Yellowing of Finish:

The long term clarity of finish when exposed to sunlight is an important issue to custom rodbuilders. Many subjective claims are made which compare one finish to another with descriptive phrases. If there was a quality control group that worked with various products for custom rods the following would surely be done.

There is a laboratory instrument called a colorimeter that is used to measure the percent transmittance of materials that allow light to pass through. The measure of the amount of light that will pass through the material is compared to the amount of light that will pass through demineralized water. The test device can be found in any power plant or can be purchased for under $ 200.00

The test would require a two ounce bottle to be filled with the finish, heat to remove air bubbles and allowed to cure. A separate test specimen could be prepared at the same time for each finish included in the test. All bottles could be collectively stored together and exposed to the same amount of sunlight. A periodic reading of percent transmittance of each bottle would document the results.

It would be interesting to perform this study over the long haul to see what the final results would be. It would not be influenced by blank color, thread color or color preserver.

I have a colorimeter and would perform periodic readings. If I were to send all finish manufacturers a test bottle and ask them to fill it on a certain date they could be returned for photographing and dated transmittance measurements. Or better still maybe one of the manufacturers will to the testing themselves and use it as a proof source statement for advertisement instead of the term "will not yellow or turn brown".

What say you?

Gon Fishn

Does 'exposure' need to be the same for the test results to be comparable? eg, do you then also need to measure and control lumens at the sample under test, or something like that? lol



Edited 1 time(s). Last edit at 04/13/2006 06:27PM by Steven Libby.

Interesting project!!!...I used to work for PPG Industries in their paint and stain division. An independant company called Paint Quality Institute would do long term tests to check durability, fade, etc. of different manufacturers products including deck stains and clear coats. They have acres of material out in the sun and it's been there for years...they keep testing and adding products to their collection of tests every month. The industry has come to rely on their tests very heavily. Perhaps there is a need for this type of testing for the rod building community testing epoxies and finishes. It seems that there would be an awful lot of interest in the results.

One question..Would you get better results by applying the products in a thin coat over clear glass micro slides than letting it set in a solid bulk?..I only ask because the manner in which the product is used is in layers of applications and not "molds" of the product. If a test was to be done on this level it should be tested in a manner inwhich it is normally applied...which would be in a few layers on a solid transparent surface wouldn't it?..I know Andy at Lamar has done a lot of product research in coming up with a formula he felt comfortable marketing that involved putting the product on a white background and letting it weather in the sun and came up with alot of varied results from formula to formula. Maybe doing it on a clear transparent surface would make it possible to detect any tinting caused by UV by a device rather than the human eye. I'd love to hear what you come up with!!!

JS Harding

The percent transmittance of light through a constant dimensioned test sample bottle will tell you how much light will pass through a given thickness. These test samples would be placed in identical clear glass colorimeter bottles. All bottles have the same refractive index. Each sample would be the same dimension. The brightness (lumens) of the light source is a constant for all samples when run on a calibrated colorimeter. This would be the way a test laboratory would compare one product with another. If the clarity of the resin is the item in question simply report the results in a manner that is measurable. Mix them up store them in the same place, expose them in the same manner, keep the time of exposure consistant for all and read the numbers. I would also like to see the percent transmittance of the two finish components as a function of time in the unmixed state. The hardner component could cause quite a stir in come cases due to complex amines and ferric ion contamination.

Bill,
I think that Steven and Jeff make some very good points about testing the finish the way it will be applied. I wonder if there is a way to accelerate the testing so that you do not have to wait for years for the results. Couldn't the finish on a sample blank be exposed to a high intensity light source to accelerate the testing??

Emory: The actual coloring will be a function of the thickness of the film of finish on a particular rod. The thinner the film the less of a color shift will be involved. The test I am proposing will only compare the light transmittance of finish 1 vs finish 2 when using a constant test parameter. Certainly the test bottle will filter out more light than a thin film on a rod but the overall effect of the test will tell us which finish is clearer and what are the long term uV exposure effects when all are subjected to the same conditions. I do not have a cheap source for increasing uV rays unless we load some of the test bottles on the next space ship trip to the outer space. Maybe Ralph can talk to some of his buddies at Boeing and arrange for some high altitube testing!.

