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Hot Weather and Case Colors

September 5, 2011 at 5:32 PM

 

How much of a difference does the outside color of your case make in terms of inside temperature when exposed to direct sunlight? Now that a summer of record heat is (mostly) behind us, let’s take a look at the numbers!
 
In summer it’s generally hot, and the interior of a violin case exposed to direct sunlight can easily reach temperatures exceeding 35°F more than the air surrounding it. That means when it’s an already uncomfortable 90°F outside the case, the temperature inside can reach a blistering 125°F.
 
Violins don’t like excessively hot weather either. The varnish can soften, the wood is stressed by varying levels of relative humidity, old repairs can open up, neck angles can change. I’ve seen varnish actually boil. And the brusqueness of the temperature and humidity excursions compounds the problems. So most people try to shield their instrument from too much heat.
 
A lot of research has been done regarding how to keep cases from heating up in sunlight, and some people have even tried to do something about it. But that’s not the purpose of my blog today – I want to talk about the color of the case. Will a black case heat up more than a light-colored one?
 
It’s common knowledge that a black car parked in the sun will become hotter inside than a white car, and that partially explains the popularity of white limousines in L.A.. It’s because dark colors absorb more sunlight compared to light colors, which reflect more of the sun’s radiation, thus transforming less of it into heat which permeates the structure. The same goes for cases.
 
And yet, the majority of my clients (56% to be precise) prefer cases sporting a black cover, meaning more than one out every two cases I make is black. The remaining four color choices I offer cumulatively make up the remaining 44% of my production. My lightest exterior color, a shade of beige called sable, is requested by the least amount of clients, less than 9%. So, being that black is trendy, it would appear that over 90% of my clients prefer a case that looks cool over one that actually is cool (in °F). Right?  
 
Let’s not jump to conclusions. Before the hand-wringing begins about char-broiled Strads becoming the latest fashion victims, let’s see how much of a difference it really makes if your case is black or beige. 
 
Those of you who have been in Cremona in the summertime know how hot it can be. During our August vacation last month the maximum temperature registered at my workbench was 87°F, when I was thankfully at the beach. So Cremona is unquestionably a good place to test violin cases for sunlight absorbing and reflecting characteristics.
 
On July 25, 2005, I set two violin cases with screw attached cover into direct sunlight out in my courtyard starting at 2:30 PM, aligning each one the same way and making certain there would be no disturbing factors like creeping shadows to spoil my test. The cases were two identical models made in my workshop, the only difference being that one had a sable beige cover and the other one had a black cover. Each was equipped with a wireless temperature and humidity probe while a third probe collected ambient data, and the temperature and humidity numbers from all three were recorded every five minutes for an hour and a half. The results?
 
Starting at an ambient air temperature of 92.7°F, within 30 minutes the temperature inside both cases had surpassed 100°F, and predictably the black case after 90 minutes was the hottest inside, at 123.8°F. Surprisingly, however, the interior of the sable beige case was only 4.5°F cooler at the end of the test (at a respectable 119.3°F), and the temperature advantage over the black case was only 2.7°F after the first half hour and 4.3°F after the first hour. Conclusion: unless you really leave your case sitting out in the sun in your courtyard for an hour and a half during scorchers on a regular basis, the difference in temperature that the lighter color cover offers is not really that much at all.
       
To get the entire picture I also plotted the relative humidity effects as well. Starting from 53% and 54% for the black and the beige case respectively, after 30 minutes the relative humidity had zoomed up to 80% and 78% (thanks to the “pressure cooker effect” that plagues mostly air-tight cases), to then slowly descend to 70% and 71% after the first hour and to 64% and 66% at the end of the test. The ambient relative humidity ranged between 39% and 43% during that time. Conclusion: the slight temperature advantage offered by the beige cover afforded little effect on relative humidity excursion, usually around 2% difference.
 
As a disclaimer, I must point out that these test results regard typical examples of my own cases, i.e. multi-layer laminate shell cases with screw-attached covers including full-sized music pouches. Cases without music pouches (and those without a cover at all) will behave differently. So will cases with the shell made of fiberglass or high-tech materials. Even interior design differences will make a difference. Yes, more interesting information came out of this test as well, but I’ll stop here because I’ve made my point.
 
All you fashionistas can now take a sigh of relief. In my opinion, you can go on enjoying your trendy black cases (with screw-attached cover, music pocket, etc. etc., see above) without feeling guilty at all.
 
Cheers!


From Tom Bop
Posted on September 6, 2011 at 2:20 PM
I also live in a hot climate, and researched the effect of lighter roof shingles a few years ago. I was also surprised that the color didn't make that much difference- the lightest ones were only about 7% cooler in the house than the darkest ones. In cars, most of the interior heat comes from the solar radiation coming into the windows, and reflecting back at a wavelength that can't "get out" of the windows. I've heard the color of the car makes little difference. Maybe those limos have such heavily tinted windows, tho, that the white helps some.
From Marsha Weaver
Posted on September 6, 2011 at 3:18 PM

Thanks for your excellent data!

This has been a scorcher of a summer by northern Indiana standards!  My home isn't air-conditioned, so temperatures inside the house reached nearly 100 degrees on several days (with the humidity taking the heat index to well over 100).  I was freaking out about my violins the whole time, but so far I'm not detecting any problems.

Both my violin cases are black (no color choice available), which has been a real source of worry for me.  I'm glad to hear that case colors apparently don't make all that much difference in heat resistance.  I think I've at least partially gotten around the violin-case-as-sauna problem when I've had to take my violins out into the sun by covering them with nice, thick, white terry-cloth towels.  The towels feel relatively cool to the touch even when sun is an issue, and the surface temperature of the case underneath feels surprisingly low.  I keep the air temperature in the car cool, but not frosty.  So far, so good.  Keeping my fingers crossed. 


From Dimitri Musafia
Posted on September 6, 2011 at 3:43 PM

To Tom: you're absolutely right about the tinted windows. In fact, the windowless trunk of a sedan is much cooler than the passenger section in a car parked in the sun for a while: try it and see for yourself.

I've also seen that in modern design cars the windshield is very raked, and while stylish and aerodynamic, this allows more sun to beat onto the dashboard, increasing the heating effect. In my wife's car (a new mininvan), the dashboard turns into a hot plate that heats up the whole place; in my own car (a 14-yr-old sedan with a much more upright windshield) the effect is much less.

To Marsha: you've found a good solution!


From Joseph Galamba
Posted on September 12, 2011 at 4:38 AM

This is something a physics student wouldn't be surprised by (if I remember correctly we do a lab with black and white coffee cups here at Oberlin).  

I believe about half the energy of the sun that gets to the ground is infrared and probably almost everything being given off by the hot stuff around the case is infrared.  Of course, visible light is also heating the violin case, but if one fabric is reflecting visible light and absorbing IR and the other is doing the opposite you won't observe any difference at all or maybe the opposite of what you would expect based on the color.  

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