Yellowing - How To Prevent?

[BlueMax]

10 hours ago, ErikElvis said:

I would like to know how my shuttle tydirium and b wing yellowed sitting in a dark room. And they’re gray plastic. 

That’s the thing... it sure ain’t exposure to UV in your case, though prior exposure might play a part. Yellowing can occur regardless of the color of plastic, just a matter of whether it is obvious or not.

 

Maybe a few questions you can ask answer:

Were the items handled with bare hands regularly prior to storage?

Is it an even yellowing? Does the yellowing somewhat correspond to where contact was made when handling?m, or mainly the “top-sides” and parts generally visible to the eye?

How long were displayed in regular settings before being settled in a dark room? Why kind of lights were you using in regular settings?

How hot and humid is your dark room?

 

[MKT]

On ‎9‎/‎5‎/‎2020 at 2:21 AM, slide said:

The biggest factor is likely the Plastic's own chemical composition and quality of the mixture/moulding processes.

I believe this as well.. I have a new item that aggressively yellowed in only 8 months from just being in a dark room sealed display, and the only light exposure was to LED lights. After 16 months, the yellowing is worse than 30+ year old toys..

The yellowing was on selective whole parts of the figure, so it is definitely down to the plastic composition used for these parts.

 

 

[BlueMax]

The next logical question is: if the plastics used is the base problem, is there still anything we can do to prevent yellowing, or at least delay it? Or is it futile no matter what?

[Sanity is Optional]

3 minutes ago, BlueMax said:

The next logical question is: if the plastics used is the base problem, is there still anything we can do to prevent yellowing, or at least delay it? Or is it futile no matter what?

Well, temperature is an accelerant for just about every chemical reaction. So keeping them cool will help. Also removing other possibly contributing factors (like oxygen, UV light, humidity, skin oils) will at least keep the process from accelerating.

Even if yellowing is inevitable, you can still ameliorate the degree of yellowing.

[ErikElvis]

5 hours ago, BlueMax said:

That’s the thing... it sure ain’t exposure to UV in your case, though prior exposure might play a part. Yellowing can occur regardless of the color of plastic, just a matter of whether it is obvious or not.

 

Maybe a few questions you can ask answer:

Were the items handled with bare hands regularly prior to storage?

Is it an even yellowing? Does the yellowing somewhat correspond to where contact was made when handling?m, or mainly the “top-sides” and parts generally visible to the eye?

How long were displayed in regular settings before being settled in a dark room? Why kind of lights were you using in regular settings?

How hot and humid is your dark room?

 

They were hardly handled. And on a shelf in a closet. The rooms vents are closed but it doesn’t get that hot, cold, or humid.   The discoloration is uniform.  The only thing I can think of now is I had a large iguana cage in the room for a couple years. So it was prob pretty warm in there during that time but I can’t imagine over 85. I’ll eventually try to clean them or maybe sit them out in the sun to bake for a couple days to see if that lightens them. 

[sqidd]

2 hours ago, Sanity is Optional said:

Well, temperature is an accelerant for just about every chemical reaction. So keeping them cool will help. Also removing other possibly contributing factors (like oxygen, UV light, humidity, skin oils) will at least keep the process from accelerating.

Even if yellowing is inevitable, you can still ameliorate the degree of yellowing.

Cabinets that pull a vacuum are going to be a fortune!

I'll be able to re-create the ending to three Alien movies though. That's fun!

 

1 hour ago, ErikElvis said:

They were hardly handled. And on a shelf in a closet. The rooms vents are closed but it doesn’t get that hot, cold, or humid.   The discoloration is uniform.  The only thing I can think of now is I had a large iguana cage in the room for a couple years. So it was prob pretty warm in there during that time but I can’t imagine over 85. I’ll eventually try to clean them or maybe sit them out in the sun to bake for a couple days to see if that lightens them. 

Doesn't lizard urine give off ammonia or something?

[DewPoint]

I don't know about lizards, but goldfish totally do!

[nightmareB4macross]

7 hours ago, sqidd said:

Cabinets that pull a vacuum are going to be a fortune!

I'll be able to re-create the ending to three Alien movies though. That's fun!

 

Doesn't lizard urine give off ammonia or something?

They don’t but their urine does. Plus having the heat lamp on accelerates the evaporation which Would give off a smell.

Not sure if this is the cause though. Are your figures displayed opened on shelves or still in their boxes?

