Yellowing - How To Prevent?

[sqidd]

9 hours ago, Anasazi37 said:

Okay, that's both disturbing and funny. Based on your previous post, it sounds like you have a UV radiometer/light meter with the following 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

Unless a bulb manufacturer gives you information about the amount of UV light the bulb is sending out, you'll have to make a direct measurement. The specs for the meter claim that it's accurate to within 4%, so you could take the reading you get and create a range for your bulb, with your reading minus 4% on the low end and your reading plus 4% on the high end. And you're getting a more general estimate for all of UVA/B, what is sometimes called an integrated value or a band pass value. The sensor gathers in light across a broader range of wavelengths and then averages all of that to produce a single value, so any specific behavior of UV light at specific wavelengths is lost. That's why lab-grade spectrometers cost so much. Not only are they calibrated, but they also make multiple measurements over smaller chunks of the range, sometimes hundreds or thousands of them, which can then be used to create a continuous line that looks something like this, which I randomly grabbed from the results of a Google Image Search:

So, back to your question about how much UV light is too much and can you convert the output from your UV meter into something useful. I would argue that µW/cm2 is a useful measurement because it's absolute and describes how much energy is hitting a surface, which is exactly what you want to know. The technical term for it is irradiance:

https://en.wikipedia.org/wiki/Irradiance

Irradiance is widely used in the scientific and engineering communities, so you're on solid ground there. So, I think it's more about taking values used by communities who worry about UV light damaging stuff and converting them to irradiance, but let's put a pin and that in see what they actually do. It does seem like the cultural heritage preservation crowd, i.e., museums, has thought about this quite a bit. I found what looks to be a pretty useful resource from the Canadian Conservation Institute (likely far more credible than a random reply on a message board):

https://www.canada.ca/content/dam/cci-icc/documents/services/conservation-preservation-publications/canadian-conservation-institute-notes/2-2-eng.pdf

It opens by saying that no one outside of the museum world thinks about UV in relative terms, which is what that µW/lumen measurement is: a ratio between light you can't see and light you can. Hence my previous comment about how you can't take a visible spectrum, lumens-only measurement and convert it to one that is relevant for UV, however if you have instruments that can measure both (I forgot you had both), you can create your own µW/lumen measurement. There's an entire section in the article on absolute UV values, which was nice to see. Probably a hat tip to radiometry nerds like me.

Based on that article, it does seem like 10-75µW/lumen is the acceptable range, even if the approach is wacky. What matters is that museums have been using this approach for a long time and the numbers hold up, so make use of the numbers. Let's do some math:

1 Lux = 1 lumen/m2

1 m2 = 10000 cm2

Visible light meter reads 4600 lux

UV meter reads 12 µW/cm2

The equation given in the paper looks like this:

UVab = (L x UVr) / 1000, where UVab is reported as mW/m2, but those aren't the units we want. So, this is what you do:

µW/cm2 = (lumen/m2 * μW/lumen) / 10000

So, you end up with 12 = (4600 * UVr) / 10000, where UVr = 26.09 µW/lumen

A value of 26 is in the acceptable range, so my best guesstimate is that your bulbs are fine.

The gif is from the movie Scanners. Th best mind blown gif ever!

Thanks for the legwork! It baffles me that considering how big the art industry is that there isn't a more concise and easily measured system. Why not a simple UV number taken with a UV meter? Seems pretty simple assuming I'm not missing something. You would think that one billionaire with an incredible collection would commission the testing to see what the limits are. I know I would. Then I would probably turn it into a business that asses the environment of art collections then brings them in line with the acceptable range. There is a ton of potential money to be made there. Not from goofballs like us. The FU money crowd. Hmmmmmmmmmm. That sounds a lot easier than what I do now. And I've been getting bored. Maybe it's time for a change.

I blasted an email out to a bunch of bulb suppliers that advertise low UV bulbs today. I'm going to get some samples and test them. Not because I'm necessarily concerned. But because I'm curious.

I'm wit Tekering (it's his fault for getting me started on this). I'm all about the zero tolerance policy. UV isn't the only thing I've gone after. The temp my toys are at is never outside the 60-70degF range, The boxes 10deg less. They never see more UV than the cab lights (not even close) and those are not on much. Now to figure out that oxygen thing......

[Slave IV]

9 minutes ago, sqidd said:

The gif is from the movie Scanners. Th best mind blown gif ever!

