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#1
Old 12-01-2001, 04:42 PM
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I was hangin late night at the Diner the other night with friends (having "late night at the Diner with friends"-type conversation) and something led me to quote an early episode of Seinfeld "You can't overdie, you can't overdry".

I'm not sure if anyone actually caught the reference, but I was challenged on the notion that you can't overdry clothes (we eventually specified clothes though I'm not sure of the implications for non-clothes items, or even if this would make a difference).

My friend claimed that clothes in their natural state always contain a certain bit of moisture and that if something was left in the dryer for long enough to remove all the moisture they may eventually catch fire. If I understand his point correctly (which I may very likely have not since we were a good few beers into the sunset) this would be considered overdrying.

But I'm thinking that if in fact the clothes did burn, this would be considered a diffent process than drying.
Or actually, maybe that wasn't the issue. I think I was actually saying that since drying can be defined as the removing of moisture, than once you've removed all moisture the object is dry. It can't get any dryer. So how can the notion of overdrying even have any meaning?

Actually, the more I think about it, the more I realize I don't even know what the heck I'm asking.

Can anyone help me understand the question?
#2
Old 12-01-2001, 06:57 PM
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It is possible to overdry. Most especially on the "high heat" setting. For example, lets just say you've purchased a length of green synthetic velvet with which to complete your costume design final. You wash it and pop it in the dryer for a few minutes because you want to get right to work. Except you get distracted for a minute, or 10. When you return, your fabric has not only dried, it has also melted in parts.

Cotton, if overdried, will be begin to burn -- not by dramatically catching fire, but by becoming over-stiff and "crispy" in texture.

I think you may have a mental block in understanding the dryer. Iit is NOT a dehumidifier (ie moisture-remover). Its only job is to generate heat, much like an oven. Imagine for a moment placing a t-shirt in the oven. You can imagine it burning if it gets too hot, right? Kinda ike toast left in too long? Same thing in a dryer.
#3
Old 12-01-2001, 07:02 PM
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Many natural substances contain water that cannot practically be removed without permanent damage, so yes, I'd say that for natural fabrics, it would be possible to overdry.

Leather, for example could become brittle and flaky if overdried.

The moisture content of wool is part of the reason that it is flame-resistant.
#4
Old 12-01-2001, 07:04 PM
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(not that I'm imagining for one moment that you'd put leather in a dryer - it was an illustration).
#5
Old 12-01-2001, 08:54 PM
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My mommy always cautioned me against overdrying clothes. I guess being exposed to that extra heat is bad for the fibers, especially over the course of many over-dryings.

Fortunately, my dryer has a moisture sensor on it, so it shuts itself off when the clothes are dry. Gotta love modern technology.
#6
Old 12-01-2001, 10:14 PM
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As someone who's depended on laundromats for the last ten years, I can promise you it's possible to overdry, as described above. In addition, overdrying wears out elastic. Nothing quite like having your underwear slippin' and slidin' and bunchin' up under yer cloze an' all, y'know? Or the ever-attractive sagging dress socks that expose your furry legs at inopportune moments.
#7
Old 12-01-2001, 11:53 PM
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The physics of it...

If something is wet, then the hottest it can get is 100C (212F).

Let's say you have 100 grams of water at room temperature, and add heat at the rate of 1000 calories per minute. The water will heat up 10 degrees per minute (1000/100) until it gets to 100C, which will take about eight minutes. At that point, the heat won't raise its temperature any more, but the energy is used to vaporize it. Water has a very high "latent heat," meaning it takes a lot of heat to vaporize it. So after eight minutes you'll have 100 grams of water at 100C, but a half-hour later the water will still be at 100C, there will just be 50 grams of it left. It took 27,000 calories to vaporize half the water. Another half-hour (for a total of 62 minutes), the water will finally all be vaporized.

If this is your shirt, then after the water is all gone, it's free to heat up to however hot the incoming air is, which is much higher than 100C. I would imagine that this would be harmful to most fabrics.
#8
Old 12-02-2001, 12:32 AM
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A sure sign that you've overdried is when you open the dryer and the clothes have all disappeared, but the lint filter has a giant brick of lint clogged onto it.
#9
Old 12-02-2001, 12:56 AM
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It's certainly possible to overHEAT clothes. Especially clothes with temerature sensitive components, such as elastic. But overDRY? If we're talking about natural gas dryers (as opposed to electric), they blow the exhaust (combustion products) of the gas fire directly through the clothes. And one of the primary components of natural gas combustion is water (albeit very hot water vapor).
#10
Old 12-02-2001, 03:44 PM
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So what IS overdrying/heating? I always throw my clothes (mostly cotton) into the dryer and put it on high for 70 mins. How close am I getting to making toast out of my undies?
#11
Old 12-02-2001, 04:43 PM
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Assuming your dryer isn't one of the nicer moisture-sensing ones, try this: if your clothes are hot to the touch when the cycle's done, they're overdry. Yeah, I know, that means you have to actually be at the dryer when the cycle's over, but it's worth it to have your clothes last longer.

I'm a fussbudget, so I actually check the dryer several times during the cycle and pull out the lighter fabrics as they finish. But that's me .
#12
Old 12-02-2001, 11:26 PM
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I once had a service wash at a laundromat over-dry my clothes. That is, leave them far too long in a tumble dryer on high. It was awful.

My shirts had what seemed to be scorch marks round the collar and shoulders, and everything smelled kind of cooked.

I figured out that some of the marks were due to deposits of oil from my skin, that hadn't been completely removed by the detergents, and that these deposits had essentially "fried" the material through overheating.

No, this is not a joke.

Some of the shirt buttons were all melted and unusable. Some fabrics were rippled and ropey-feeling. There was an unsatisfying kerfuffle wiht the laundromat owner - I just couldn't face the hassle of going to a small claims tribunal.

I thought it was all ruined, but months later, out of casual interest, I washed everything again, and some of the stains were reduced. I think one shirt and one pair of pants were salvagable, after a couple more washes.

Redboss
#13
Old 12-03-2001, 08:03 AM
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Yes, it's possible to overdry clothes, particularly cotton, where overdrying garments can ruin them through permanent shrinkage. Silk, wool and even linen are also susceptible to overdrying.
#14
Old 12-03-2001, 05:23 PM
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OK, so it seems I am in the wrong (as was Jerry Seinfeld).

I guess the distinction would be made according to whether or not a fabric exposed to constant heat (as in a mechanical dryer) would be damaged before or after all the moisture had been removed. IE if damage would not occur until after, then it could no longer be said to be a process of overdrying, but rather of overheating; but if damage occurs as a direct result of removing the moisture, well then I probably owe someone a beer
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