Lightfastness of Dyes and Stains

      Finishers discuss the differences between dye and stain chemistry in this thread. The differences between dyes and pigments include varying resistance to light degredation. June 28, 2005

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.

Forum Responses
(Finishing Forum)
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.

From contributor S:
I use dyes on a lot of our jobs and being lightfast is a big issue with our shop. I have tried several, and haven't found any better than Mohawk 520's. They are acetone based and low voc. I do believe they can be cut with water.

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.

From contributor M:
ML Campbell's dyes are textile grade (used to dye clothes) and are supposed to be more lightfast. As far as UV inhibitors, I am told that this additive is very expensive, and tends to expire over time, so manufacturers tend not to use enough to be greatly effective.

From contributor C:
The new dyes are not anilines, they are actually micronize pigments. They are sometimes referred to as anionic dyes. There are a lot of names giving to these pigmented dies’s and they originally did came from the textile industry. They are definitely better for lightfast, and have excellent transparency.

From contributor J:
I'm not all that up on the technical aspect of dyes, but I do know that the blues, purples, and violets do fade out faster than the other colors. The new dyes they're coming out with today are a lot better than the ones made 5-10 years ago as far as light-fastness. I like using the metalized acid dyes because I feel that these give me the best hold out. Try using the alcohol based ones instead of the water dyes - they tend to last longer. Also, if possible, try and keep direct sunlight off of the dye piece when it's done.

From Paul Snyder, forum technical advisor:
Metalized aniline dyes are the most lightfast. No matter the type of dye, blues and greens are the least lightfast of all the colors. So your test results are typical of good dyes.

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.

From contributor M:
What is the difference between dyes and micro fine pigments?

From contributor C:
To contributor M: Most dyes completely dissolve in some type of solvent. The pigmented particles, regardless of their size, will never dissolve.

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