Normally, I do posts reviewing products, random thoughts or experimenting with things. But this time, this is probably one of my first cautionary articles based on what just happened to me.
On 25th December 2013, about a year ago, I ordered twenty TDK premium BD-R DL 4x discs for a backup burn session. These discs came from a Japanese eBay seller, being packed in sleeves as seems to be a common arrangement.
I really dislike the sleeve “repackaging” operation as sleeves can introduce some dust onto the disc surfaces, which can affect burn and test quality. Regardless, this was what was on offer, so I reluctantly accepted.
The discs had media identification code of TDKBLD-RFB-000. About 14 of the discs were used within the first month of receiving them, and burned with reasonable quality and no failures. This left me six discs in spare, which I decided to hold until they were actually needed.
Unfortunately, room in my “room” is relatively limited, and things quickly become buried under a pile of stuff. In the case of these discs, they remained in their sleeves with a 100-pack spindle and a jewel case sitting on top of them for about 10 months or so.
What the Hell?
I then had a project which required a BD-R DL disc, and satisfied that I had some good blanks left over, I grabbed one and put it into my favourite Pioneer BDR-209DBK and fired up the trusty Imgburn. It choked at identifying the disc for a while, and then came up with Incompatible Medium Installed. Only two of the remaining discs were detected by the Pioneer, but the burns failed with problems with servo tracking.
I swear the discs are compatible, so I took it out and examined the bottom surface. There was some evidence of potential outgassing or chemical reaction of the sleeve liner material with the bottom surface, creating a spotty pattern on the bottom of the disc. A good run with a microfibre cloth and high purity isopropyl alcohol removed the pattern, however, the drive continued to dislike the disc altogether.
As the burner was the newest one in my fleet, I was skeptical that it was actually a problem, so I resorted to “trusty-ol” LG GGW-H20L 6x Supermultiblue burner. Putting the disc in resulted in a moderately long detection time, and this time, the blank was correctly identified.
But the burning process was problematic. Of four discs attempted, one disc never started despite given eight hours – being stuck in a spin-up and down loop at Reserving Track. The others took 10-30 minutes to clear reserving track, and two of them failed mid burn with Servo Following Error/Invalid Address for Write. The only one that wrote correctly failed verification at 10% on the first layer with read error. Some of the discs were burnt at 4x selection, others at 2x selection, with failures at both settings.
The discs were totally screwed. Issues with the burners have been eliminated – they both showed the same issues and had no issues with burning single layer media.
Post Mortem and Hypothesis
Taking a look at the discs I had kept (others destroyed out of rage) gives a bit of an idea of just how hard the drive tried to get a write.
This burn errored out in a short time, but clearly has a thick band near the centre of the hub which is the power calibration area. It implies the drive spent a lot of time trying to tune the laser power to make the written data readable, much more than reasonably expected on a good disc.
The disc that burnt further exhibits strange “variations” in burn beta (darkness), best seen when examining the full size image by clicking. Patches of the media seem to remain unburnt as if the media response is uneven – possibly related to where more pressure was applied to the disc surface by the slightly ridged pattern of the sleeves.
The discs that were not stored for significant periods, or under much physical pressure, burnt fine the first time with no recording quality abnormalities even within this same batch. It is likely the storage conditions or the storage time itself could have caused the issue.
My hypothesis based on this observation is that the weight pressure placed on the discs may have interfered with the definition of the two layers on the disc and may have “compressed” them unevenly, damaging their very closely specified separation and making focusing on each layer difficult to impossible. The separator between layers may have been punctured by the weight pressure causing the media to be less sensitive to laser at those points, or be de-focussed and not actually burn the media correctly.
I suppose all of this is my fault for carelessly stacking things upon blank BluRay discs, but it definitely deserves a mention in case someone else might have experienced this. In all, sleeves seem to be a suboptimal storage solution because of the outgassing causing patterns to be remnant on the disc surface which can affect burn quality significantly, and the ridged pattern being impressed into the disc under pressure can affect the recording coat.
I have no idea if discs stored under compressive strain (stacked in tall stack in sleeves) are affected if they are already burnt, but it appears that it pays benefit to exercise caution.
It was a pretty expensive lesson after all with six BD-R DL discs lost … but maybe if the discs were left for a few weeks without compressive force on them, their layers might return to a better definition? I’m not sure, but I don’t have any more of the bad discs to test the theory on.