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La Folia   
4 hours ago, Dimitri Musafia said:

...if I'm not mistaken the adsorbing phenomenon would have had to release 37g of water vapor per kg of air.

Is this possible?

 

How many kg of air is in one of your cases?  ;)

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9 hours ago, La Folia said:

How many kg of air is in one of your cases?  ;)

That's a tough one, considering how complex the surfaces are. 

Reason for which while not sleeping last night, I thought of preparing a special case for a solar radiation test. Usual shell, usual cover, but NO interior at all. Just empty space. I'd waterproof the interior surfaces to minimize both moisture adsorbtion and absorbtion and have the added benefit of being able to actually calculate the air volume and thus the kg. of air inside. A barometric sensor would be included.

Then I'd put it to the overheating tests like I've done in the past (along with a completed case for comparison) and chart the outcome. The results should help define some of the aspects of the issues we have been discussing.

Any comments or suggestions? 

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RE possible passage of moisture through wood laminate case shells during solar exposure

Someone had asked if it were possible for moisture to pass through wood laminate, which as is noted is a number of wooden plies with glue uniformly distributed in between. So I just performed an experiment in which 40ml of water were poured onto the inside of the lid of a wood laminate case shell and left there to see what would happen. Note that the inside of the wood was unfinished (i.e. no lining, no glue to block the passage of moisture).

Ambient temp 24°C, RH 60- 65%. Test starting time 9.50 AM. The water stagnated for a while, partially absorbed by the first layer of laminate while it spread via the capillary effect, and a little of it did eventually seep through the joinery between the lid panel and the sidewall (again less glue was present there than normal).

Even though there was standing water for over an hour, none of it passed through the laminate itself, and by 14.50 (5 hours later) the shell was dry to the touch.

Although this test was not performed at high temperatures, I think it would be safe to rule out measureable quantities of any kind of absorbed or adsorbed moisture passing through the structure of the case shell itself during solar exposure tests owing to porosity of the material, to the point of causing the observed abrupt changes in RH within the case.  

Any comments?

untitled2a.jpg

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GeorgeH   
1 hour ago, Dimitri Musafia said:

Any comments?

Just that water vapor (gas) can pass through materials that water (liquid) cannot. For example, that is how Goretex works.

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2 hours ago, Dimitri Musafia said:

Hah! Didn't think of that... hmmmm.... how about a test with steam?

In an elementary school science project I helped my son with long ago we built two large box like chambers out of clear plastic to do RH experiments (details not important).  In one chamber the RH was ~45% (ambient).  In the other we raised the RH in increments up to 90% by heating water on a hot plate.  Just an idea. 

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7 hours ago, GeorgeH said:

Just that water vapor (gas) can pass through materials that water (liquid) cannot. For example, that is how Goretex works.

 

7 hours ago, Dimitri Musafia said:

Hah! Didn't think of that... hmmmm.... how about a test with steam?

Hi Dimitri, 

you could make a Gore-Tex coated shell,  the impact of an advertisement for extreme violinists on top of Everest would not have rivals.....B)

I will come to collect the bill for the rights of this idea:P:D

Maybe call Reinhold Messner.........

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HoGo   

What about simple experiment...

Take (clear) plastic box with good seal that contains approximetely as much air as violin case and measure the RH over temp range again like you did with case. Properties of simple plastic box are easy to know (simple PP doesn'r adsorp water etc...) so you'll find out whether the phenomenon is result of case materials or just of the  enclosed air-humidity. You can also add pieces of various materials (plush or plywood or foam or VSO) to find out what is causing the increse in humidity.

 

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1 hour ago, HoGo said:

What about simple experiment...

Take (clear) plastic box with good seal that contains approximetely as much air as violin case ... 

Thank you for the suggestion, but I prefer to re-create real-world scenarios as much as possible, in other words working with actual violin cases. 

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15 hours ago, Davide Sora said:

 

Hi Dimitri, 

you could make a Gore-Tex coated shell,  the impact of an advertisement for extreme violinists on top of Everest would not have rivals.....B)

I will come to collect the bill for the rights of this idea:P:D

Maybe call Reinhold Messner.........

If that's what it takes, I'm all for it :-) !

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