[sqidd]

I thought you guys would find this interesting. When I was shopping for UV tint I came across it. It;'s s test that was done for a museum(s). Interesting results and certainly a few points to think about that I wasn't aware of. Most UV films being junk the important one. I even went as far as to buy a light meter. I lucked out on that thing. It tests in the spectrum needed and was relatively inexpensive. I must have gotten the last one on the planet though. I have not been able to find more. If you want to get a light meter you're going to need to research and see if the ones you're looking at test in the right range. Which is not easy. Most of them for sale don't seem to have specs available.

https://cool.culturalheritage.org/waac/wn/wn30/wn30-2/wn30-204.pdf

[sqidd]

Alrighty smart guys (I’m not saying that sarcastically) I’ve gathered some UV data and need help processing it.

I’m using a Sanctuary UV Light meter. Here are the specs:

-The display is in µW/cm2 (microwatts per square centimeter)

-UV AB Measurement Range:0 to 2999 µW/cm2; It only measures UV AB light power output, but not the wavelength.

-Spectral Detection Range: 240 to 370 nm; Peak point: 352 nm. It does not measure UVC.

-Measurement accuracy: ±4% ±1 digits; Resolution:1.0 µW/cm2

I just collected a bunch of readings from different light sources and I need help making sense of them. All bulb measurements were taken with the light meter 3in from the bulb face.

- Slightly overcast day is 500 µW/cm2

- A sheet of glass (Detolf shelf) knocks that down to 380 µW/cm2

- LLumar UV window film knocks it down to 25 µW/cm2

 - 240 lumen LED bulb (toy cabinet bulb) is 12 µW/cm2

- 500 lumen LED bulb (desk lamp) is 8 µW/cm2

- 800 lumen LED bulb (overhead room light) is 20 µW/cm2

- 825 lumen compact florescent bulb is 17 µW/cm2

- 60w incandescent bulb is 38 µW/cm2

- 4500 lumen 4’ shop LED (Sam’s Club) is 23 µW/cm2

- LCD computer monitor is zero

I have some questions and Google is not my friend today. Maybe some of you could enlighten me, and possibly others. When it comes to yellowing from UV I think the above can be used as good data.

-THIS IS THE NUMBER ONE QUESTION. What is an acceptable level of UV light? Of course, we want it to be zero, but that’s not going to happen. I can’t find anything useful on how many µW/cm2 is too much. Is 5 µW/cm2 to much? Or is the UV effect a non issue at 25 µW/cm2? Am I/you killing toys with 12 µW/cm2 (the cabinet lights)? EDIT: I think I just found the answer here. Sorta. It says that 75 µW/lm (microwatts per lumen) is the upper limit. 10µW/lm being ideal. I can't figure out how to convert µW/cm2 to µW/lm yet though. I'm still reading. I need a visible light meter to do the conversion. It's been ordered.

-Is the µW/cm2 specification a good representation of the amount of UV light that the toys “see”. Is it an actual measurement of UV or is it one of those “cheat measurements” that takes one measurement and then corelates it to another?  Is it linear (I suspect it is)? For example, is 10 µW/cm2 going to do half the damage that 20 µW/cm2 will? How about 250 and 500?

-When looking at the LED light sources why doesn’t the µW/cm2 scale with lumens? It’s all over the place. I suspect this has something to do with area. But, testing them all at 3in away should have leveled the playing field? Expect the 4’ shop light. You can’t get 2-3in away from all of the LED’s at once.

-Why is the 825 lumen compact fluorescent putting out less µW/cm2 than the 800 lumen LED? I was under the impression that fluorescent bulbs generated a lot of UV.

-I found the following info on LED's. But, clearly they do put out UV. Or do they? Is the light meter actually measuring UV or something else and then correlating? 

"Light Emitting Diodes (LEDs) are semiconductor devices (materials with electrical conductivity) that can emit a specific spectrum (color temperature) of light depending on the semiconductor material used. LEDs do not emit UV or IR radiation and the light does not generate heat (although the conductor box does). They can supply light for a lower energy cost and have a longer lifespan than other light sources. There is a wide variance in color temperature and CRI and the intensity of the light can diminish over time."

Thoughts?

@Anasazi37

 

Edited September 10, 2020 by sqidd

[Slave IV]

15 minutes ago, sqidd said:

Alrighty smart guys (I’m not saying that sarcastically) I’ve gathered some UV data and need help processing it.

I’m using a Sanctuary UV Light meter. Here are the specs:

-The display is in µW/cm2 (microwatts per square centimeter)

-UV AB Measurement Range:0 to 2999 µW/cm2; It only measures UV AB light power output, but not the wavelength.

-Spectral Detection Range: 240 to 370 nm; Peak point: 352 nm. It does not measure UVC.

-Measurement accuracy: ±4% ±1 digits; Resolution:1.0 µW/cm2

I just collected a bunch of readings from different light sources and I need help making sense of them. All bulb measurements were taken with the light meter 3in from the bulb face.

- Slightly overcast day is 500 µW/cm2

- A sheet of glass (Detolf shelf) knocks that down to 380 µW/cm2

- LLumar UV window film knocks it down to 25 µW/cm2

 - 240 lumen LED bulb (toy cabinet bulb) is 12 µW/cm2

- 500 lumen LED bulb (desk lamp) is 8 µW/cm2

- 800 lumen LED bulb (overhead room light) is 20 µW/cm2

- 825 lumen compact florescent bulb is 17 µW/cm2

- 60w incandescent bulb is 38 µW/cm2

- 4500 lumen 4’ shop LED (Sam’s Club) is 23 µW/cm2

- LCD computer monitor is zero

I have some questions and Google is not my friend today. Maybe some of you could enlighten me, and possibly others. When it comes to yellowing from UV I think the above can be used as good data.

-THIS IS THE NUMBER ONE QUESTION. What is an acceptable level of UV light? Of course, we want it to be zero, but that’s not going to happen. I can’t find anything useful on how many µW/cm2 is too much. Is 5 µW/cm2 to much? Or is the UV effect a non issue at 25 µW/cm2? Am I/you killing toys with 12 µW/cm2 (the cabinet lights)?

-Is the µW/cm2 specification a good representation of the amount of UV light that the toys “see”. Is it an actual measurement of UV or is it one of those “cheat measurements” that takes one measurement and then corelates it to another?  Is it linear (I suspect it is)? For example, is 10 µW/cm2 going to do half the damage that 20 µW/cm2 will? How about 250 and 500?

-When looking at the LED light sources why doesn’t the µW/cm2 scale with lumens? It’s all over the place. I suspect this has something to do with area. But, testing them all at 3in away should have leveled the playing field? Expect the 4’ shop light. You can’t get 2-3in away from all of the LED’s at once.

-Why is the 825 lumen compact fluorescent putting out less µW/cm2 than the 800 lumen LED? I was under the impression that fluorescent bulbs generated a lot of UV.

Thoughts?

@Anasazi37

 

I'm going to say the differences come from brand of bulbs, color temperature and overall specs and quality of them. In order to get better data, you'd want to make as many of those factors equal as possible.

[sqidd]

14 minutes ago, Slave IV said:

I'm going to say the differences come from brand of bulbs, color temperature and overall specs and quality of them. In order to get better data, you'd want to make as many of those factors equal as possible.

Fair point............................and not going to happen.

The biggest question that needs to be answered is how much UV is to much. We have a pretty good idea of what light source emits what at this point. At least roughly. I may have found a half answer while you were reading/responding and I just edited my post. Short version is this:

An article I found (linked above) says that 75 µW/lm (microwatts per lumen) is the upper limit. 10 µW/lm being ideal.  I can't figure out how to convert µW/cm2 to µW/lm yet though. Still reading

Edited September 10, 2020 by sqidd

[MacrossJunkie]

17 minutes ago, sqidd said:

-THIS IS THE NUMBER ONE QUESTION. What is an acceptable level of UV light? Of course, we want it to be zero, but that’s not going to happen. I can’t find anything useful on how many µW/cm2 is too much. Is 5 µW/cm2 to much? Or is the UV effect a non issue at 25 µW/cm2? Am I/you killing toys with 12 µW/cm2 (the cabinet lights)?

 

One thing to remember is that there is no cut off line with how much or how little will cause yellowing. I don't think there is a level where it causes no reaction and then after a certain point it does. It's all "how much over time is acceptable"? It's all cumulative, so if you had a toy exposed to the sunlight, even if you bring it into pitch darkness and leave it there for 10 years, whatever reaction that happened with the exposure to the UV light, even if not visible to the human eye, still remains and does not revert back.

That said, the lower the better, obviously. I think the better question is how much yellowing will a certain amount of UV light cause over a given period of time? That in itself would be difficult to answer too since it depends on the plastic and all the variables that goes into making it.

[sqidd]

4 minutes ago, MacrossJunkie said:

One thing to remember is that there is no cut off line with how much or how little will cause yellowing. I don't think there is a level where it causes no reaction and then after a certain point it does. It's all "how much over time is acceptable"? It's all cumulative, so if you had a toy exposed to the sunlight, even if you bring it into pitch darkness and leave it there for 10 years, whatever reaction that happened with the exposure to the UV light, even if not visible to the human eye, still remains and does not revert back.

That said, the lower the better, obviously. I think the better question is how much yellowing will a certain amount of UV light cause over a given period of time? That in itself would be difficult to answer too since it depends on the plastic and all the variables that goes into making it.

All correct. I'm just dorking out over here (big time) and trying to get a rough gauge for myself and everyone else. I/we don't have the time or money to get this down to science.

I updated the post since you quoted it. I found that the museum standard is 10-75 µW/lm. I was just trying to figure out how to convert µW/lm to µW/lm. Which I did by reading more of the linked article. But, it appears that I would need a standard light meter in addition to the UV light meter to be able to put that number in context. Still reading though. Then I'm going to have to do some thinking. And probably get a light meter. I love tools, so not a huge sacrifice.

[sqidd]

Here is the important section from the linked article. I just ordered a light meter for a whopping $30 so I can finish the conversion.

 

To do your conversion, remember that 1 foot-candle is about 10 Lux

(closer to 10.76). The term "Lux" means "lumens-per-square-meter".

Using a visible light meter, get a light reading in (or convert to)

Lux. There are 1,000 square centimeters in a square meter, so divide

the Lux number by 1,000. You will likely get a decimal number that

represents the "lumens-per-square-cm". Measuring your UV content

with your UVP/UVX Radiometer will give you a UV value in

"microwatts-per-square-cm". Compare the "lumens-per-sq-cm" to the

"microwatts-per-sq-cm" and cancel out the dimensional term. You will

then know the value in microwatts-per-lumen. The "safe range" you

mention (10 to 75 microwatts per lumen) would vary depending on the

level of illumination. If you were looking at a work on paper that

were illuminated at 50 lux, then the "safe range" you are seeking

would be 0.5 to 3.75 microwatts of UV per sq cm. At 100 lux, the

range would be 1.0 and 7.5, etc.

[Mog]

On 9/5/2020 at 11:47 PM, ErikElvis said:

They were hardly handled. And on a shelf in a closet. The rooms vents are closed but it doesn’t get that hot, cold, or humid.   The discoloration is uniform.  The only thing I can think of now is I had a large iguana cage in the room for a couple years. So it was prob pretty warm in there during that time but I can’t imagine over 85. I’ll eventually try to clean them or maybe sit them out in the sun to bake for a couple days to see if that lightens them. 

There’s just so many factors that could cause the yellowing.  

Even if it’s inside a box that allows no light in, the toy could still yellow.  As I mentioned in the other thread, I had a 1/48 Yammie TV Max 1A stored in its box.  The white parts didn’t yellow but the blue parts “yellowed” into teal.

I’m pretty certain the tealing was due to the temperature variations where I stored it.

The other factor could be the height of the shelf you stored it at.  Even if the temperature doesn’t feel too warm in the room overall, it could actually be much warmer the closer your shelf is to the ceiling.

Of course, things you can’t control, such as the air in the room or the chemical composition or manufacturing of the plastic itself, could be the cause of the yellowing.

[BlueMax]

1 hour ago, MacrossJunkie said:

One thing to remember is that there is no cut off line with how much or how little will cause yellowing. I don't think there is a level where it causes no reaction and then after a certain point it does. It's all "how much over time is acceptable"? It's all cumulative, so if you had a toy exposed to the sunlight, even if you bring it into pitch darkness and leave it there for 10 years, whatever reaction that happened with the exposure to the UV light, even if not visible to the human eye, still remains and does not revert back.

Well said, and thank you @sqidd for the measurement data/ knowledge. The objective is then "How to delay the yellowing for as long as possible". 

Although UV undoubtly by itself is a huge factor, I will urge everyone to pay attention to, and attempt to minimise the other contributing factors (plastic composition, direct exposure of bare plastic to air, sustained heat, touch/sweat/oil on skin, high humidity) as well. 

