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| A Note on Color Matching https://www.rypn.org/forums/viewtopic.php?f=1&t=43853 |
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| Author: | jayrod [ Fri Oct 25, 2019 10:53 am ] |
| Post subject: | A Note on Color Matching |
Curiosity killed the cat. Rather than bury it in the sticky above I'll toss this out here for general consumption. While chasing down some other color codes, I posed a question to my contact at the PPG Coatings Innovations Center R&D department concerning the use of Munsell and CIE L*A*B* color space numbers to produce accurate colors. His response: "You can use the color space numbers to get close, but the color instruments and software to create the numbers use different techniques and math to generate the data. Since it’s not universal, you get some variation in output when you try to plug the numbers back in to generate a color formula". His reference is to the equipment used, not to the color space systems themselves. Still, the definitive way to get a match as close as technically possible to the original color is to have a physical sample to scan and to compare by your preferred supplier's lab. I will reiterate that with all the variables in the original paint mixing, application, weathering and the changes in pigments, carriers and dryers over the years, an exact match in color and sheen to the obsolete formulations will always be elusive and the results subjective at best. In other words, don't beat yourself silly trying to achieve absolutely perfect matches. I'll add this tidbit in the next update to the to the cross reference accessible from the sticky at the top of this forum. As always, if you have any paint info not in the list, please forward it to me and I'll get it in the list. |
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| Author: | Dennis Storzek [ Fri Oct 25, 2019 6:19 pm ] |
| Post subject: | Re: A Note on Color Matching |
Eric, Interesting comments, and they brought to mind a pet peeve of mine concerning color matching. I don't doubt that PPG has state-of-the-art equipment, and that your contact knows of what he speaks. But I have heard numerous times, not so much here, but on model forums, to "just take your sample down to the local big box store and get it scanned." Never mind that the scanner has likely never been calibrated, and isn't expected to produces matches better than an 'industrial match', which basically means the color is in the same general area of the spectrum as the target. I had an interesting experience a couple years ago. For those who don't know me, my livelihood for the past thirty years has been manufacturing model railroad hobby products. A couple years ago it was postulated that the rather pricey waterborne coating we used on the models was closely related to a product made for the home improvement market, and we should just buy paint at the local outlet, having them scan and match our standard colors. So I prepared some color chips and took a trip to town. Long story short, they did an excellent job matching the oxide based freight car colors, but I wanted to see how they would do with a bright yellow, such as reefers were traditionally painted. Their match looked like... well... puss, or that stuff you occasionally find in the grandkid's diapers. Given the bases and tinting colors supplied to make house paint, they simply couldn't make a clean primary color. Worse yet, the kid that was running the paint department insisted it was a "perfect match. " How did he know? The machine had said so. Not saying computer matching can't give good matches, but simply pointing out that not all systems are created equal. |
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| Author: | jayrod [ Fri Oct 25, 2019 7:25 pm ] |
| Post subject: | Re: A Note on Color Matching |
And this, in the same vein... When purchasing any custom mixed paint in multiple cans or buckets, always purchase empty spares to mix all the cans together in equal proportions or you'll have a major "uh oh" moment when switching to the next can. Don't ask how I learned this very valuable lesson. Dennis: I've worked with your partner in crime on some artwork and colors so I understand the gyrations you guys sometimes have to go through. However, I can't imagine what kind of paint a big box store would have that had pigment ground fine enough or that wouldn't peel off. Just curious. |
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| Author: | kew [ Fri Oct 25, 2019 8:22 pm ] |
| Post subject: | Re: A Note on Color Matching |
Dennis Storzek wrote: but I wanted to see how they would do with a bright yellow, such as reefers were traditionally painted. Their match looked like... well... puss, or that stuff you occasionally find in the grandkid's diapers. Baby poo yellow? That's the name we give the stuff ("officially" called navy dressing) we paint the canvas carriage roofs on our 12" to the foot models! There's just been a book published here about New South Wales Railways (Australia) colour schemes, https://arhsnsw.com.au/product/nsw-railways-in-colour.The authors gathered a lot of samples from places on rolling stock still in existence that had been covered up for decades (ie not exposed to sunlight) to establish what colour they were, but dodged the question of colour spaces. A pity since it would make our task of painting carriages in "authentic" colours a bit easier if we had a code to give a match. |
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| Author: | Dennis Storzek [ Sat Oct 26, 2019 8:24 pm ] |
| Post subject: | Re: A Note on Color Matching |
jayrod wrote: Dennis: I've worked with your partner in crime on some artwork and colors so I understand the gyrations you guys sometimes have to go through. However, I can't imagine what kind of paint a big box store would have that had pigment ground fine enough or that wouldn't peel off. Just curious. You'd be surprised. Olympic Overcoat solid color 'stain' has actually morphed into a light bodied waterborne acrylic with exceptional hiding and adhesion properties... as I write this I am looking at a piece of galvanized pipe railing I painted with this material seven or eight years ago that is still holding the paint. What killed the experiment was problems with a longer dry time than we were used to. |
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