causing purpleheart to turn purple

[J. Clarke]

Way cool.

[Alan W]

Another source, woodcentral.com, suggested a remebered magazine article that muratic acid (HCL) is capable of causing the change. Might have to make a trip to the BORG and see how small of a container I can get.

Alan

[Nate]

Ok, results so far:

The color is clearly affected by pH. Conc. Sulfuric Acid turns it deep brown, but HCl (aka Muratic Acid, available at Ace Hardware stores in 1 liter or 1 gallon sizes) turns it redder. Ammonium hydroxide causes an immediate color change to green. Treatment of the green wood with acid returns the red color. Soaking the wood in NaHCO3, Sodium bicarbonate, aka baking soda, solution turns the wood green as well.

Now for the fun part, I took some grape juice, Welch's, for comparison. It displays the same color transitions! I need to produce some buffer solutions of known pH to narrow in on the color/pH relationship.

Another interesting bit: while cutting samples for testing on the table saw I noticed that the places that experienced friction with the blade (I should really check the alignment on that thing?) showed strong purple color, while the cleanly cut portions remained lighter colored. Odd. It could be that there is a biological thing going on here, wood is made up of cells after all, so the color must be held in the cells. Heat doesn't seem to be the factor, as touching it with a hot piece of metal simply burns it. Any other experiences with tools that affect the purple color?

[Mark & Juanita]

... snip of some neat experiments

Is it possible that there is a range of temperatures that cause the change? Perhaps something slightly below that required to burn the wood.

Another thought, how about rather than it being the heat, it is the friction from the blade?

[Dan White]

What color do you get if you mix the grape juice with the wood? Problem solved!

Sorry, someone had to say it. I've been posting your discussion in rec.sport.billiard as there are a number of people there who build cues with purpleheart.

dwhite

[Dan White]

Have you also given any thought to the post from Mr. Fanelli who is a cuemaker? He uses ultraviolet light to bring about the purple color. Maybe the same mechanism can be reproduced chemically. Ultraviolet light seems easier easy enough, though.

dwhite

[bridger]

if it was heat range or friction the color change would show up during sanding. I've never had that happen, but I'm not a big PH user....

[Nate]

I have tried to soak the wood in grape juice! It doesn't penetrate well, so all you get is a wet piece of wood. :( The UV reaction is one I plan to test, I need to get in touch with a friend who has a UV reactor set up in his lab, it's the kind used when you want to do photochemical reactions and should be definative on the effect. It seems the color is not easily leached out of the wood, conc. sulfuric acid seems to work, but any of the non polar solvents don't seem to do anything. I am thinking about boiling methanol, since methanol is "wood alcohol."

[Todd Rich]

It is a specific range of heat. If you carefully apply heat you can it to change color.

[Alan W]

I nuked a piece for a few minutes, it did turn a bit purple where the towel concentrated heat and moisture. It did however, also mostly burn in the same area. I have this piece sitting on my office floor and there is a marked difference in the two pieces of wood it is made up of.

Alan

[Nate]

I did some research in to the old chemical literature, it seems this was actually a target of chemists in the 1930's! The chemical in question is called peltogynol, purpleheart is a peltogyne hence the name. The description of the behavior of the wood in the literature is that it is intitially redish when freshly cut, but changes to deeper purple with exposure to air and light, eventually becoming brown. The compounds in the wood were extracted by boiling sawdust in water to extract some compounds, others were extracted with ethyl acetate (aka dye preparer for leather dye) The structure of the dye was determined, but I have yet to find any information on the reaction that produces the purple color.

But, the color may be extracted in boiling ethanol, and I now have a sample of it. A description of the isolation noted that the compound undergoes a change at 200C, but decomposes at 240C. This is in agreement with my tests using a hotplate here at lab, heating it a bit does result in darker purple, heating it too much results charcoal however! I need to bring in a new piece of wood to lab to try more controlled heating to determine the most effective heating conditions. Note that 200C is about 392F so I may use the kitchen stove tonight at home to test it, since that is well with in the range of it. If the outside of the wood becomes purple, but the inside stays the same color, then we will know that it is an oxidation, the heat woulod simply accelerate the reaction. UV also can result in oxidation through a different mechansim, so the UV route may end up being gentler for finished products.

As for the color issue, it is red- brown to start then is goes purple, then if left longer it becomes a darker brown. (just restating that to clarifiy that the people who said that it gets brown with age and those that say it goes from brown to purple with aging are both right, they just aren't talking about the same brown!)

[Alan W]

Nate, fabulous information on purpleheart. I await your stove experiements. Would it be possible for the peltogne to be reapplied to a piece of purpleheart from a chemical supply house? E.g. to cause the wood to be able to change again?

Thanks Alan

[P van Rijckevorsel]

Nate schreef

• + + Surely that is not surprising?

• + +

The chemical in question is called peltogynol, purpleheart is Peltogyne hence the name. [...]

A description of the isolation noted that the compound

There is no real reason why the reaction at 200C should be the same as the well-known one (at room temperature) PvR

[P van Rijckevorsel]

Sandy schreef in

• + + That would be Haematoxylum ...

[KIM]

I was at a lumberyard yesterday for my first time. I noticed that they had tons of exotic woods, one being a 7 foot board of ebony. As I fondled it, the owner walked by and said, "I'll let you know that is a $700 piece of wood you are handling." - Wow!

I did ask if they had any purpleheart as I have been following this thread. They went and showed me a nice specimen. I also mentioned the dilemma of getting the wood to go purple and their response was to simply flame it. I think you have tried this? Their explanation was that flaming it would kill all the white pigment in the cells. Then it would turn purple.

On another note, I happened to look around at more of the exotic woods. They showed me a nice bright red, bloodwood? I was quite intrigued with the lacewood, I thought it looked a lot like a cheetah. I can't wait to get good enough in my woodworking to be able to use such nice woods.

Good luck with the purpleheart!

KIM

[Nate]

The fact that it was a target is not surprising, but that it wasa major target worked on by several very big name chemists is a pleasant surprise.

There is a reason to expect that the reaction is the same as the one at room temperature, the color is the same. The visual absorption spectra are fairly good for indentification of molecules. The simplest explanation is that the heat speeds the kinetics of the reaction that already occurs at room temperature, since this is exactly what occurs with thousands of other reactions. It is actually that there is no reason why the reaction would be different, the null hypothesis is the reaction is the same.

I doing the controlled temperature tests today, the main goals are to determine the effective temperatures, and times for color changes. The reaction should be accelerated until the temperature reaches the decomposition temperature of the product.

I am putting together a web page of the results with pictures, I'll post it shortly.

[Ed G]

Snip!!

I can't wait to get

You should use some of the cheaper exotics in your woodworking now. I'm only a beginner but I find it inspiring to see the beauty in some of the small pieces I make, using things like Lacewood, Birdseye Maple or Jatoba. Also, the beautiful wood helps to make people miss any flaws in joinery or finish, as long as they aren't too big!!!

Ed

[Nate]

I now have a preliminary webpage setup detailing some of my experiments. It doesn't cover everything I have done but represents some interesting findings. As I find more out I will add to it. If anyone has images or other information to add please let me know.

Nate

[Alan W]

I will email along some photos from last evening's work. In a nut shell, unless the piece was purple already, I experienced no older cut pieces changing from brown to purple.

Do you know if the peltogyne (sp) dye is available from any chemical supply houses?

Alan

[Nate]

here is the URL: