Evening out mahogany color variations

[Matthew Joe]

Hello--I recently purchased about 75 bf of mahogany. Not sure what particular species (purchased from CL). The first few boards that I planed had a beautiful natural dark color and were devoid of knots, swirling figures, etc. Some of the other boards have been noticeably lighter and have more defects and variations in figure. See pictures below. Are these just sapwood variations? Is this normal?

I need the colors to match. What can I do to accomplish this?

Thanks!

[Faust M. Ruggiero]

Matthew,
This is why most old mahogany pieces are so dark. Mahogany can vary from very light to rich dark brown. Unless you want to heavily darken the piece, I suggest picking your stock for color match before you begin your build.
fmr

[guy knight]

there is a way to darken them using a chemical i think drain cleaner is the one

[Peter Quinn]

Check the FWW site for an article by Peter Gedrys. He's got a great approach to finishing mahogany that I witnessed first hand as a student in his class on color theory and dye stains. Basically he starts with a lemon yellow wash to even everything out, then moves on to a medium brown color, then on to a vandyke brown that has a lot of that deep red associated with older mahogany. It won't obscure the gross variations in grain pattern but it does an amazing job equalizing color variations, and it makes the wood glow. I watched him take boards from across the mahogany color spectrum that I brought in as samples and make them all look like they were cut from one board.

Another powerful tool is the sun. Letting dark woods like mahogany get a little tan tends to push them towards a more equal brown color. There is no guarantee which makes constructing a piece with boards with great variations a little unnerving.

The chemical that made old mahogany deep red brown was potassium dichromate, not drain cleaner. Please do not soak your mahogany in drain cleaner. There is a fair amount of info on potassium dichromate on the web, but I can't help much there as I have never used it.

[Frank Drew]

Matthew,

Your best course will be to experiment on scrap pieces with a couple of different coloring methods... dyes, stains, maybe, etc.. I like dichromate of potash on mahogany; it's a water based chemical dye, so, after final dry sanding, and before applying the dye, wet your wood with some water to raise the grain and then sand off the fuzz when it's dry; that way the water in the dye won't affect the wood too much and you won't need to sand the dyed wood (some people have pointed out the hazards of potassium dichromate's sanding dust.)

I never liked finishing enough to get into it to the extent that Peter's fellow does, but also never felt the need to. I like the results I got with minimal interventions.

[David Keller NC]

Hello--I recently purchased about 75 bf of mahogany. Not sure what particular species (purchased from CL). The first few boards that I planed had a beautiful natural dark color and were devoid of knots, swirling figures, etc. Some of the other boards have been noticeably lighter and have more defects and variations in figure. See pictures below. Are these just sapwood variations? Is this normal?

I need the colors to match. What can I do to accomplish this?

Thanks!

No, that's not sapwood. Mahogany sapwood is rarely seen in commercial lumber stocks - it's removed at the milling site.

What you're seeing is normal color variation in either south american or african "mahogany" (actually, african "mahogany" is utile or khaya species). Based on the ribbon-striping, I'm guessing what you have is african. Anyway, you've a number of recourses to get the boards to match up. Most of these involve darkening the wood quite a bit. You can use an aniline dye (either water or oil-based), but you can also chemically transform the wood with nitric acid and heat, potassium dichromate and even tannic acid/ammonia fuming. If you choose to go with this latter route, be aware that potassium dichromate is a wicked carcinogen, and nitric acid can be quite dangerous in its more concentrated forms.

One other possibility not yet mentioned is to bleach all of the wood with oxalic acid/hydrogen peroxide solution - you can buy this as a kit in most woodworking stores as "wood bleach". After you're done bleaching, you can then change the color to whatever you want with dyes or pigments.

[roman fedyk]

I believe in this months FWW they have a method of finishing Mahogany using General Finishes Gel stain. Gel stain is a good way to smooth out the color differences.

[Craig Reynolds]

FYI on color variations in Mahogany. While McPhillips recently closed, this is still a good read:

http://www.mcphillipsmfg.com/Default...arketInfo'


Sapwood in Mahogany would be greyish-white in color.

[Jeff Monson]

Potassium dicromate is a great way to darken mohagonay, care must be taken when using this chemical but it is a very effective way to get the exact shade you will like.

I usually follow the pd with linseed oil, followed by a topcoat.

[Frank Drew]

Thanks for the link to the McPhillips essay on Mahogany, Craig; some interesting information, there.