UV absorbance testing on waxes and sealants

[jbgrant]

I'm looking for any independent experiments, articles, or data that actually looks at the ability of waxes or sealants to protect paint from UV as so many products claim. Anybody come across anything with some objectivity? I really would like to put these claims to the test because UV protection is so readily touted. Consumer reports??

I am considering the following experiment:
1) acquiring an accurate UV index photometer
2) building a test box with a UV probe and strong CFL UV source (black light)
3) treating sections of uncoated framing glass and/or plexiglass with different sealants/waxes/lsps
4) measuring the ability of the products to absorb (or reflect) UV light (when compared to control blanks)

I would taking measurements a) after the products has cured, b) after 8 hours of exposure to a realistic UV intensity, c) after simulated rain or washing, d) after 1 week exposed outside in Indiana, and e) after 1 month of exposure.

I may even build an apparatus to expose four or more products to UV light simultaneously so the experiment would not take forever to execute.

I would need extremely small quantities of several products (free samples!).

Questions:
1) Would it be safe to assume that most sealants or waxes would function when applied to glass or plexi?
2) Are there other alternative substrates you can think of that would allow light penetration and are affordable? I was thinking I could have a body shop clear-coat some plexi, or I could do it myself.??
3) Is there a more appropriate way to measure UV absorbance/reflectance?

It sounds like this could generate some fairly useful data if I can get a meter that actually measures only UV.


From wikipedia:

The UV index is a number linearly related to the intensity of UV radiation reaching the surface of the earth at a given point. It cannot be simply related to the irradiance (measured in W/m2) because the UV of concern occupies a spectrum of wavelength from 295 to 325 nm and shorter wavelengths have already been absorbed a great deal when they arrive at the Earth's surface. Skin damage, however, is related to wavelength, the shorter wavelengths being much more significant. The UV power spectrum (strictly expressed in watts per square metre per nanometre of wavelength) is therefore weighted according to a weighting curve known as the McKinlay-Diffey Erythema action spectrum, and the result integrated over the whole spectrum. This typically gives a figure of around 250 in mid-day sun and so is arbitrarily divided by 25 to generate a convenient index value, which becomes essentially a scale of 0 to 10 (though ozone depletion is now resulting in values above ten as commented above).[3] Because the scale is linear and not logarithmic, as is often the case when measuring things such as sound level or brightness, it is reasonable to assume that one hour of exposure at index ten is approximately equivalent to two hours at index 5, although other factors like the body's ability to repair damage over a given time period could detract from the validity of this assumption.
To illustrate the weighting principle, the incident power density in mid-day sun is typically 0.6 mW/(nm m2) at 295 nm, 74 mW/(nm m2) at 305 nm and 478 mW/(nm m2) at 325 nm. (Note the huge absorption that has already taken place in the atmosphere at short wavelengths.) The weighting factors applied to these figures are 1.0, 0.22, and 0.03 respectively. (Also note the huge increase in damage caused by the shorter wavelength, i.e., 305 nm is 22% as damaging as 295 nm, and 325 nm is 3% as damaging as 295 nm.) Integration of these values using all the intermediate weighting values over the spectral range of 305 nm to 325 nm produces a figure of 264, which is then divided by 25 to give an index of 10.6.[3]

[JonMiles]

You could always make up dilute solutions of various products with a suitable solvent that does not cause interference in the uv region of the spectrum and use a UV-vis spectrometer for the absorbance of a given product in the UV region. This would give you a decent idea of the absorbance of each product based on peak integration to give you a comparative analysis of each. I'd bet there would be some surprises on the absorbances in other regions of the visible light spectrum with some products that may contribute to paint darkening and and even color enhancement.

As for reflectance of the products, that would be difficult to determine. I am not really familiar with reflection from an instrumentation standpoint, but absorbance would be pretty simple overall.

[john b]

did you guys eat paint when you were kids?

[jslym777]

apply each product to a thin piece of glass/plastic and record the UV rating underneath each with a UV meter, maybe you could go to an optical store/doctors office to have this done if they let you haha. the glass/plastic is your constant just record the UV rating under each piece before applying the products to make sure you get the same reading. it seems like a similar test to sunglasses.

[Setec Astronomy]

Ha, I forgot I did this until this thread reminded me, last year when there was a lot of talk about (or at least I noticed a lot of labeling on products I had/was considering) UV protection/absorbtion, I borrowed a black light and looked at all my products under it hoping to learn something. I didn't.

[Mike Phillips]

I don't know of any objective or meaningful tests...

Been on discussion forums since discussion forums have been around and from time to time a thread like this pops up... "testing" topic, best of luck to you with the follow-through. As to the comment about testing products on glass, I dealt with a forum member years ago that was going to do some type of similar test using glass slides, as in the kind used with microscopes. I shared this with a chemist friend and he glass is very different than car paint and then said car waxes, paint sealants etc. are not normally formulated to bond to glass so any tests related to car paint but the testing is done on glass would kind of skew the usefulness of the results.

