Color Theory

[Barry Daniels]

Yesterday, I was mixing some TransTint dyes to make the new bracing in my Martin resto/mod project look not so new. I added two drops of brown and one drop of red/brown to some alcohol and sprayed the inside of the box. The red/brown was probably not a good idea. It turned the spruce bracing sort of pink. So I started trying to remember color theory to see what color will "kill" red. I could not find a good reference online other than somewhat vague descriptions of Additive and Subtractive Color Theory, the best one being on Wikipedia. But what I need is a color wheel to post in my shop to refresh my memory whenever I break out the dyes. I created the attached chart and wanted to see if anyone sees any errors in my understanding of this.

To begin with, I think that adding two different colored transparent dyes to get another color falls under the Subtractive Color Theory. My most memorable example of this was in 3rd grade when I was coloring a picture of the sky. The perimeter around the yellow sun bordering the blue sky turned bright green.

To my mind, there are two situations. The first is where I want to get a dye color that I don't have in stock, by mixing two other colors. The second is where I want to neutralize or kill a color that has already been applied, by laying down another transparent dye.

I downloaded a subtractive color wheel and marked up my understanding of how it works. Comment if you seen any errors, please.

[Brian Evans]

My understanding is you can't remove a primary colour, you can only make it another colour, usually a darker colour. If you added green to red, in your example, you'd get somthing in between them, and in theory - black. Green is the addition of blue and yellow, two primary colours, and adding the third primary - red - should get black. The subtracting bit is because colours reflect light, and subtract or absorb their colour. But to be honest this is too long ago, and physics class at that! There are additive colours when the source is a light, and subtractive colours when the source is a thing reflecting light, and red/yellow/blue and cyan/magenta/yellow. I found out the hard way one night that if you write things down in red grease pencil, and when it gets dark try to read them with a red light, you get nothing. Red grease pencil only reflects red light, and a red light has a filter that removes all red light.

In your example, you add kind of purple and orange to try to get red. Can't be done, you cannot add colours to get a primary colour. In the second example you add two primary colours - blue and yellow - to get a secondary colour - green. Perfect, works every time. You can't make red, yellow or blue but in theory you can make all other colours from them.

[Bob Gramann]

When I have dyed wood, it never penetrates as deep as I would like. Perhaps a little superficial sanding would solve your problem?

[Barry Daniels]

I ended up mixing yellow and blue to get green and then sprayed that on to kill the red. I also added a some tobacco brown which is kind of a greenish brown. It worked out pretty well. It gave me the dirty, aged wood effect that I was looking for. Thanks for the explanation Brian. That helps.

The first photo is the pink bracing and the second is the final result. The un-dyed top bracing is included for comparison.

[Alan Carruth]

Brian Evans wrote:
"Red grease pencil only reflects red light, and a red light has a filter that removes all red light."

I think you meant "removes everything except red light" The white paper would look as red as the grease pencil marks, so they'd be invisible.

When I was in the Navy they had a daily 'green sheet': a schedule for all the days events that went out early every morning, printed on green paper. They would print one on white paper for the bridge. One day the guy from the print shop brought a green one up to the bridge by mistake. They still had the red lights on, which preserve night vision, and the green paper looked black. He had to high-tail it back to the print shop 'way below decks for the white one.

[Dick Hutchings]

I really like the outcome. You have me thinking

[Barry Daniels]

My understanding is you can't remove a primary colour, you can only make it another colour, usually a darker colour. If you added green to red, in your example, you'd get somthing in between them, and in theory - black. Green is the addition of blue and yellow, two primary colours, and adding the third primary - red - should get black.

I think this theory is correct as it applies to pigmented, opaque colors. But when using transparent toners, there is a different outcome. Two toners added together will never result in black. A toner of green mixed with red will sort of neutralize each other, maybe giving a light transparent gray. (May have to do another experiment).

In my project, the green toner definitely got rid of the pink shade on the spruce braces. And that seemed to have allowed the brown to come out and be the dominant color.

[Barry Daniels]

I've been doing some more research on this issue and want to provide a few links to useful stuff I found. Here is a really good YouTube video on touch up. This is a technique that I have been trying to teach myself for many years but I was using the wrong materials. I was using a base of white or tan oil-based enamel and then mixing in color stains or UTCs. Then brushing it on with an artist's brush. Problem is the enamel is an opaque paint and it is hard to make the repair blend in. Never really got the results I was after. The guy on YouTube uses shellac as the base and mixes in Mohawk dry stains called Blendal. I bought some this morning and will be trying it out. Here is the link:

Touch-Up

[Barry Daniels]

I also found a color wheel specifically designed for wood finishing.

Color Wheel

[John Tuttle]

Instead of mixing up a color batch for aging the look of new wood, have you tried Potassium Permanganate in water? It's an oxidizer that I use often to achieve the darkening caused by time and exposure to air. Kind of like speeding up time. You can dilute to suit the amount of oxidizing you need.

[Alan Carruth]

There are various ways to color the wood, and they often give nicer results than stains or colored varnish.

Any wood that has tannin in it will probably darken with exposure to ammonia. I'm fuming a white oak guitar now; it produces that 'Golden oak' color. Locust and Osage orange also fume well, as does mulberry. It's often worth a try on an offcut. I'm told that a wipe with vinegar afterward will mitigate any greening tinge: I'll find out soon. That tends to fade anyway under finish, in my experience.

Cherry, and maple (to a lesser extent), will darken nicely when wiped with a mild lye solution. Since I heat the shop with a wood stove I have hardwood ashes to make my own lye, and that seems to work better than commercial sodium hydroxide. Use a really mild solution, and repeat until you get the color you want.