Updated: Nov 3, 2020
Short answer: No
What is Mica Powder?
Mica Powder is a natural substance, it is a stone which has sparkly flecks throughout it. When you grind Mica into a powder it results in a mica powder which is sparkly and looks a bit like a very fine glitter. You can use mica powder to achieve a pearl-like effect or a metallic finish. Mica powder come in an assortment of colors. (source is resin-expert.com) Mica powder has been used for hundreds of years, dating back to prehistoric times. It has been documented that mica powder was known to the Aztec, Indian, Roman, Egyptians, Chinese and Greek civilizations.
The use of Mica Powder can be seen as far back as cave paintings found in the Upper Paleolithic period.
The Pros and Cons of Mica Pigments
If you source mica pigments, I recommend that you directly ask the supplier if the mica is ethically sourced. This is something I always make a point of doing with new suppliers that approach me or likewise. Some suppliers have this information available on their websites. Please be mindful that some do not so it is your responsibility to ask if you are wishing to purchase it.
For my experiment, I used two different mica pigments. An Aztec Gold and an Orange/Red with an iron oxide base. I used the same binder and amount, same paint brush and paper. I timed each mulling cycle to be the same for each pigment. I photographed the pigments next to each other in the same light/time of day.
According to my experiments and the results, I would conclusively say that there is no need for mulling your mica pigments. Why spend ALL that precious time of yours for the results to be rendered about the same and/or a different hue to the one originally intended?
Popular question: What if there is an iron oxide base color ? I discovered that not mulling it did not affect rubbing off or it's dispersion. I tested the palette knife mixed mica and it did not rub off the paper and the hue seemed even.
Did the color change with an iron oxide base? Yes! There was a difference with the iron oxide based mica pigment with regards to the hue. It appears that it reflected the light differently and therefore the color appeared different. The non iron oxide based pigment did not appear changed in hue.
If these are the results above then why mull? It does not affect the hue markedly and it does not rub off. It dispersed evenly with a palette knife. So why?
So, why do makers mull their mica pigments in the first place?
I can only assume this because I do not mull mine. But I would suppose that it started with one maker and then this influenced future makers thereafter perhaps? Perhaps the makers who mull their mica do so because they originally thought that mica and matte pigments are one in the same whereas they are not the same. Matte pigments are different to mica pigments.
Mica is a natural stone mineral with shiny flakes. When mica is ground into a powder, you get mica powder. Mica powders are therefore sparkly, sort of like very fine glitter. Pigment powders are ground-up colors, sort of like powdered colored chalk. Pigments are the actual colors themselves and have names such as ultramarine blue, cadmium red, yellow ochre, and titanium white. (Source is thebluebottletree.com)
Results of a poll and question via instagram.
Same = 97 votes Different = 79 votes
Number 1 is more red and Number 2 is more pink.
Mostly same hue but different light.
Right is lighter
#1 looks slightly darker but may just be the lighting!
Left seems darker.
Maybe the one on the right is a bit warmer. But in the picture I can't really see a difference.
I said same as the tiny differences wouldn't be enough for me to class them as two separate entities.
Not a stark difference, but 1 is a slightly darker shade than 2? And a little more red.
Hard to say because of the light, but I feel like the left is more dark/red.
They look the same although I think the left one is a little richer and darker of color.
Hard to say - either the same with a little difference in lighting OR slightly different.
The light reflects the color differently. Almost looks like being a shifter.
2 is more orange-iy, 1 seems more reddish.
They look like two copies of the same sketch slightly different but not enough to say they aren't.
Light looks from different angle.
2 looks slightly more light and yellow.
#2 is not as dense.
Left looks a little more reddish, but if I hadn't searched for it I couldn't tell - could be wrong.
It may be the light? The outer shapes look more pigmented, especially the rectangle.
Lighting is different.
1 seems deeper, richer.
I don't know how to explain it, but I do see a slight difference. Maybe the base pigment? I don't know.
The only other factor I have not mentioned in this article is that because mica particles have a specific role to play in their ability to reflect the light, there is the suggestion that mulling could potentially further grind these mica particles further into smaller micron particles. It would then mean that if this does occur, then this would explain why there could be a change in hue with certain mica pigments. This could also explain why you might notice differences between makers even though they use the same pigments. It is entirely your decision which maker you choose to support however, it would be such a time saver for the maker to not have to mull mica at all don't you think?
Please feel free to comment and please no mention of other brands/makers. Let us be mindful and kind to one another.
Please note that I have been making my own watercolors for two years and have worked with as many as 300 or more pigments in this time. I have worked with numerous brands, both matte and mica, chameleon, iridescent and lake/dye pigments. I am not an expert but I do have a lot of experience to share. with you.