Just to interject... the primary goal to make your car's paint job in totality last over the service life of the car is to maintain the car's top coat or clear layer of paint. Paint manufactures include UV inhibitors or UV screens in this layer of paint to protect the color coat under it and theoretically if you do a good job of periodically washing, claying when needed and then sealing the paint with some type of wax, paint sealant or coating then the paint job will hold up over time. The idea being instead of adding UV protection on top of the clear layer of paint, take care of the clear layer of paint.

[jbgrant]

Paint manufactures include UV inhibitors or UV screens in this layer of paint to protect the color coat under it and theoretically if you do a good job of periodically washing, claying when needed and then sealing the paint with some type of wax, paint sealant or coating then the paint job will hold up over time. The idea being instead of adding UV protection on top of the clear layer of paint, take care of the clear layer of paint.

I completely agree. My point is just that those UV inhibitors/screen blended into the paint have a half-life and after say 10-20 years or even more there's just no way the clear can do its job and protect the base if the car has not been garage-kept most of its life. Would it be safe to say that most clearcoat failure resulting in separation from the basecoat (not wear-through) is due to oxidation promoted by UV damage?

[embolism]

Some of the research I did indicated that the UV inhibitors added to factory clearcoats migrate upwards towards the surface of the clear as it cures and is baked into the finish.

That implies that as people polish and remove clear in order to level their paint, they are removing the majority of the UV protectants that are present in the topmost layers of the clear.

Keep in mind however, that we are talking about microns of thickness here so if someone polishes their ride once every year for 10 years using good technique, and they had a thin clearcoat to boot (older model cars have more clear than today's cars), then maybe they have gotten rid of their UV protection. Even though the car still has clear, the paint underneath is now exposed to UV which might take another few years to affect the paint underneath.

Bottom line is it's somewhat of a non-issue when you take into account the service life of a majority of the cars out there today.

[FUNX650]

Keep in mind however, that we are talking about microns of thickness here so if someone polishes their ride once every year for 10 years using good technique, and they had a thin clearcoat to boot (older model cars have more clear than today's cars), then maybe they have gotten rid of their UV protection. Even though the car still has clear, the paint underneath is now exposed to UV which might take another few years to affect the paint underneath.

Bottom line is it's somewhat of a non-issue when you take into account the service life of a majority of the cars out there today.

When you speak of "service life' are you referring to the length of time 'a majority of the cars' are expected to function as a means to get from point A to point B successfully before they no longer function as that so intended means, or mode of transportation? Or, are you implying that folks trade or sell their vehicles before clear-coat damage, whether by removing an excess amount of clear-coat by overuse or misuse of abrading products, is evident? Just curious.

I was under the impression that today's vehicles were 'lasting' longer; and, given today's short-term (and possibly long-term) dimly forecasted economy, many people are having to keep their vehicles longer than they probably expected. Perhaps these impressions are wrong. If not, then:

I do feel that the care of vehicles, whether it's mechanical, electrical, or paint is an issue.

[embolism]

Service life to me means just that. The life of the car regardless of owner. If an owner compounds his car heavily every season, then it's pretty obvious that the paint will not last for the service life of the car.

I drove my last car for 14 years (bought it at 3 years old) and intend to do the same with the 2007 model I picked up last year. I could have driven my old car for another 5 years but the body was starting to rust out (last 5 years it was kept in a condo's underground heated garage so the rusting just took off).

I was speaking only in terms of paint. I, like many noobs, was doing everything by hand mainly b/c I was afraid to use a machine on my car. My research has convinced me that I shouldn't be afraid so I bought a polisher this year.

Are cars lasting longer? Up to a point I'd say yes, but you are continually getting manufacturers trying to squeeze the poor parts guys to the last penny so what do you expect... you get cheaper parts in both price and quality...

In terms of paint, it is well documented that paint thicknesses are much thinner than the cars of even 5 years ago. Everyone is looking for ways to give you less for the same price or more. Heck, you can't even buy a piece of Bazooka nowadays that is a solid block of gum. Instead, it's got these tracks cut out of it so they can squeeze a few more pieces out of the batch they made up.

ok back to paint. I've read a few posts on here where someone had never waxed their new car (b/c it was a new car and they assumed it was protected from the factory) and it was starting to show oxidative damage in spots after only a few years. Maybe it was a bad batch of clear or maybe putting on that sacrificial barrier of wax or sealant is actually doing something to protect the finish from UV damage.

I guess my point is that if UV protection was such a big marketing goldmine, someone would have latched onto it by now (they probably haven't b/c it is a slow process and they want to show immediate results like protection against a flame thrower). All of these LSP products have similar ingredients so I think it's more important that you have that layer of protection, rather than having on something specific.

It is an interesting theory though. Maybe if we knew definitively that brand A was better at protecting from sun damage, we would use it in the summer just like we use certain brands in the winter due to their known durability.