I have a project with part of one board which will not turn purple:
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layer with the routed compartment below the lid, on the left side it is still very brown, it is getting purple in the middle of the compartment and quite purple on the right hand side of the box.
The box has been air exposed for a number of months now and is NOT purple when sanded or cut. The particular purpleheart I purchased is brown first then oxidizes to purple. Except this part of one piece.
What other methods are known to transition purpleheart. I've tried sun exposing a scrap piece of the same brown source wood, it will not turn either. I'm about to put the whole thing in the oven, has anyone baked purpleheart purple yet?
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to show all purpleheart is not created equal, two turned brown, one much less so, tape to show the difference.
Does someone have a forest service expert for a relative?
have you tried any chemical approaches? I don't know the chemistry of purple heart turning purple, but lots of woods respond to alkali and acid by changing color. I'd start with a paste of baking soda, rubbing it on a scrap....
On Tue, 18 May 2004 20:18:01 -0700, snipped-for-privacy@thanks.com posted:
That's an interesting tack.
Some of those colours act as "indicators" changing colour with different pHs and also with oxidation or reduction.
You could try the baking soda for the alkaline, and then maybe vinegar or lemon juice for an acid treatment.
Then to oxidise, you could try household bleach, and to reduce, some oxalic acid solution (caution -- toxic). You could also try these in acid and alkaline conditions. Ammonia might also be interesting.
I've got a bottle of haematoxylin which is the extract of some South American tree that I can't quite name at the moment.
It is reddish in acid environment and bluish purple in alkaline IIRC from 40 years ago. I am going to experiment with that on some bland boring wood sometime. I have a 12' x 14" poplar log drying in the shed at the moment that might be interesting to try things on. I just scored a street-tree log that was hollow and met the chain-saw-and-chipper-brigade this morning. It has some very interesting grain patterns next to the hollow section. It will be interesting to split it in a few years and run it over the jointah. Oh, its a London Plane BTW.
I have some rosewood and other stains that are excellent for colour matching my jarrah when needed.
I also intend to experiment with strong black tea on piney wood. I've tried the other solvent-based stains with rather poor results, being rather blotchy. Piney wood can be a real challenge at times, but when a clear length has those straight grains close together, it is stronger than steel, weight for weight.
The best wooddorking book I ever read from cover to cover was George Frank's Adventures in Wood Finishing. I see there is a new edition out with Bruce Hoadly. Now that seems a must read for those interested in the science of wood finishing :)
On Thu, 20 May 2004 05:28:23 GMT, "Dan White" posted:
I haven't received this message in full, just what Dan quoted. That's interesting that lemon juice had an effect, but vinegar didn't, indicating that perhaps it is not a pH colour change but something specific to the lemon juice. Now lemon juice has vitamin C in it (ascorbic acid which is a reducing agent as well). I would be very interested in the effect of oxalic acid (a strong reducing agent) on the wood. And then perhaps oxalic acid and lemon juice and another test with oxalic acid (COOH)2 and baking soda. The purple may in fact be something that we won't be able to control. Does Hoadley ever mention this wood in his learned tomes? Perhaps one of you guys could email him and ask. In a lab I once worked in in a previous life we sometimes "washed out" stains with "acid alcohol" which was just alcohol (methylated spirit, denatured ethanol or ?rubbing alcohol) with a few drops of hydrochloric acid in it. Wouldn't it be great if you guys with access to purple heart could wash the stain out of scrap and either apply it or sell it? :) BTW, oxalic acid might be obtainable as a radiator cleaner, and it is toxic. Talking of toxic, I wonder what the toxic potassium dichromate, a powerful oxidising agent, might do to this interesting wood. It has some pleasant effects on other woods, IIRC.