Bill,
Yes, I understand and that makes sense if you only want to know which will discolor the least independent of how it is applied and that is probably what is most important.
But I would bet that artificial lights are available that would significantly accelerate the testing.

Emory,
FYI, we have had ThreadMaster in what is called an accelerated weather chamber on a number of occasions, and it has passed all long term clarity and durability tests with flying colors. Sometime this summer my chemist and I are going to put all other brands of finish in the chamber for testing as well. I'll post the results here when we get them back.

Bill, you may need to re-evaluate your statement regarding the exposure to sunlight. Discoloration happens to finishes prior to mixing and in the complete absence of light altogether. Take a bottle of (insert brand of finish here) and stick it in a totally dark closet....most all of them still turn yellow ...sometimes iced tea brown in an unmixed state. There are components in the hardener that are just as susceptable to breakdown through heat (if not moreso) than UV light. If any finish manf. is still having discoloration due to iron contamination, I think they better re-evaluate who their raw material supplier is.

Feel free to send me your insturment anytime. Better yet, I'll send you a kit of ThreadMaster and you can perform the test yourself, so that there is no chance of accusation of bias.

Jeff, thank you for mentioning the Paint Quality Institute...a bit of trivia.... the chemist who designed ThreadMaster was one of the longtime "higher-ups" on the Board of Directors at the aforementioned institute.


Andy Dear
Lamar Fishing Products

You can read about Accelerated Weather Chambers here:

[www.etctr.com]



Andy Dear
Lamar Fishing Products

Bill, nothing wrong with that test, but I feel if people are REALLY that concerned they will take teh time to perform this test themselves. You mention the amount of finish affecting the results, so will the "Strength" of sunlight. This is why certain people notice a problem, and others don't.

As far as Hardener browning in a dark closet, that's obvious. What I have heard which I am skeptical about is the mixed epoxy will also turn darker in a dark closet. Now I know for a fact that exposure to NY Winter sunlight for 4 months hardly turnes epoxy darker (even Glasss Coat), so how would that happen in a dark closet?

Since the light from the sun contains not only light from the visible spectrum, but also ultrviolet and infrared light, you will need to determine the percent transmittance (actually absorbance will be better A = - Log (%T/100) from the visible to the ultraviolet). You will then have a spectrum of each of the samples of epoxy.

from that you can then expose them to sunlight for different periods of time and note the changes in the spectrum. By doing this you will be able to determine which wavelengths of light are being absorbed. However, absorbtion of UV will likely have an effect that will cause molecular changes which will affect the color of the sample thereby interfering with the spectrum. For example, if the epoxy turns yello, it is likely that the epoxy is now absorbing in the blue or violet region. Arghh!!.

Bill I think it is possible to obtain a spectrum of the samples that have been not been exposed to sunlight to get an idea of their clarity. However, once molecular changes occur the colors of light being absorbed will be affected.

One thing that will be obtained is the change in the amount of light beong absorbed in the blue end of the spectrum.

Good grief, I just retired from this stuff.

Mike Blomme

From a practical sense, I see nothing worthwhile from Bill's idea, though it has definite merit. ThreadMaster is the clearist epoxy I've seen short-time.

Stan

The most convincing test I saw recently was in Rodmaker Vol 9 # 1 page 27 fig 1. The photo of six popular finishes in a leveling scenerio side by side on a peice of glass. I had the opportunity to see this peice of glass first hand on the way back from Charlotte, I could've cared less about the level finish on glass. What I saw was a clarity test. by looking straight down, or from the side (a thicker angle), it was obvious to me that the two clearest finishes by far were the Diamond II and the Threadmaster.

Bill, all tests are a great thing. I'm willing to make a wager on both Threadmaster and Diamond II as being #1 and #2 (or #2and #1) of this test. Maybe a large pastrami from certain NY deli if I'm wrong, for some more of that Cajun Jerky if I'm right?