Also, these are not just as standalone factors, but each and every factor can be a catalyst for each other (eg, bare plastic with bad composition, exposed to sustained heat, visible/invisible light spectrum, and frequently handled by bare hands.)

Some things we cannot control, but I am of the opinion that a clear coat, especially a UV cut version, would aid tremendously in buying time before perceptible yellowing sets in.

 

 

 

 

Edited September 10, 2020 by BlueMax

[DewPoint]

2 hours ago, sqidd said:

Alrighty smart guys (I’m not saying that sarcastically) I’ve gathered some UV data and need help processing it.

I’m using a Sanctuary UV Light meter. Here are the specs:

-The display is in µW/cm2 (microwatts per square centimeter)

-UV AB Measurement Range:0 to 2999 µW/cm2; It only measures UV AB light power output, but not the wavelength.

-Spectral Detection Range: 240 to 370 nm; Peak point: 352 nm. It does not measure UVC.

-Measurement accuracy: ±4% ±1 digits; Resolution:1.0 µW/cm2

So I wanted to talk a bit about your light meter.  When talking about specs, the wording becomes very important.  +/- 4% is of the full range.  Thus your light meter is +/- 119.96 and varies an additional whatever your right most digit resolution is.  So all your values are basically in the weeds as your readings are guaranteed to be +/- 121 µW/cm2.  Its tech, so you get what you pay for.  How accurate you really need something is another question.  Its not medical or aerospace equipment, so most likely good enough.

As far as some LEDs go, some manufactures use a blue LED and a yellow phosphor to give you the color of light you are interested in.  The blue light will have a spectrum as well as the phosphor itself.  This may be why you are getting UV reading from your LEDs.  You may have to look more closely at the manufacturer of the bulbs/light strips and type of LEDs used.

[Anasazi37]

My brain hurts reading through the last few posts. I spent way too much time in grad school thinking about this kind of stuff. It's been a heck of a day and I'm likely not firing on all cylinders at the moment, but I'll take a swing at adding what I hope is some useful information to the discussion.

The first thing to do is break down what you're actually measuring with the light meter. If it's reporting microwatts per square centimeter, you're getting an absolute reading for the amount of energy emitted by the light source, within a specific wavelength range (presumably UV), over a standard surface area. This kind of measurement is used a lot for imaging satellites and all kinds of other passive sensing systems that record emitted energy. It's usually a bit more complicated with those, where the standard measurement is watts per meter squared per micrometer per steradian (energy per area per wavelength per solid angle--think of a light cone sent out by a flashlight). Lumen as a unit of measurement is different. It is linked to a human visual model, i.e., what our eyes can see, and values are weighted accordingly, so it's relative instead of absolute. Since we can't see UV, how valid the lumen numbers are for any given bulb in the context of UV is a really good question. There's likely a lot of variability by bulb manufacturer when it comes to UV and the lumen values are likely more accurate for the limited portion of the spectrum that we can see. Makes having a light meter important so you can figure out how much UV you're actually dealing with--regardless of what's printed on the box. And affordable light meters are error-prone. To fix that you'd have to spend tens of thousands of dollars on a spectrometer, so like @DewPoint suggests, roll with the error because it's generally not too bad.

Edited September 10, 2020 by Anasazi37

[sqidd]

20 minutes ago, DewPoint said:

So I wanted to talk a bit about your light meter.  When talking about specs, the wording becomes very important.  +/- 4% is of the full range.  Thus your light meter is +/- 119.96 and varies an additional whatever your right most digit resolution is.  So all your values are basically in the weeds as your readings are guaranteed to be +/- 121 µW/cm2.  Its tech, so you get what you pay for.  How accurate you really need something is another question.  Its not medical or aerospace equipment, so most likely good enough.

As far as some LEDs go, some manufactures use a blue LED and a yellow phosphor to give you the color of light you are interested in.  The blue light will have a spectrum as well as the phosphor itself.  This may be why you are getting UV reading from your LEDs.  You may have to look more closely at the manufacturer of the bulbs/light strips and type of LEDs used.

I hear you on the quality of the tool. I like buying quality tools. In this case it;s not a $1500+ job. Or maybe a job I ever do again.