I've never used Oxalic acid, but could you use a paste of "Bar Keepers Friend" as a less toxic application of it? It's main ingredient is Oxalic acid 10% and is only a couple of bucks at wal-mart. MSDS:
Alan: I posted your question over on rec.sport.billiard which I frequent, and which has several cue makers who are familiar with purpleheart wood. These are the responses received today. All of the posts below except the last one were written before I posted your original post with the pics and all. You may get other responses so you might want to check out that newsgroup.
good luck,
dwhite
1)
I believe the sun is what causes the browning. I think a light sanding and refinishing would be best. Use some finish that shield UV rays.
Tracy
2)
It is the sun that caused the color change to start. When PH is exposed to UV, the nice color goes away. Depending on how badly the color has gone, a light sanding 'might' bring back some of the color. As a last resort, go to the art store and buy some pigment the same color as the good PH. Mix with clear oil and apply very very very very very thin layers, wait until each layer dries (about a day), and apply until happy with the color. This technique is called glazing. But again, only a last resort because it is easy to screw up. Deno
3)
Sometimes that can be a tough one depending on the wood quality. I have had Purple Heart wood that turned brown and some that stayed a bright purple from start to finish. About the only other thing he might try is heat. I use a hot air gun (no jokes please ) sometimes to deepen the purple color. I dont know about chemicals as the only methods I have used are hot air and/or time under a florescent light.
William Lee
In response to Adam's post:
4)
Adam:
This is the first I have heard of such a wood. Normally it is the exact opposite.
On 20 May 2004 08:36:52 -0700, snipped-for-privacy@kreusch.com (Jay) posted:
Can't see why not, if that's what's in it. Looks like there is detergent and perhaps a scourer. I'd try to dissolve the stuff and let any insoluble stuff settle out and use the clear solution.
The detergent should wash away, but will help the oxalic acid penetrate the wood. Give it a try, if it doesn't do anything to the wood, you have a good bath cleaner :)
It's also pretty nasty stuff and hard to dispose of safely.
Oddly enough, folks who use "natural dyes" because they're environmentally safe, soak their wool in all kinds of very toxic "mordants" in order to prepare them for taking and holding "natural" dye. Sulfuric acid and a Potassium Dichromate solution were just two of the things I found after divorcing a "natural" spinner, dyer, weaver. The garbage bags of onion skins, crushed walnut shells and bard and rotting flowers were much easier to safely dispose of.
Unless you know what you're doing and how you're going to safely dispose of chemicals - leave them alone - please.
On Fri, 21 May 2004 17:07:32 -0700, charlie b brought forth from the murky depths:
Hopefully, most people will keep the label attached and already know about the thousands of hazardous waste facilities in this country which accept it freely. Alternatively, the guys could recycle the chemicals to the rest of us Wreckers. Just ask!
I'm looking for some fuming ammonia right now.
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Yep, a couple months of sitting and the rest of the purpleheart has gone more purple, but 3" of one of the boards won't change over.
This evening I placed a fresh cut off from the scrap into a plastic bag with some household ammonia in it. Effect was immediate of a yellowing of the wood. It did not matter if it was months old, sun exposed, or freshly cut on this scrap piece, it had a definite yellow cast.
If the T-showers stop long enough tomorrow to get strong sunlight, I will take another reference photo to post up.
So do I! As luck would have it I happen to be a dye chemist with access to all sorts of chemicals and tools for analyzing chemicals. And I happened to pick up a chunk of Purpleheart.
My plan is to collect the dust from sanding the Purpleheart, then extract it with a solvent (which one I will have to determine, depends on what gets the color to disolve, but I have like 40 choices so I'll find one.) I will then purify the compound that is colored, and run some chemical tests on it (NMR, IR, UV/Vis, perhaps even a GC/MS.) Hopefully after that I will be able to report on the nature of the chemical.
Don't want to wait? Well, my best guess is that the color comes from a anthocyanin, similar to the the compund giving grape juice it's color. UV light probably makes it turn brown by activation of the molecule to oxidize with atmosphereic oxygen. I'm test it with various acids and bases as well to see if the color is sensitive, and if the reaction is reversable. (Cherry juice is actually changes color with pH, acting as an indicator, as do a number of colors fround in plants.)
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