I am building operative temperature models of the collared lizard (Crotaphytus collaris). I have found several estimates of % reflectance of the lizard, but I have not found much information on spray paint reflectance values. Preferably, I would find a green colored primer spray paint in the 14-18% reflectance range - but other primer colors in this range would probably work equally well.
Hi Casey,
I'm surprised no one has answered this yet, as this question (and its answers) are most important for physiological ecology and evolution.
So, I see that you want to use a primer that is essentially neutral gray. Good move. I suspect that you're not going to have a hard time finding a gray paint that roughly matches this. And, presumably, you're wanting matte paint, so as (1) to be able to actually measure reflectance and (2) not deal with different emissivity values (maybe?).
I found this question fascinating, so I checked around. There are values for absorptivity of paints (such as this horrible resource: http://tinyurl.com/kqlblva). Someone correct me if this is incorrect, but maybe the following can be of some use: Total energy incident on a surface is the sum of absorptivity, reflectance, and transmissivity. Most materials thick enough not to transmit energy, so then:
absorptivity+reflectance=1
So, if you can get the absorptivity values from pain manufacturers, you'll have your reflectance %.
Again, sounds like an awesome study!
Patrick,
Yes, that looks correct. I have seen tables with general colors and material reflectance - absorptivity - emissivity values, similar to the one you posted. I may be over thinking this, but I know that colors can vary considerably depending on the contrast, hue, etc.of the particular paint (i.e. not all white primers would be the same). In the past, researches building OTM's have used spectrophotometer equipment to test a handful of candidate spray paints. This has made me think I should use a paint that I know the specific value for - but manufacturers don't seem to have this data on spray paints (a few do post it for house paint- which may be an alternative, but I was concerned with application and inconsistent thickness). I have found some specific paint in the literature that is close to what I need, but I thought I'd ask around to match reflectance more closely.
Thanks for your input,
Casey
Patrick,
So I had only glanced at the website you posted, thinking I had already read through it. After second look, I realize it does have some specific pants. It appears that this may get me closer to what I am looking for. Thanks!
Casey
You're right that direct measurements of reflectance will be best, especially since they will be internally valid (i.e. you're measurements of real lizards can be compared directly. The other advantage is that total reflectance could be identical, but the paint could be highly reflective in one band but not in another (i.e. very different to how the lizard's actual skin in reflecting energy). Maybe it would be good to write to the company...or do you have access to a spectroradiometer or similar equipment? If you do have access to an OceanOptics unit or something like that, you could always go to the your local hardware or paint store and ask for samples. Buy one can of primer and spray a bunch of small patch of cardboard or something. Then, tell them what you're doing exactly. They'll think you're nuts. See if they have extra, half-used cans in the back and would allow you to spray a small amount on the patch. Label these and go measure with the spec.
Ok, so maybe I'm not over-thinking this. Yes, I have been trying to get access to equipment. I hope to know if we have appropriate equipment on campus this next week (I've emailed a few faculty that I was told may have access to this type of equipment). I plan on reporting all paints and corresponding reflectance value that I get- maybe some one else will end up in my shoes and not have access to the equipment. Crossing my fingers.
You could also publish that kind of info online. I think it's general enough.
And I definitely don't think you're over-thinking this. Another option is to exploit variation in reflectance profiles (where peaks are above and below the value for a given wavelength band on a real animal). In this way, you're essentially engineering phenotypes of your copper/metal models. With enough replicates, I can see this making a really cool paper. Plus, you won't need to mimic the absolute reflectance profile. You'll just have to bound it. Who know, you may see that what is optimal for certain parts of the body are NOT the color that the lizards actually are...then you could explore constraints, trade-offs with mating coloration, etc. It might save you some time trying to set up the experiment and make you end up with cool model (no pun intended...a cool model in the field and a cool model in your stats program). Depends on how many metal models you plan on making...
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