Interesting info on the LED's. I don't think I'll be able to extract much info from the company. They're "Amazon Junk". It took me forever to get a bulb that didn't burn me out of my office. That's what I ended up with. They're low on lumens compared to most LED's I ran across and a little softer. Does the softness come from a combination of blue LED and a yellow phosphor? What would have the least UV emissions? A white LED? I suppose I could look into some lower lumen white LED's. All that said, my cabinet lights are rarely on. But, I'm an OCD optimizer by nature. I'm sure it will gnaw at me. Thanks for your input.

[sqidd]

4 minutes ago, Anasazi37 said:

My brain hurts reading through the last few posts. I spent way too much time in grad school thinking about this kind of stuff. It's been a heck of a day and I'm likely not firing on all cylinders at the moment, but I'll take a swing at adding what I hope is some useful information to the discussion.

The first thing to do is break down what you're actually measuring with the light meter. If it's reporting microwatts per square centimeter, you're getting an absolute reading for the amount of energy emitted by the light source, within a specific wavelength range (presumably UV), over a standard surface area. This kind of measurement is used a lot for imaging satellites and all kinds of other passive sensing systems that record emitted energy. It's usually a bit more complicated with those, where the standard measurement is watts per meter squared per micrometer per steradian (energy per area per wavelength per solid angle--think of a light cone sent out by a flashlight). Lumen as a unit of measurement is different. It is linked to a human visual model, i.e., what our eyes can see, and values are weighted accordingly, so it's relative instead of absolute. Since we can't see UV, how valid the lumen numbers are for any given bulb in the context of UV is a really good question. There's likely a lot of variability by bulb manufacturer when it comes to UV and the lumen values are likely more accurate for the limited portion of the spectrum that we can see. Makes having a light meter important so you can figure out how much UV you're actually dealing with--regardless of what's printed on the box. And affordable light meters are error-prone. To fix that you'd have to spend tens of thousands of dollars on a spectrometer, so like @DewPoint suggests, roll with the error because it's generally not too bad.

Oh yeah, "bracketing" the problem with REALLY big brackets is the only solution. I like this sort of problem solving though. I may not solve a UV problem, but this has been relaxing.

I ordered a junk light meter. Maybe between my junk UV meter and junk light meter they will cancel each other out and I'll get useful info. Because that's totally how that works.

[Slave IV]

Too many factors and there is still no definite study on all of this. My take is enjoy your toys more, worry less. If your toys get yellow, so what? It’s a color. Now it’s a new color and you get to enjoy the toy all over again as a different color variant. 

[sqidd]

1 minute ago, Slave IV said:

Too many factors and there is still no definite study on all of this. My take is enjoy your toys more, worry less. If your toys get yellow, so what? It’s a color. Now it’s a new color and you get to enjoy the toy all over again as a different color variant. 

I can't even begin to understand how you achieve that level of Zen. I wish I knew how!

That said, I'm not actually worried about the toys. I like figuring things out. It's when I'm my most Zen. Well, it's tied with sliding a roadrace bike through a corner at 100+mph. Which is it's own problem to solve.  I've started in on stuff like this and the next thing I know it's 12hrs later and the sun is coming up. And, figuring this out could have a practical upside. Beats doing a cross word puzzle.

[Slave IV]

10 minutes ago, sqidd said:

I can't even begin to understand how you achieve that level of Zen. I wish I knew how!

That said, I'm not actually worried about the toys. I like figuring things out. It's when I'm my most Zen. Well, it's tied with sliding a roadrace bike through a corner at 100+mph. Which is it's own problem to solve.  I've started in on stuff like this and the next thing I know it's 12hrs later and the sun is coming up. And, figuring this out could have a practical upside. Beats doing a cross word puzzle.

Solving problems is great, I agree! The thing is, this is an issue that after decades of people collecting toys, there is no answer. There are simply too many factors.

[sqidd]

8 minutes ago, Slave IV said:

There are simply too many factors.

I am the factor slayer!!!!

The best gig I ever had (until I got sick of the travel) was being a suspension engineer/setup guru. It's a problem that never has a solution a zillion variables and changes constantly. I loved it!

[Sanity is Optional]

I wonder if I could borrow the spectrometer from work, some of our stuff operates in the microwatt range so it's fairly sensitive.

[Slave IV]

11 minutes ago, sqidd said:

I am the factor slayer!!!!

The best gig I ever had (until I got sick of the travel) was being a suspension engineer/setup guru. It's a problem that never has a solution a zillion variables and changes constantly. I loved it!

Do it! I’d love to see the definitive answer. 

