What a single speck of dust does to scans

vbimport

#1

For the last couple of weeks my media seem to attract dust like crazy.

Several of my media have been burned with a single speck of dust attached to the surface, even though I’m careful to inspect disc surface before burning.

Today the evil dust speck had the good taste to wait until after the disc was burned before it attached itself, but still managed to do so in the few seconds it took to move the disc from the burning drive to the scanning drive.

Below you can see the difference in quality scans on the same disc before and after removing the single large speck of dust.

This is just for your information - I am not posting this to get your help, unless you want to come by and clean my apartment for free. :bigsmile:

[ol]
[li]Sum1 scan showing PIF with the dust speck still on the disc[/li][li]Sum1 scan showing PIF after the dust speck was removed[/li][li]PxScan with the dust speck still on the disc[/li][li]PxScan after the dust speck was removed[/li][/ol]I find the difference in scans quite educational.


#2

Burst scans for the same disc above, with and without the speck of dust.




#3

Looking at the scans above it also becomes apparent that the total number of PI Errors and the maximum PI Error value can vary quite a bit between scans on the same drive, but this isn’t really news I suppose?!


#4

Digging up this old thread because I recently re-explained the dust issue to a member encountering PIF clusters and not aware of the issue.

As during my routine re-scanning I encountered today a very relevant case, I though it would be nice to post it here. :slight_smile:

[B]1.[/B] Scan before dusting. Bif PIF cluster @~3.5GB. I examined the surface and found a speck of dust near the end of the burned area.
[B]2.[/B] Scan after dusting. No more PIF cluster. :cool:




#5

wow, thats dramatic, I need to rescan or dust off some disc and see how it goes


#6

A few years ago I had a NEC ND-2500 that would sometimes make contact with/scratch the disc during a burn; since then I just got in the habit of closely examining the surface of each disc before/after a burn and have been amazed by how much dust/small plastic chips can be on a brand new TY or Verbatim disc fresh out of the cakebox… :eek:


#7

I have had just this problem the other day, but with a new burn that got dust on it, you can see the tiny un burn spot of dye after I blew it off :sad: and there is quite a lot of building work going on here ATM and the dust is becoming a real pain.

Another, is a very small and light scratch scratch right near to the edge, I had seen it before and the plan was to do a 3.5 GB burn but I forgot :eek:



#8

We use swamp coolers (evaporative coolers) here in the desert, so dust gets everywhere. I started using canned air on my discs before I burn. I bought a bunch to get a decent bulk rate… kinda wish I hadn’t. That stuff goes a LONG way.


#9

I think I will have to get some, it just hurts to by a 'can ‘o air’, because I do have a compressor, but its in my garage… and just blowing on them does not work so well, as I expect I am not the only one that has sort of spat on my pre burn media :eek:


#10

Export the oversupply to Germany and be the first to offer them on competitive prices. :iagree:


#11

Another before/after dusting (I have many, many such scans :bigsmile: )
The PIF cluster @~3.3GB disappears. :cool:

Note: the difference in PIE levels isn’t due to the dusting but to the different scanning speeds. :wink:




#12

Yup. The second time that happened with a DL disc I ordered the cans. :iagree:


#13

I don’t like canned air, I dropped it entirely to dust my discs for two reasons:

  1. Obviously, the price.
  2. It actually has damaged some of my blanks when used before burning. I have no logical explanation why (I have some educated guesses) but it caused dye spots with consecutive generous PIF clusters.

I use an antistatic computer brush-like duster. Cheap, handy, very efficient. I posted an image of this stuff somewhere on the board but I can’t find it anymore. Oh but I found a page with the product, it’s the “[I]new duster 2001[/I]” model on this page: http://www.meidarlli.com.tw/E/body.php?web=11&FNo=101


#14

Dust is evil.

Francksoy: I guess it could be anything from the pressure of the air to perhaps moisture. I’ve never used canned air before, though. :wink:

Hrm about the brushes, could they possibly create scratches invisible to the eye? I suppose even specially designed wipes could cause minor scratches, though.


#15

Canned air causing “dye spots” could possibly be caused by very localized temperature differences on the disc, caused by liquid droplets or saturated vapor of the propellant. As the sprayed droplets or saturated vapor stream desperately try to complete their phase change to total vapor, they will rapidly absorb heat from any surface they make contact with – this disc in this case. (Ever wonder why the can gets cold after spraying a bit? It’s caused by a drop in internal pressure forcing more of the liquid propellant to flash to vapor, which then absorbs heat from the can and the hand holding it…)

Perhaps localized spots of momentary lower temperature than the rest of the disc can cause changes to the dye layer, enough so that the appearence changes, or it reacts differently to the write laser energy that is calibrated for the “normal” dye charactoristics of the rest of the disc?


#16

I would go with that 100%, the dye must have a range at which its reflectiveness will change …that is the way it works after all so I could see why it could ‘damage’ the disk/dye if it is ‘sent’ in the other way (cold).
I will be getting some next time I have an order, I think you just need to check what the propellant is (the older CFC nasty stuff was like this much more).

This is yet another way/reason why I am liking Verbatim media more and more, you cant wipe a burnt TY disk clean very well, I have supa soft cloths I used to knick from the body shop where I used to work and they will wipe Verbatim (i.e. normal) media clean and perfect …not TY.


#17

This was more or less one of my “educated guesses”. But you explain it extremely well, far better than I would have ever been able to. :clap:

If people are interested, I’ll try and find some of these discs and post pictures of the the issue (though I’m not 100% sure that I kept the discs)

Haven’t you noticed a difference between +R and -R TY? Here, it seems to me that the polycarbonate used with T02 is more resistant to scratches than the one used with TYG02. But overall, just like you, I much prefer MCC :wink:


#18

I have an old camera lens duster like the one shown below, that I though might be good for removing dust from CD/DVD media.

Wow was I wrong!
The brushes are only slightly less damaging than sandpaper on the polycarbonate surface of a blank DVD! :eek:

I’m glad I tested it on a coaster before actually using it on media that I need to keep.

You have been warned - don’t assume that a duster/brush intended for a different purpose will be good for cleaning CD/DVD media.


#19

eat some greasy french fries and handle a disk

I use the eyeglass cleaner with an old clean linen handkerchief carefully then lightly blow to remove any lint