French polish: blue/green color on muneca

[Bob Gramann]

For years, I have noticed a blue/green coloration on my pad when I leave it in the jar for a few days. It seems to cause no problems. Anybody know what it is?

[Randy Roberts]

Bob,

What are you using as your solvent?
Are you using a rubber band to secure the muneca covering?
Are you noticing any hint of the color accumulate on a new muneca while you use it, that it might be coming from the wood or dyed purfling, etc?
Any colored contaminants in your flakes?
What is the seal on the lid of your jar look like, that the colorant might be leaching from it?
Are you by any chance using surgical sponge cotton gauze for the inside pad of the munica? Those will usually have a dyed thread somewhere in the weave that allows detecting a forgotten sponge inside the patient in a post-surgical x-ray, and I suppose that might be vulnerable to leaching some dye out of the thread with an alcohol based solvent.
And, I guess, as a last stab at it, how long since your last eye exam? <g>

I've only ever had the stain from wood pigments, or the pale yellow brown build up of the shellac on the muneca cover that I can recall...

[Bob Gramann]

It’s weird. I’m using a piece of a microfiber rag on the outside and wool on the inside. It also occurred with old cotton T-short pieces. No rubber band. It’s been happening for many years both with stacked brown wool fabric and with a wadded up black and blue sock. I would suspect the sock if it weren’t for it happening with the brown wool. It’s only on the outside of the outer fabric. It develops when the pad is in the jar for a few days unused. I traded jars to see if maybe there was copper in the top that was leaching out. The new jar top is resin-lined. No difference. I’m using Everclear 190 for the solvent and pale blonde shellac flakes. I can’t remember if I got this batch from Vijay or from LMI, but it has happened across batches. I would consider dyes in the purfling except that it isn’t visible when I finish a session, only a few days later. I keep my shellac in a clear HDPE plastic bottle.

I figured there was a chemistry lesson in here somewhere if someone knew enough to teach me. It has me stumped.

[Randy Roberts]

Found this from a research paper on toxicity of microfibers in marine environments...

"In addition to the effects of the microfibers themselves, various additives are incorporated into fibers during textile production to enhance performance, including antibacterial agents, flame retardants, dyes, plasticizers, antistatic agents, and antioxidants [26]. These substances are generally weakly bound to the fibers and can be leached into the environment [27]. Besides being a primary source of toxic agents already present in their formulation, MFs can also adsorb a wide range of contaminants from the surrounding environment, such as toxic metals and organic pollutants like PAHs, DDT, PCBs, and dioxins [28]. However, significant gaps remain in understanding the effects of MFs on marine invertebrates [29]."

Now I know the reason the shrimp I had for supper tonight tasted a little off was thanks to your french polish technique.

The thing that makes microfiber cloth so great for cleaning stuff is that the chemical structure of the fiber creates tons of little pockets that adhere damn near anything with a slight negative charge by way of Van der Waal forces, which are weak electrical charges. Because it isn't a chemical bond formed, anything adhering in the microfiber can leach back out fairly easily.

Although I am not in any way a chemist, I did have to take 2 semesters of organic chemistry as a prequisite for Vet School, unfortunately all I got out of it was a cure for insomnia.

[Bob Gramann]

Wow! Thank you. That might explain why it blooms over a couple of days. It doesn’t explain what leaches back out (but that sure looks like it has copper in it). Tell your shrimp to lighten up. I’ve never thrown one of my guitars into the ocean.

Since the color is on the outside of the pad, perhaps it came off of the guitar. That adds my saw blades and sandpaper as suspects for the source. I may do some experimenting.

And then, there’s the pumice and the woods.

[Bryan Bear]

I'm far from a chemist, so I can't really offer much. But, to muddy the waters, are you wearing gloves when you FP? Just wondering if there is potentially a body chemistry thing happening (not implying that you are drunk from absorbing the everclear <G>).

[Randy Roberts]

Brian,
Good point! The cheap nitrile gloves I use are a light blue color (I'm green/red color blind so they might be blue green?). The microfiber might be picking up pigment from the gloves, then leaching it back out?
Bob,
If you aren't using gloves, and it's body chemistry from something being picked up when you tap the munica on the back of your hand to disperse the shellac in the pad, it could be any of hundreds of organic compounds. (Do you detect a hint of blue green when you look in the mirror?) A good test would be filling the bathtub with solvent and soaking for a few days.
And if you have Dalmation, Bedlington, or West Highland White Terrier in your ancestry, you might have a genetic predilection for excessive storage of copper in the liver called copper-associated hepatopathy. (Brian, we might be able to really get Bob wound up persuing this line of reasoning).

[Bob Gramann]

All interesting suggestions. Now, I’m wearing black nitrile gloves. Years ago, when I first noticed the issue, I usually worked bare-handed (well, bare hands with some shellac coating).

A bath tub full of Everclear would be a frightening proposition. It wouldn’t take much to ignite the fumes. Alcohol does make a nice blue flame. And, the canine ancestry could certainly put the “Woof!” into the ignition.

When I first posted the question, I was wondering if the phenomenon was common enough that someone else had seen it. One wood I commonly work with is Osage Orange. Now, I’m wondering if there’s a blue component of the coloring in that wood. Soaking some fragments in alcohol might answer that question. I’ll report after the experiment.

[Bryan Bear]

Back in college I got exposed to so much of the solvent Bob is using that I felt like I needed to soak in a bathtub for a few days. I was sick as an West Highland white terrier as they say.

[Bob Gramann]

I did some search engine research. Osage Orange contains a yellow dye called maclurin. This dye turns green in the presence of ferric chloride. I can imagine some iron filings and some sweat in my workshop. There easily could be iron in the granules of my sandpaper. I don’t know how much of each it would take to get the reaction, but there appears to be a path to the color I see with the stuff I am using. Better living through chemistry!

[Dave Rickard]

Currently I’m really focusing on French polish. Looking back at notes from ASIA gatherings from several years ago the best advice I was given besides “ya need to rub on that some more” was to us new cloth, why spend all the time and effort on a French polish and not use new material for your finishing pad. Go to a fabric store the cost is not really that much. It may not solve the problem you’re having but I thought I’d throw it out there.

[Bob Gramann]

I use the same wool interior forever. The shell gets moved to a new area as it wears and then gets replaced when it’s all used up. Thanks.