There have been no long term clarity tests done on the current version of Diamond II to my knowledge, save for kirkman's glass sheet. Before Gene released the current version of Diamond II on the market, he gave me the opportunity to work with one of the preliminary samples for eval. It was a nice finish...leveled well, and was flexable, but yellowed as bad as all the others in less than 4 days. Like I say though, what Gene is selling now is not the exact formula that I ran my tests on.

Mixed epoxy will also turn brown in the absence of sunlight as well. I have a casting rod that a good friend built for me a while back ago. It has a white underwrap in the butt wrap. I have fished with it twice, the rest of the time it has been in a rod tube....pulled it out the other day, and it is turning yellow.

I am going to inquire today about running a test in the accelerated weather chamber using every resin I can get my hands on. It'll be interesting to see what happens. The other thing we need to take into consideration is the overall working properties of the finish as well. For example I know of one epoxy on the market currently, that actually stays pretty clear, but it is unbelievably difficult to work with, doesn't mix well, doesn't stay in one place on the wraps, takes many days to cure, and in addition is the most expensive. What good is non-yellowing if all the other attributes are bad?

What we probably should do is come up with a list of criteria by which resins are judged:

Ease of mixing
Ease of leveling
Cure Cycle and rotation time
Clarity (both long term and short term)
Shelf Life (unmixed) Mainly, how long will hardener stay clear at room temp.
Hardness
Flexability
Adhesion
Bubble Release (can it be heated? Does it need to be heated?)
Tolerence to mixing errors
Tolerence to Amine Blush
Price
Availability
Technical Support

Anyone have anything else we could add?


Andy Dear
Lamar Fishing Products

I'm not sure that sunlight has anything to do with the yellowing or darkening of epoxy finishes. Most will darken even if kept in a dark closet, completely away from UV light. Age and temperature are more important that UV light exposure if we're talking about yellowing or darkening.

............

Tom - I have a test stick which sat in the sun for 9 days during the summer, where all the finishes on it turned brown except Aftcote. I put a piece of foil along the backside, so you can see how much each finish darkened.

[www.rodbuilding.org]

It's been 10 months and it has been out of the sun, and it still looks the same, with the side where the foil was being pretty much clear.

I've also put test sticks out in teh sunlight during this past winter, for 3 months, with a piece of foil - and the finishes hardly changed colors. So I know the stronger the sunlight, the quicker the finish will turn colors.

Tom,
Light is about half the problem (according to my chemist) and heat is the other half, at least when it comes to breakdown of the hardener. The Resin is not as succeptable to these two factors as the hardener is...that's why the resin always stays clear in an unmixed state

My question is this: Why are we so positive that it is the UV spectrum of light that causes degradation?


Andy Dear
Lamar Fishing Products

Billy,
Aftcote stays pretty clear once it's mixed, but it turns brown unmixed in the bottle pretty quickly....at least mine did.


ANdy Dear
Lamar Fishing Products

No, it's not only yours. My bottle is 2 or 3 years old (pre-production version), and it's nice and brown.

Andy - I do not know if it's UV, if it's sunlight, if it's heat, or NY air - I do know that if people are concerned with their finish turning colros THEY NEED TO test their finish in their environment. Some people have no problem with Flex Coat yellowing, or cracking - I have no doubt this is true, but I also know for a fact on all the rods used in my area, those with FC crack & yellow.

I'm confidant in saying that MY RODS which have Aftcote & ThreadMaster on them will stay very clear over the same time frame than other rods which I have used other finishes. I know this for a fact based on my testing Aftcote, and your testing ThreadMAster as I think teh sun is stronger in Texas than in NY, lol. That will not stop me from sticking another test stick or 2 out there in a couple of weeks with Permaglos & ThreadMaster.

I just got "tentative permission" to supply an independent company with 12 Test samples to be put in an accelerated weather chamber sometime this June. I'll post pics. after this takes place.


Andy Dear
lamar Fishing Products