[kkx]

50 minutes ago, Slave IV said:

Too many factors and there is still no definite study on all of this. My take is enjoy your toys more, worry less. If your toys get yellow, so what? It’s a color. Now it’s a new color and you get to enjoy the toy all over again as a different color variant. 

Many people claim that such attitude will make you live longer! Good advise.

I have a yellowed YF-30. Trying to solve the problem by making it not a problem. Not sure yet how successful I am. Trying hard to control the urge to paint it white.

Edited September 10, 2020 by kkx

[Slave IV]

6 minutes ago, kkx said:

Many people claim that such attitude will make you live longer! Good advise.

I have a yellowed YF-30. Trying to solve the problem by making it not a problem. Not sure yet how successful I am. Trying hard to control the urge to paint it white.

Yeah, I just don’t get what the big deal is. Turn up the yellows on your tv next time you watch Macross...there you go, now you have a screen accurate Valk again!

Oh wait...most the toy Valks were never screen accurate colors to begin with. Throw them all out!....onto my doorstep.

[MacrossJunkie]

Or stock up on decals, then when your toy looks like it's been soaking in pee, time to repaint it and apply those decals! 

[Lolicon]

How much could it possibly cost to keep each valk in a vacuum-sealed, temperature & humidity controlled display case? 

[ErikElvis]

I have a Uv meter for my tortoise bulbs. I should pull it out to see what it registers in my house with the outside light coming in. I’m willing to bet it won’t register much if anything at all but will do it out of curiosity. I think it only registers uvb though. 

Edited September 10, 2020 by ErikElvis

[chyll2]

3 hours ago, MacrossJunkie said:

Or stock up on decals, then when your toy looks like it's been soaking in pee, time to repaint it and apply those decals! 

yeah, a quality white paint will takes ages to yellow.

[tekering]

I'm neither a math geek nor an engineer, so I don't have much to contribute to the discussion beyond my own experience:

As a child, I took good care of my toys; I removed and discarded the packaging, of course, but I rarely lost accessories or broke anything.  As a teenager, I displayed my toys with pride -- particularly the Takatoku or Gakkens -- but they were exposed to sunlight, because I didn't know any better.  The first toys to show obvious signs of UV damage were my Kenner Star Wars figures...

Some, like my original Luke Stormtrooper (left), were very expensive to replace.  

For the most part, though, discoloration wouldn't be visible until the figures were removed from sunlight and put into storage, or packed for moving.  After a period of weeks (or months), a very unpleasant surprise would be waiting when they got unpacked.  

As an adult collector, anything I consider of particular value (or anything molded in white plastic specifically) never sees a glimmer of UV light.  Windows are completely boarded up in my toy rooms, doors remain closed, and every pre-existing light fixture has been replaced with LED lamps, with white (so-called "cool") LED bulbs used exclusively.  Thanks to these precautions, no figure I've bought in the last two decades has shown any discoloration at all, despite the hot and humid Japanese summers (and very little ventilation).

However, we all know that plastics can be unpredictable, and sometimes we don't know what conditions our toys were exposed to before we acquired them in the first place.  This is a particular concern for collectors like @sqidd, who buy a lot of product on the secondary market.  For me, my biggest problem is not with the figures themselves, but with the clear blisters they're packaged in; for example, I have Star Wars figures from the same wave, bought at the same time, from the same location, having been displayed for years in the same environment...

...yet most have perfectly clear blisters, while others have yellowed significantly.

Sometimes it's simply unavoidable.  

[MKT]

1 hour ago, tekering said:

For the most part, though, discoloration wouldn't be visible until the figures were removed from sunlight and put into storage, or packed for moving.  After a period of weeks (or months), a very unpleasant surprise would be waiting when they got unpacked.  

Bingo! Because this describes about roughly same experience I had many years ago. I had a couple of figures being out in a room with indirect but still bright ambient light for about couple of years, and then one day I noticed they started to turn just ever so slightly yellow. I removed them to another room that have no sunlight at all, and in just a matter of short 1-2 months, it yellowed significantly.

@BlueMax mentioned on previous page that exposing yellowed items back into ambient light reverses the yellowing to some degree. So it seems UV light both causes & reverses yellowing.

Now I am sitting here wondering, perversely, if I should just have left my two yellowed items out in the bright room. Yes, they would continue to yellow, but perhaps not as rapid as if I removed them into a dark place, if that makes sense at all..