Replies

1. 
   saschafer | May 20, 2008 07:09pm | #1

   One minor comment: You mention that you don't need to allow the lime to slake after adding it to the water. That's because you started with hydrated (aka slaked) lime; it is already in the form of calcium hydroxide. If you had started with quicklime (calcium oxide), then you would have had to wait for it to hydrate.

   You do have to be a bit careful when getting lime from garden centers and the like. In addition to hydrated lime, which is what you want, you can also be sold ground limestone (calcium carbonate--sometimes called dolomite or dolomitic lime) which probably won't have the same effects. You're unlikely to find quicklime for sale at garden centers; it's unstable and much more hazardous to handle.

   -Steve

    

1. 
   RMillard | May 20, 2008 08:01pm | #2

   I have no knowledge of the different kinds of lime that are available, nor do I know what the lime is really used for in gardening. I bought hydrated lime, which is what was noted in the article. If there are different types of hydrated lime out there I have not seen them for sale.

   In the past I used lye to color the mahogany and it worked best if allowed to stand over night, but the lime works just as well freshly mixed and I mentioned that because I have been asked about it before.

   The slake term I used is one I picked up when I did tile work.

   Rob Millard

   http://www.americanfederalperiod.com

     

2. 
   blewcrowe | May 20, 2008 10:48pm | #3

   Rob, that's a very nice article and generous of you to share.

   Denny

   
   

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   Edited 5/20/2008 3:49 pm ET by blewcrowe

3. 
   cwalvoord | May 20, 2008 11:24pm | #4

   Thanks for the great article. I will try it out on my next mahogany project. I am curious what your process is for the last two steps - the filler and top coat. Any tips there? I usually use a tinted pore filler which, I assume, would not darken the sealed stringing. Is that your experience?
   Thanks again.
   Chris

1. 
   RMillard | May 21, 2008 12:27am | #5

   I do use oil based pore filler in a brown mahogany color, and the sealing of the inlays does keep them clean, but on pieces that have satinwood (Brazilian) inlays, I will brush on a third coat of sealer because the open pores on this wood can collect some filler and make the inlays look muddy. For top coats, I use shellac or Ultima Spray Lacquer, but I have also used  Behlen Rock Hard Varnish and brushing lacquer.

   Rob Millard

   http://www.americanfederalperiod.com

    

1. 
   JiminFla | May 22, 2008 11:57pm | #8

   Rob,

   When I finish mahogany, I normally apply the grain filler before I apply the dye.  I do this because I sand the wood lightly after the filler has dried to remove any residue that may remain.  I would think that it would be easy to sand through the finish if I apply the filler after the dye.  Your thoughts?

   Jim

1. 
   RMillard | May 23, 2008 01:23am | #9

   Jim,

   I apply the filler after the oil and the oil is enough of a barrier coat to prevent the filler from sticking to the surface. I let the filler sit until it is to the panic stage and then scrape it off with a plastic putty knife. I again let it sit for a few more minutes and wipe across the grain with burlap. Then I let it sit a few more minutes and buff with the grain using cheese cloth, and this removes every bit of filler, but that in the pores. I have on occasion, buffed the surface with a synthetic abrasive pad, before applying the topcoat, just to be sure I don't have any filler on the surface, but this was before I starting letting the filler really set up, before removing it.

   I have heard of applying water based filler to the raw wood and then using the dye, but I have not used water based fillers.

   Rob Millard

   http://www.americanfederalperiod.com

1. 
   dkellernc | May 23, 2008 10:17pm | #10

   Rob - I too have done a great deal of experimenting with coloring mahogany to make it look like it's 200+ years old.  I used to use calcium hydroxide (lime), and I've a suggestion:  The lime that garden centers have is not very pure or controlled from batch to batch, and it typically has other minerals in it as impurities.  The equivalent for woodworkers is using tap water to mix up water-based dyes and colorants.  Sometimes you can get away with this, but sometimes there's sufficient manganese and other divalent metals in the water to do very strange things to aniline dyes and ebonizing compounds.

   You can get purified Calcium Oxide (albiet at a higher price) from any tropical fish store that specializes is coral reef aquariums.  You can also get it at http://www.thatpetplace.com.  It's typically sold as "Kalkwasser" (German for lime water), and is in the powdered form.  It's calcium oxide, but once you add it to water it instantly reverts to the calcium hydroxide form.  Naturally, the aquarium companies take reasonable pains to package relatively pure calcium oxide, so you don't get as much variation batch to batch.

   However, I'm curious - why bother with the lime if you're going to use aniline dye to tweak the color anyway?  That's why I gave up the lime and lye routine - using a mixture of Transtint Brown Mahogany and Red Mahogany gives a nice, rich color, and instantly obliterates any difference in color matching between the boards.

   I'm even thinking of giving up on the dye as well - I've found that a combination of a couple of days in direct (i.e., outdoors) sunlight and linseed oil dramatically darkens mahogany, and there's no chance of drips or runs that give away a dye job.

2. 
   RMillard | May 23, 2008 11:12pm | #12

   So far I have not experienced any problems with the bags of lime I have purchased from various sources, but I will look into the lime from the link you provided (thanks).

   As to the question about the use of dyes and the lime. The lime locks in the color; it will not change much at all over time. I still cringe when I think of the pieces I dyed fairly dark and how they have gotten too dark now. Also the lime builds in most of the color, making it an easy chore to seal the inlays. Before the lime method, I would seal the inlays and then apply the dye; this was quite difficult and the results were less than spectacular.

   I have heard ( and once used) the sun idea, but I find it too risky for some pieces (a card table comes to mind, where the top could warp all out of shape with the exposure to the sun) and too variable for large pieces, where the light wouldn't fall evenly. I used it on a firescreen panel where there was no chance of warping and its size made it a sure thing. The results were nice, but I think it lacked the beauty of the lime method.

   Rob Millard

   http://www.americanfederalperiod.com

   Edited 5/23/2008 5:40 pm ET by RMillard

3. 
   dkellernc | May 24, 2008 06:03pm | #13

   Rob -

   A thought on the sun method.  It's true that the light doesn't fall evenly on a large piece, but I generally leave it out all day for several days, and the movement of the sun provides insurance against any hard lines that might result from a light source at a constant angle.

   There's a way, however, to avoid having to place a piece outside and potentially have issues with humidity changes, bird droppings, etc...  Also taken from the reef-tank aquarium field is the idea of using an artificial UV source in the form of a metal halide lamp.  These lamps are intentionally constructed to output very large amounts of UV, as they're designed to replicate the spectrum of the equitorial sun where corals are found.  They're fairly inexpensive in the just-a-fixture (i.e., no aquarium hood) form. 

   I'm still experimenting with one of these, but so far they work very well in darkening honduran mahogany in a controllable fashion, and do seem to even out color differences between different boards.  I intend to write up these results for the SAPFM journal, though it's debateable whether I'll make the press deadline this year.

4. 
   RMillard | May 24, 2008 07:13pm | #14

   I'd like to hear more about this when you finish.

   I have thought about the lights, (although I was thinking tanning bed type lights) but I wasn't sure if they put out too much heat. It is the heat and the other uncontrolled factors that you mentioned that make the sun less than appealing to me.

   Rob Millard

   http://www.americanfederalperiod.com

5. 
   JiminFla | May 23, 2008 10:24pm | #11

   Thanks for the advice, Rob.  I will try this on my next mahogany project.

   Jim

4. 
   Glaucon | May 21, 2008 06:49pm | #6

   Very nice site, and a good, useful article.

   Thanks Rob,

   Glaucon

   If you don't think too good, then don't think too much...

5. 
   pzaxtl | May 22, 2008 06:16pm | #7

   Hey Rob,

   Thanks, heaps, for the info!  Lately, I've taken to fuming mahogany with ammonia, but it looks as though your methodology will produce nearly the same color with less concerns for toxicity.  I'm going to give it a try.