what is clouding your glass so quickly.

05/06/2007 10:08:02 PM · #15
Sounds to me like your printer / scanner combo isn't long for this world. Failing electrolytic capacitors in the power supply start to vent and are the likely cause of the substance Kirbic is suspecting. This form of gradual demise is one of, if not the, most common failure mode for modern mains powered electronic devices. One day soon it will fail to power-up altogether, it'll probably tick a bit but thats it.

I could also be completely wrong!
Mike
 05/06/2007 10:14:28 PM · #16
I had a similar problem with my scanner and I also had the lines going through the clouding. This started coming up on anything I scanned. I managed to pull the scanner apart (it was also not very service friendly, but I am good at pulling things apart) and I cleaned the galss with a water/metho solution and managed to put the whole thing back together again. I haven't had it come back again and it's been probably about 8 months. My scanner is about 2 1/2 years old.
 05/06/2007 11:07:53 PM · #17

You might try cleaning the glass with comet, clear viniger or something like that. Sometimes glass cleaner will leave a film on glass. I use comet to clean the glass I fuse with and it comes out very clean.

If your scanner does die, save the glass. The glass is low lead glass and optically clear without the tint you see in regular window glass. It's great for doing things with that needs clear glass. I was looking for some when I made a water tank to do photography with. I wanted to put the low lead glass as the front glass (the others would have been regular glass) so I could get a better image through it. Glass in flat bed scanners and copiers are made with low lead glass and it can usually be gotten for free when people throw them out.

Mike
 05/07/2007 10:26:57 AM · #18
I have had the same problem, did the same thing as you and still have the problem days after just like you.... There is Ink in that printer and I am wondering if the ink is the cause. HP Sucks anyway. I warned wifie!

As being trained to service HP injets (nobody trained outside HP service in over 15 years), I can tell you that I will never buy one again. The one I now have is because my wife is thick and did not want to listen. The ink fades in light QUICKLY, the print quality sucks, the cartridges are a huge expence per page because you never get the full amount out of the cartriges and I have owned 4 HPS in 3 years and then replaced it with an Epson that worked for over 7 years...then I gave it to my friend who uses it today....7 years later!!!!!! BUY a scanner separtate, and get an epson or canon printer....UNLESS you are looking for a laser, then HP is still the way to go.

P.S. I am HP Inkjet, laser trained and trained in printers such as
Oki's
Lexmark
Panasonic
IBM
and others

my $.02
 05/07/2007 10:31:01 AM · #19
Originally posted by zardoz:
Sounds to me like your printer / scanner combo isn't long for this world. Failing electrolytic capacitors in the power supply start to vent and are the likely cause of the substance Kirbic is suspecting. This form of gradual demise is one of, if not the, most common failure mode for modern mains powered electronic devices. One day soon it will fail to power-up altogether, it'll probably tick a bit but thats it.

I could also be completely wrong!
Mike


I think you are wrong...ONLY because I cleaned my wifes printer 2 times in the past 3 years, still working like the little choo choo that thought he can. I hate that piece a crap! Try to make a T-Shirt with an HP and an Epson....THEN WASH IT, you will understand! ;)
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