Pillow case mystery

[zdas04]

Friction. With a feather pillow (or ground up foam) when you move in the night the friction between your skin and the pillowcase is much lower than the effective friction between the pillowcase and the pillow casing because the pillow filling tries to move with the pillow casing. With a near fluid inside the pillow casing the pillow case, casing, and fill tend to want to move as a system.

With the monolithic fillings, the friction between the filling and the casing is a similar magnitude to the friction between your skin and the pillow case which decouples the system. So when you move, there is a lag between the movement of the pillow case and the pillow casing and the pillow case moves on the casing.

David

 

[MadMango]

I always thought is was due to the pear-shaped cross-section of the pillow resulting in unequal compression. When you move at night the expansion of the pillow is greater at the thick end, and this rotates the pillow case (almost like a gear train).

"Art without engineering is dreaming; Engineering without art is calculating."


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[KENAT]

I don't know zdas, my wife manages to 'roll' her cheapo foam pillow up every night, into a misshapen bolster like form. This also tends to cause the seam to be all over the place. Maybe MM is trying to do the same thing?

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[SomptingGuy]

Do you have a dog?

- Steve

 

[KENAT]

What are you saying about my wife Sompting?

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[SomptingGuy]

Dogs like pillows. And stuffed toys. They "move" them in the night sometimes.

- Steve

 

[KENAT]

Hmm, still sounds like fighting words, unless of course you're talking the the OP...

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[Skogsgurra]

Mint - that looks like a mishap piece of bread loaf. Do you sleep on that?



Gunnar Englund

http://www.gke.org

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[vpl]

I have to admit I have never worried about carefully lining up the seam in the pillow case with one of the long edges of the pillow or whether the seam is still straight in the morning.

However, might the fabric of the pillowcase also be contributing to the "problem" -- some fabrics are "slipperier" than others (to use a really scientific word), especially the new microfabrics. Those fabrics tend to move more than pure cottons, which tend to move more than cheap polyesters.

If it really bothers you, then some velcro placed along the seam in a couple places will probably take care of the problem.

Kenat, I used to do the "roll the pillow into a weird bolster shape" thing -- because the pillow wasn't supporting my neck. A new more expensive pillow might be a much appreciated "anytime" present. Having a good pillow helps ensure a good night's rest which tends to make wives (and husbands) less cranky (not implying that anyone's wife (other than my husband's) has ever been cranky, more of a personal observation that was resolved by buying new pillows with subsequent modification thanks to having a really fancy sewing machine. Ok, maybe I'm just "less cranky" rather than completely happy, but there's just so much a pillow can do.)

Patricia Lougheed

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[SomptingGuy]

I find travelling on business to Germany is often spoiled by hotel bedding. Odd pillows, short duvets. Mix that with a bit of a late dinner and the anxiety of a morning meeting.

- Steve

 

[TGS4]

Mint - I have had that issue too. The pillowcase "twists". It's always the same direction, too - counterclockwise as viewed from the open end. Some of the above explanations seem plausible.

On the good side, my wife uses the "twist" to distinguish her's from mine after laundry is done.

 

[MintJulep]

I will have to do a better job of observing if the direction of motion is consistent with respect to pillow or open end of the case.

The dog has recently taken to sleeping in the lap of the memory foam teddy bear, so I don't think I can blame the dog. The bear on the other hand may be the culprit.

 

[Skogsgurra]

It is a fascinating problem and well worth some scientific study. David's rheological explanation was greek to me - so I think it must be correct. Can you please rephrase that in engineerish, David?

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[BigInch]

Its the gremlins living under the bed. They want their old pillows back.

We are more connected to everyone in the world than we've ever been before, except to the person sitting next to us. Lisa Gansky

 

[btrueblood]

Your memory foam pillow likely has a twisted memory. A few minutes of electroshock therapy might clear it up...

 

[zdas04]

Gunnar,
Basically I was saying that in a traditional pillow the filling can assume some of the characteristics of a fluid flowing in a closed container. You can see this by putting your hand gently on a pillow (without a pillow case) and sliding your hand--the the casing and the filler move with your hand and you don't see much lifting of the end of the pillow until you've traveled some distance. Now push hard on the pillow and do the same thing--the force to move laterally are similar to the low pressure test and the end still doesn't lift at once.

Now do the same thing with one of the solid-fill pillows. With gentle pressure the casing will slide over the fill until captured by the end of the casing running out of room. With heavy pressure the end of the pillow will lift.

Your head on the pillow case represents heavy pressure so the casing will not move much relative to the fill and the only surface that is free to move is the pillow case against the pillow casing.

It gets more complex because the surface between the pillow casing and the bed is constrained between two dense solids. Consequently, the pillow case ends up with a significant tension vector in the direction you move. When you bump the pillow with your shoulder it can move off the bed enough to relieve the tension by circling the foam core pillow.

David

 

[Skogsgurra]

Great! David. I think that I can understand it now.

It wasn't even engineerish - it was human language. You ought to lecture on these things

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[Artisi]

As an experiment, why not start the night with the seam in the position it achieved the previously evening to see where it ends up - maybe nicely lined up with the long edge of the pillow.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[btrueblood]

Perhaps it actually makes more than one revolution per night? Maybe we can hook it up to a Fluke Scopemeter and measure it...oh wait, that won't work.

 

[KENAT]

VPL, Mrs Kenat picked her own pillow, and I'm sure if she wanted to try a different one she wouldn't be waiting for me to buy it for her!

However, suggestion appreciated. My fear is if I buy any additional pillows/cushions they will be added to the 416 already on the darn bed. (It may be a slight exaggeration, but it seems like that many when I'm tired and just want to go to sleep but have a mound of the damn things in the way).

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