I need input from those more technically adept than I. This is not a subject you can learn through experience.

Assume you can achieve one or the other but not both.

Low humidity!
Especially if the disc does not have any lacquer on the edges.

chas0039, I'm confused by your poll.

The title of the thread seems to indicate that we should vote and post for which condition is worse for a disc, but the way you phrase the poll question indicates that you want to know which is better for a disc.

So which is it?

Hi Chas

It probably depends on the chemical characteristics of the discs, but I think it's mostly air humidity (not water! - inputting this for people claiming that air humidity is not a problem because they can soak discs in water with no degradation ) that is the biggest risk.

Air humidity can penetrate the polycarbonate and bring contaminants in the dye, and cause corrosion of the reflective layer. Not couting moulds, that seem to be able to grow anywhere.

Heat accelerates chemical activity. Heat could also impact the glues (bonding) or the tilt (=> causing warping of the disc), but I don't think such impact would appear unless the discs reaches at least 50 °C (direct sunlight). I'm also interested in reading input from people "more technically adept than I". about this.

Now it would be important to be more precise about what is referred to as "too high" air humidity and/or "too high" temperature. Maxell, Memorex and Verbatim have clear recommentations. I think anything < 30 °C and < 65% relative humidity should be considered as safe. But as mention is my first paragraph, it can depend on the chemical and mechanical characteristics of each MID...

And as you probably already know, each factor has a huge influence on the other, which complicates things drastically. Humidity is more "active" when the air is hot, and heat is more "active" when the air is damp...

Maybe a more precise, concrete example could find a better reply...

I've also been confused at first. I think it would be nice to change the title of the thread, DrageMester (If Chas0039 agrees, of course).

Tricky tricky tricky.

Higher heat has 2 disadavantages.
At higher heat reaction rate increases.
At higher rate humidity increases. (more water)

iThe next question is what is HIGH ?
Any idea of ranges we are comparing ??

Yup, exactly, what do you mean when you say high humidity, low humidity, high heat and low heat? Is 29-31C high heat and 60-70% high humidity? I'm asking because those are the conditions my discs live under. If that is what you mean then I may be able to answer from personal experience rather than conjecture.

Go ahead and change the title if you wish. Neither is good so a vote in the poll is for the environment which is least bad. I could have worded the poll to make a vote for the worst situation but that made no sense either.

Also, for my situation, assume high humidity situation is 50% humidity and 70F temp. Assume high temp situation is 35% humidity and 85F.

Thanks for all the input guys. Looks like I need to make a move for storage.

i agree with your comments, it is confusing the way he worded it ... but if u asked me what i think is "best" for the disc i would obviously say "low humidity".

note: i dont consider myself a expert or anything but this is just what i would think in general of what would be overall worse for a disc on average peoples conditions since most peoples discs wont never be in direct sunlight thats why i would say that humidity would seem worse for the disc than higher heat... i live in michigan usa so theres only about 3months or so thats fairly humid and my house has central air (air conditioning) but in my room where pretty much all my cd's-dvd's are stored is pretty much the hottest/highest humidity room in the house... durring summer i would say my room is roughly around 80f at a fairly high humidity (dont know exactly how high but this is just a rough estimate)

just my thoughts... im sure theres someone on here that knows what there talking about .

Keep in mind that your probably measuring Relative Humidity!!
HIgher temperature means that more water can be there are the same Relative humidity.

Yes, which makes the whole thing more complicated than it seems.
Though, if a dehumidifier is used to keep the relative humidity under reasonable values (< 60%, or better < 50%), it will automatically adapt to the changes in temp (via the change induced in relative humidity)

I am glad to find you guys are having trouble with this one as well. I have been pondering this all Summer as the humidity increased and it went back and forth.

Why not get practical instead of theoritical on this one?

I know you use almost exclusively YUDEN00T02 and MCC004. So it's easy for you to check the resistance of your discs to these humidity variations. A sample of 10-15 discs of each MID from different batches, re-scanned after a year or so, should be enough to ease your mind. From my own experience I find these two MIDs to be very good for climatic stability.

If you find no significant changes in error figures after a year despite the changes in heat/humidity, I don't think you should worry unless you start, in the future, storing discs in a damp wine cave... (which I'm pretty sure you will not do )

I have already tested some discs from both settings and after 2 years there is no difference... as in almost identical scans. I don't think the environment will become a factor in my situation for quite a few years, at which time it will be too late.

And you are very right... I don't even have wine in a wine cave.

It's normal that you see it fluctuating during the summer.

Now to get to a better answer. Based on your results. Let me try to do some reasonable thinking to come to a reasonable conclusion.

Let's assume that the actuall humidity(water concentration in air) stays the same. Which isn't that unlikely.
During summer you see relative humidity dropping when your temperature gets higher.

I think the Higher temperature becomes the worse scenario.
Your concentration of water is still the same (only reported lower as relative humidity because air can now hold more water)
Based on thermodynamics the reaction rate will be faster with higher temperature.So faster degradation.

There is one thing. In case of Degradation for most media I think mass transfer is more important as kinetics. So the actuall degradation will be based on how much of this water/air mixture can get to the media to oxidize it. Now to get there it has to go through the polycarbonate which ain't easy or through the bonding layer which is also not easy.
However with a bad bonded disc. Things become much more easy.

So in your situation of your room. Higher temperature is worse !

Note this is based when comparing relative humidity and temperature !
Incase of absolute temperature.

But since the question speaks of Humidity and not relative humidity I won't vote because things become more tricky as stated with the original formulated question !

Also, if I read you right, you assume the same humidity in the summer and just a change in temp. Actually, I am looking at the second floor of a house where the temps are on the high side or a landing on the way to the basement where the temps are much lower. Given the proximity to the basement, the humidity is significantly higher than what would be expected if I just lowered the temp to match in the room upstairs. So I think the impact of the humidity is much worse than in your scenario.

High humidity raises the heat index so i went with high heat low humidity. But on another note i think UV light/sunlight is more apt to do damage than high humidity or 100 degree temps. JMO.

YEp cellars and basement are most times more humidit places. So my easy situation of same room is no longer valid.
Which means we're back at the question as earlier formulated.


And yes UV can do much more damage. Some disc's when put in the sun will beceme unreadable after one or 2 days !

In both cases the discs are in total darkness so UV is not an issue. It is down to humidity or heat.