Thanks for the legwork! It baffles me that considering how big the art industry is that there isn't a more concise and easily measured system. Why not a simple UV number taken with a UV meter? Seems pretty simple assuming I'm not missing something. You would think that one billionaire with an incredible collection would commission the testing to see what the limits are. I know I would. Then I would probably turn it into a business that asses the environment of art collections then brings them in line with the acceptable range. There is a ton of potential money to be made there. Not from goofballs like us. The FU money crowd. Hmmmmmmmmmm. That sounds a lot easier than what I do now. And I've been getting bored. Maybe it's time for a change.

I blasted an email out to a bunch of bulb suppliers that advertise low UV bulbs today. I'm going to get some samples and test them. Not because I'm necessarily concerned. But because I'm curious.

I'm wit Tekering (it's his fault for getting me started on this). I'm all about the zero tolerance policy. UV isn't the only thing I've gone after. The temp my toys are at is never outside the 60-70degF range, The boxes 10deg less. They never see more UV than the cab lights (not even close) and those are not on much. Now to figure out that oxygen thing......

Jeez! You have a walk in freezer you are storing your stuff in?

[sqidd]

1 minute ago, Slave IV said:

Jeez! You have a walk in freezer you are storing your stuff in?

 My house is never above 70 in the summer and I keep it at 65 in the winter. During spring and fall it gets cooler at night when the windows are open. The basement where the boxes are runs 10deg cooler. The basement is bone dry. Humidity is 30-65%. The 30 is in the dead of winter. Despite having dual humidifiers I can't get it any higher.

I'm going to design cabs that pull a vacuum, block all UV light and are lit by near zero UV bulbs. I'll make millions!!!

[Slave IV]

45 minutes ago, sqidd said:

 My house is never above 70 in the summer and I keep it at 65 in the winter. During spring and fall it gets cooler at night when the windows are open. The basement where the boxes are runs 10deg cooler. The basement is bone dry. Humidity is 30-65%. The 30 is in the dead of winter. Despite having dual humidifiers I can't get it any higher.

I'm going to design cabs that pull a vacuum, block all UV light and are lit by near zero UV bulbs. I'll make millions!!!

Haha, nice! That probably wouldn’t even be that hard to do. 

[derex3592]

10 hours ago, sqidd said:

 My house is never above 70 in the summer and I keep it at 65 in the winter. During spring and fall it gets cooler at night when the windows are open. 

 

 

If you're married.....just wow....I can only pray for that cold in my house and windows open...

[slide]

18 hours ago, sqidd said:

 My house is never above 70 in the summer and I keep it at 65 in the winter.

and you say you're NOT Canadian... eh?

[sqidd]

7 hours ago, derex3592 said:

If you're married.....just wow....I can only pray for that cold in my house and windows open...

She has sweatshirts.

31 minutes ago, slide said:

and you say you're NOT Canadian... eh?

I'm only 40min from the border. So almost.

[sqidd]

I don't know if these started off as the same color plastic. They're not now. If they started off the same color there is a great example of formulation being a factor.

 

[ErikElvis]

I didn’t think about it before but I had cats in my spare bedroom before I started dumping all my toys in there. My in box jet fire , shuttle tydirium, and b wing all yellowed as previously mentioned. I think it may have had something to do with the cat piss odor.  Maybe ammonia like previously mentioned. Looking on eBay that shuttle tydirium is not easy to replace.  Well no chance in making them worse so any ideas on bringing the natural color back?

[sqidd]

5 hours ago, ErikElvis said:

I didn’t think about it before but I had cats in my spare bedroom before I started dumping all my toys in there. My in box jet fire , shuttle tydirium, and b wing all yellowed as previously mentioned. I think it may have had something to do with the cat piss odor.  Maybe ammonia like previously mentioned. Looking on eBay that shuttle tydirium is not easy to replace.  Well no chance in making them worse so any ideas on bringing the natural color back?

There is a thread with info on getting the white back. It's called something like "You're yellow".

[vladykins]

So my yellowed Yamato 1/60 v1 Hikaru that was in pretty sad shape I've been starting on moving him to an Alaska Base custom. I have to put on another coat and clean up a *lot* of the lines on there, but he's already starting to take shape. Even needing more work, it is way better than the crazy yellow thing I had before. Once I finish tidying up the primary colors, I'll add in some detailing.

Knees look a little odd from this angle- they'll look better once I tidy that up.

Edited October 11, 2020 by vladykins

[Vintage Fanboy]

Can we use Acrylic Sprays (Varnish) to prevent white ( - painted) toys from getting aged (yellowed)? And if yes, will it stick to any glossy paints (of particularly on DX Superalloy products)?

[David Hingtgen]

I suspect it would help against UV-based yellowing from sitting near a window, but considering the valks I've had turn yellow in a windowless room/inside their box, "being exposed to air/oxygen" is still a factor, and I'm not sure a clear-coat would be "air-proof".