I have been experimenting with ARTI water-based dye concentrates for 6 months or so, and mostly with great satisfaction. They have strong colors, spray well, etc. Four months ago, I made a bunch of color samples and put them in the shop windows - in direct sun for most of the day. The reds and yellows have held up well, but the blues and, to a lesser extent, the greens are gone. Only a gray shadow remains.
I have two questions:
First: Is this typical of dyes? Are there other manufacturers who have better results in the area of lightfastness? I really like the transparency of the dyes.
Second: Are there top coats I could use to prevent this? The samples are top-coated with 2 coats of Duravar. Since then, I have been exploring 2k polyurethanes and see that some manufacturers provide UV inhibiting additives: do these work? Any advice would be appreciated.
From contributor C:
This experience is totally typical of dyes. Some of the aniline (water based) dyes are significantly more durable, but for real dependable tinting you have to go to pigments. Pigment based stains and glazes can be extremely durable, but you have to know which ones you are using, because their performance varies widely and can only be evaluated in regard to each specific pigment.
Generally speaking, it is difficult to get long lasting yellows, and there are only a few reds which hold up well (and they are the more expensive ones). There are quite durable pigments available in most of the other colors today. Unfortunately, many manufacturers are not very motivated to use the most durable pigments in their products. Those manufactures who use the cheaper pigments rarely reveal that fact on their labels. Sometimes the manufactures who use top quality pigments will make that information available (but not always). For the most critical applications, it’s advisable to formulate your own stains and glazes so that you can control the specific pigments used, and thus the longevity can be accurately projected.
Also, about the top coat question, I have noticed a difference between finishes that have UV absorbent materials, and ones with UV inhibitors. The second seems to be stronger.
There are organic UV additives that you can use with your finishes to help reduce or slow the fading a lot. Your supplier may have a UV additive for the finishes you use, or you can switch to a product that includes them. You could also try purchasing UV protective additives and add them to the finish yourself.
Micronized pigments are another option as others have pointed out. The particles are so small they behave like a dye as far as coloring goes. I don't do much work in green, but do some work with blue. I use a combination of dye and pigment to get the color, and it holds up well. It's never a good idea to expose furniture grade finishes to direct sunlight.